# Smoking Prevalence among Physicians: A Systematic Review and Meta-Analysis

Anaïs Besson, Alice Tarpin, Valentin Flaudias, Georges Brousse, Catherine Laporte, Amanda Benson, Valentin Navel, Jean-Baptiste Bouillon-Minois, Frederic Dutheil

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## To cite this version:

Anaïs Besson, Alice Tarpin, Valentin Flaudias, Georges Brousse, Catherine Laporte, et al.. Smoking Prevalence among Physicians: A Systematic Review and Meta-Analysis. International Journal of Environmental Research and Public Health, 2021, 18 (24), pp.13328. 10.3390/ijerph182413328. hal-03661639

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Review

# Smoking Prevalence among Physicians: A Systematic Review and Meta-Analysis

Anaïs Besson <fnref n="1" />,†, Alice Tarpin <fnref n="1" />,†, Valentin Flaudias <fnref n="2" /> ID, Georges Brousse <fnref n="3" />, Catherine Laporte <fnref n="3" /> ID,
Amanda Benson <fnref n="4" /> ID, Valentin Navel <fnref n="5" /> ID, Jean-Baptiste Bouillon-Minois <fnref n="6" />,* ID and Frédéric Dutheil <fnref n="7" /> ID

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**Citation:** Besson, A.; Tarpin, A.; Flaudias, V.; Brousse, G.; Laporte, C.; Benson, A.; Navel, V.; Bouillon-Minois, J.-B.; Dutheil, F. Smoking Prevalence among Physicians: A Systematic Review and Meta-Analysis. *Int. J. Environ. Res. Public Health* **2021**, *18*, 13328. https://doi.org/10.3390/ijerph182413328

Academic Editor: Aziz Rahman

Received: 24 November 2021

Accepted: 15 December 2021

Published: 17 December 2021

**Publisher's Note:** MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations.

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**Copyright:** © 2021 by the authors.
Licensee MDPI, Basel, Switzerland.
This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https://creativecommons.org/licenses/by/4.0/).

**Abstract:** Background: Smoking is a major public health problem. Although physicians have a key role in the fight against smoking, some of them are still smoking. Thus, we aimed to conduct a systematic review and meta-analysis on the prevalence of smoking among physicians. Methods: PubMed, Cochrane, and Embase databases were searched. The prevalence of smoking among physicians was estimated and stratified, where possible, by specialties, continents, and periods of time. Then, meta-regressions were performed regarding putative influencing factors such as age and sex. Results: Among 246 studies and 497,081 physicians, the smoking prevalence among physicians was 21% (95CI 20 to 23%). Prevalence of smoking was 25% in medical students, 24% in family practitioners, 18% in surgical specialties, 17% in psychiatrists, 16% in medical specialties, 11% in anesthesiologists, 9% in radiologists, and 8% in pediatricians. Physicians in Europe and Asia had a higher smoking prevalence than in Oceania. The smoking prevalence among physicians has decreased over time. Male physicians had a higher smoking prevalence. Age did not influence smoking prevalence. Conclusion: Prevalence of smoking among physicians is high, around 21%. Family practitioners and medical students have the highest percentage of smokers. All physicians should benefit from targeted preventive strategies.

**Keywords:** tobacco; smoking; physician; doctor; prevalence

## 1. Introduction

Smoking is a major public health problem [1]. According to the International Classification of Diseases (ICD-10), tobacco smoking disorder is considered a mental and behavioral disease [2]. Furthermore, according to the World Health Organization, there are about a billion smokers around the world and tobacco kills more than seven million of them per year [1]. Tobacco control has been present in many countries for several years. In 2003, the WHO adopted the Framework Convention on Tobacco Control. Despite their

<footnote n="1">1 Family Medicine, University Hospital of Clermont-Ferrand, Université Clermont Auvergne, F-63000 Clermont-Ferrand, France; bessona.ab@gmail.com (A.B.); alice.tarpin@gmail.com (A.T.)</footnote>

<footnote n="2">2 Univ Angers, Laboratoire de psychologie des Pays de la Loire, Université de Nantes, LPPL, EA 4638, F-44000 Nantes, France; valentin.flaudias@univ-nantes.fr</footnote>

<footnote n="3">3 Clermont Auvergne INP, CHU Clermont-Ferrand, CNRS, Institut Pascal, Université Clermont Auvergne, F-63000 Clermont-Ferrand, France; gbrousse@chu-clermontferrand.fr (G.B.); catherinelaporte63@gmail.com (C.L.)</footnote>

<footnote n="4">4 Sport Innovation Research Group, Department of Health and Biostatistics, Swinburne University of Technology, Melbourne, VIC 3122, Australia; abenson@swin.edu.au</footnote>

<footnote n="5">5 CNRS, INSERM, GReD, Translational Approach to Epithelial Injury and Repair, CHU Clermont-Ferrand, Ophthalmology, Université Clermont Auvergne, F-63000 Clermont-Ferrand, France; valentin.navel@hotmail.fr</footnote>

<footnote n="6">6 CNRS, LaPSCo, Physiological and Psychosocial Stress, University Hospital of Clermont-Ferrand, Emergency Medicine, Université Clermont Auvergne, F-63000 Clermont-Ferrand, France</footnote>

<footnote n="7">7 CNRS, LaPSCo, Physiological and Psychosocial Stress, University Hospital of Clermont-Ferrand, Occupational and Environmental Medicine, Université Clermont Auvergne, WittyFit, F-63000 Clermont-Ferrand, France; fdutheil@chu-clermontferrand.fr</footnote>

<footnote>* Correspondence: jbb.bouillon@gmail.com; Tel.: +33-6-74-36-04-23; Fax: +33-4-73-27-46-49</footnote>

<footnote>† Contributed equally.</footnote>
knowledge of the health risks linked to smoking [3], some physicians smoke too [4,5]. Prevalence of smoking among physicians can be a public health issue both for themselves and for patients because they play a key role in combating tobacco use [6]. Indeed, it has been demonstrated that physicians who smoke are less likely to promote quitting smoking to their patients [7,8]. However, the prevalence of smoking among physicians has not recently been systematically reported in the literature. Moreover, some medical specialties may be particularly at risk of smoking, due to workload [9] or work conditions [10], for example. In addition, a country's culture or wealth can influence the perception of smoking [11,12]. Lastly, the perception of smoking has, historically, changed considerably [13], from a rewarding to a negative image [14]. Although there is a dense literature on the impact of tobacco smoking on health among general population, we did not find any systematic review and meta-analysis on smoking among physicians.

Therefore, we aimed to conduct a systematic review and meta-analysis on the prevalence of smoking among physicians. Secondary objectives were to report physicians' smoking prevalence depending on their specialties, to investigate differences between countries, changes over time and putative effects of sociodemographic factors.

## 2. Materials and Methods

### 2.1. Literature Search

We reviewed all studies reporting the smoking prevalence among physicians. Eligible articles had to appear on the PubMed, Cochrane Library, Embase, and ScienceDirect databases with the following keywords: "smoking" and "physician" (or "doctor") and "prevalence". The search was conducted up to May 2021 (details for the search strategy used within each database are available in Appendix A. Studies could be cross-sectional studies, cohort studies, or clinical trials. The search was not limited to specific years. We limited our search to English or French articles. To be included, studies needed to describe our primary outcome variable, i.e., the prevalence of smoking among physicians. Two authors (Anaïs Besson and Alice Tarpin) conducted the literature searches, reviewed the abstracts, and, based on the selection criteria, decided the suitability of the articles for inclusion and extracted the data. When necessary, disagreements were solved with a third author (Frédéric Dutheil). We followed the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines [15].

### 2.2. Data Extraction

The primary outcome analyzed was the smoking prevalence and type of smoking (occasional or regular) among physicians. Secondary outcomes reported medical specialty, continent, study's period, ex-smoking prevalence, sociodemographic parameters (age, gender, family status, and workplace setting), workload (mean duration week), clinical parameters (body mass index and physical activity behavior), and smoking prevalence among a population control.

### 2.3. Quality of Assessment

We used the Newcastle-Ottawa Scale (NOS) to check the quality of included articles [16]. The maximum score was nine for cohort and ten for cross-sectional studies. Additionally, we also used the Strengthening the Reporting of Observational Studies in Epidemiology (STROBE) for cohort and cross-sectional studies [17], and the Consolidated Standards of Reporting Trials (CONSORT) for randomized studies [18] (Appendix B).

### 2.4. Statistical Considerations

Statistical analysis was conducted using Stata software (v16, StataCorp, College Station, TX, USA). Extracted data were summarized for each study and reported as mean (standard deviation) and count (%) for continuous and categorical variables, respectively. Prevalence of smokers and 95% confidence intervals were estimated using random-effects models assuming between and within study variability (DerSimonian and Laird approach) [19].
Then, we stratified results depending on specialties, continents, and periods of time. Statistical heterogeneity between studies was assessed using forest plots, confidence intervals, and I². The I² statistic is the most common metric to measure heterogeneity and is easily interpretable: heterogeneity is considered low for I² < 25%, modest for 25–50%, and high for >50% [20]. We aimed to conduct a sensitivity analysis by excluding studies not evenly distributed around the base of the metafunnel. We also proposed meta-regressions to investigate putative factors influencing the prevalence of smoking in physicians, such as sociodemographic (age, sex), specialties, continents, and periods of time. Results were expressed as regression coefficients and 95% confidence intervals. Type I-error was fixed at α = 0.05.

### 3. Results

An initial search produced 3112 possible articles. Removal of duplicates and use of the selection criteria reduced the number of articles reporting the smoking prevalence among physicians to 246 articles (Figure 1). Main characteristics of the studies are presented in Table 1.

<figure><img src="image_6.png" /><figcaption>**Figure 1.** Flow chart. Three databases were asked (PubMed, Cochrane, and Embase). Over 3112 eligible articles, 246 were included. Stratification was performed by specialty, by continent, and by time period. *: details for the search strategy used within each database are available in Appendix A.</figcaption></figure>
<table><caption>Table 1. Characteristics of included studies.</caption><thead><tr><th rowspan="2">Study</th><th rowspan="2">Country</th><th rowspan="2">GDP per Capital</th><th rowspan="2">Period of Data Collection</th><th colspan="4">Physicians</th><th colspan="2">Prevalence (%) of</th><th colspan="2">Smokers</th><th rowspan="2">Total (Regular & Occasional)</th><th rowspan="2">% Men among Smokers</th></tr><tr><th>n</th><th>% Men</th><th>Age</th><th>Speciality</th><th>Regular Smokers</th><th>Occasional Smokers</th><th>Former Smokers</th><th>Total (Regular & Occasional)</th></tr></thead><tbody><tr><td>Aaro 1977</td><td>Norway</td><td>6812</td><td>1952–1974</td><td>3544</td><td></td><td></td><td>Not defined</td><td></td><td></td><td></td><td>58.3</td><td>92.5</td></tr><tr><td>Abdullah 2006</td><td>China</td><td>1149</td><td>2002</td><td>757</td><td>78.2</td><td></td><td>Not defined</td><td></td><td>2.1</td><td></td><td>4.3</td><td></td></tr><tr><td>Aboyans 2009</td><td>France</td><td>41,508</td><td>2007</td><td>371</td><td>49.8</td><td></td><td>Cardiology</td><td></td><td>32.4</td><td></td><td>8.1</td><td></td></tr><tr><td>Akvardar 2004</td><td>Turkey</td><td>6041</td><td></td><td>319</td><td></td><td></td><td>Study, Others</td><td></td><td></td><td></td><td>37.6</td><td></td></tr><tr><td>Al Alwan 2013</td><td>Saudi Arabia</td><td>16,094</td><td>2009</td><td>100</td><td></td><td></td><td>Not defined</td><td></td><td>7</td><td></td><td>12</td><td></td></tr><tr><td>Alarjan 2015</td><td>Jordan</td><td>4096</td><td></td><td>162</td><td></td><td></td><td>Not defined</td><td></td><td></td><td></td><td>34.0</td><td></td></tr><tr><td>Al-Khateeb 1990</td><td>Bahrain</td><td>7959</td><td>1988</td><td>301</td><td></td><td></td><td>Not defined</td><td></td><td>8.6</td><td></td><td>60.1</td><td></td></tr><tr><td>Al-Lawati 2009</td><td>Oman</td><td>16,784</td><td></td><td>1079</td><td></td><td></td><td>Family medicine, Biology, Others</td><td></td><td></td><td></td><td>22.2</td><td>97.5</td></tr><tr><td>Allan 1976</td><td>Australia</td><td>7475</td><td></td><td>1153</td><td></td><td></td><td>Family medicine, Radiology, Pathology, Anesthesiology-Reanimation, Gynecology, Others</td><td></td><td></td><td></td><td>14</td><td></td></tr><tr><td>Al Shahrani 2021</td><td>Saudi Arabia</td><td>23,338</td><td>2018</td><td>290</td><td>59.7</td><td></td><td>Not defined</td><td></td><td></td><td></td><td>34.8</td><td>70.3</td></tr><tr><td>Amara 2008</td><td>Morocco</td><td>2885</td><td>2007</td><td>75</td><td>44.4</td><td></td><td>Pneumology</td><td>37.5</td><td>62.5</td><td>12</td><td>10.7</td><td></td></tr><tr><td>Amte 2015</td><td>India</td><td>1606</td><td></td><td>242</td><td>84.7</td><td>37.9</td><td>Not defined</td><td>36.4</td><td>63.6</td><td></td><td>13.6</td><td></td></tr><tr><td>An 2004</td><td>USA</td><td>36,334</td><td>2000</td><td>750</td><td>68.9</td><td></td><td>Not defined</td><td></td><td>16.9</td><td></td><td>1.5</td><td></td></tr><tr><td>Arnetz 1988</td><td>Sweden</td><td>24,189</td><td></td><td>66</td><td>100</td><td>43.9–46.8</td><td>Family medicine, Others</td><td></td><td>23.3–33.3</td><td></td><td>22.7</td><td>100</td></tr></tbody></table>
<table><caption>Table 1. *Cont.*</caption><thead><tr><th rowspan="2">Study</th><th rowspan="2">Country</th><th rowspan="2">GDP per Capital</th><th rowspan="2">Period of Data Collection</th><th colspan="4">Physicians</th><th colspan="2">Prevalence (%) of Smokers</th><th colspan="2">Smokers</th><th rowspan="2">% Men among Smokers</th></tr><tr><th>n</th><th>% Men</th><th>Age</th><th>Speciality</th><th>Regular Smokers</th><th>Occasional Smokers</th><th>Former Smokers</th><th>Total (Regular & Occasional)</th></tr></thead><tbody><tr><td>Aryayev 2014</td><td>Ukraine</td><td>3105</td><td></td><td>150</td><td>31.3</td><td></td><td>Family medicine, Paediatry, Study</td><td></td><td></td><td></td><td>42</td><td>61.9</td></tr><tr><td>Baltaci 2014</td><td>Turkey</td><td>10,672</td><td>2010–2011</td><td>1233</td><td>57.1</td><td>38.94</td><td>Not defined</td><td></td><td>14.8</td><td></td><td>34.1</td><td></td></tr><tr><td>Baptista 1993</td><td>Venezuela</td><td>2368</td><td>1990</td><td>191</td><td>49.7</td><td>31</td><td>Not defined</td><td></td><td></td><td></td><td>20.9</td><td></td></tr><tr><td>Barengo 2004</td><td>Finland</td><td></td><td>1990–2001</td><td>4546</td><td>51.4</td><td></td><td>Not defined</td><td>38.1</td><td>61.9</td><td></td><td>16</td><td></td></tr><tr><td>Barengo 2005</td><td>Finland</td><td>24,913</td><td>2001</td><td>707</td><td></td><td></td><td>Family medicine</td><td></td><td></td><td></td><td>12.7</td><td></td></tr><tr><td>Barnoya 2002</td><td>Guatemela</td><td>1702</td><td>2002</td><td>174</td><td>56.9</td><td></td><td>Not defined</td><td></td><td></td><td>35</td><td>17.8</td><td>56.9</td></tr><tr><td>Basnyat 2000</td><td>UK</td><td>28,015</td><td>1998</td><td>314</td><td>97.8</td><td>51</td><td>Not defined</td><td></td><td></td><td>37</td><td>10.2</td><td>97.8</td></tr><tr><td>Basu 2011</td><td>India</td><td>1346</td><td>2010</td><td>182</td><td></td><td></td><td>Study</td><td>85.5</td><td>14.5</td><td></td><td>30.2</td><td></td></tr><tr><td>Behbehani 2004</td><td>Bahrain, Kuwait</td><td></td><td>2000–2001</td><td>1440</td><td>66.5</td><td>44.6–44.7</td><td>Not defined</td><td>62.1</td><td>37.9</td><td>14.3–15.9</td><td>17.2</td><td>92.7</td></tr><tr><td>Belkić 2007</td><td>Serbie</td><td>2150</td><td>2002–2004</td><td>112</td><td>0</td><td>48.9</td><td>Not defined</td><td></td><td></td><td>12.5</td><td>31.3</td><td>0</td></tr><tr><td>Belkić 2012</td><td>Serbie</td><td>2150</td><td>2002–2004</td><td>191</td><td>42.9</td><td></td><td>Not defined</td><td></td><td></td><td></td><td>30.4</td><td>39.7</td></tr><tr><td>Bener 1993</td><td>Kuwait, United Arab Emirates</td><td></td><td>1990–1992</td><td>527</td><td></td><td></td><td>Not defined</td><td></td><td></td><td>12.7–13.5</td><td>37</td><td></td></tr><tr><td>Borgan 2014</td><td>Bahrain</td><td>24,737</td><td>2013</td><td>148</td><td>33.8</td><td>45</td><td>Not defined</td><td></td><td></td><td>3.9</td><td>10.1</td><td>80</td></tr><tr><td>Bortz 1992</td><td>USA</td><td>25,493</td><td></td><td>126</td><td>77.8</td><td></td><td>Not defined</td><td></td><td></td><td>22.2</td><td>1.6</td><td>100</td></tr><tr><td>Bostan 2015</td><td>Turkey</td><td>10,672</td><td>2010–2011</td><td>699</td><td></td><td>38.7</td><td>Pneumology</td><td></td><td></td><td>19.5</td><td>9.9</td><td></td></tr><tr><td>Bourke 1972</td><td>Ireland</td><td>1152</td><td>1967–1969</td><td>1580</td><td>86</td><td></td><td>Not defined</td><td></td><td></td><td>23.6–42.5</td><td>45.4</td><td>91.8</td></tr></tbody></table>
<table><caption>Table 1. *Cont.*</caption><thead><tr><th rowspan="2">Study</th><th rowspan="2">Country</th><th rowspan="2">GDP per Capital</th><th rowspan="2">Period of Data Collection</th><th colspan="4">Physicians</th><th colspan="2">Prevalence (%) of</th><th colspan="2">Smokers</th><th rowspan="2">% Men among Smokers</th></tr><tr><th>n</th><th>% Men</th><th>Age</th><th>Speciality</th><th>Regular Smokers</th><th>Occasional Smokers</th><th>Former Smokers</th><th>Total (Regular & Occasional)</th></tr></thead><tbody><tr><td>Braun 2004</td><td>USA</td><td>38,166</td><td>2002</td><td>1067</td><td>68</td><td>46</td><td>Not defined</td><td></td><td></td><td>18.6</td><td>1.3</td><td></td></tr><tr><td>Brenner 1996</td><td>Germany</td><td>26,334</td><td>1992–1993</td><td>696</td><td>52.6</td><td></td><td>Study</td><td></td><td></td><td>11.9</td><td>23.7</td><td>64.8</td></tr><tr><td>Brink 1994</td><td>USA</td><td>23,954</td><td>1990</td><td>132</td><td></td><td></td><td>Not defined</td><td></td><td></td><td></td><td>1.6</td><td></td></tr><tr><td>Brotons 2005</td><td>Croatia, Estonia, Georgia, Greece, Ireland, Malta, Poland, Slovakia, Slovenia, Spain, Sweden</td><td></td><td>2000</td><td>2082</td><td>40</td><td>35.6–51.4</td><td>Family medicine</td><td></td><td></td><td></td><td>16.4</td><td></td></tr><tr><td>Burgess 1970</td><td>USA</td><td></td><td>1963–1968</td><td>1863</td><td></td><td></td><td>Not defined</td><td></td><td></td><td></td><td>27.3</td><td></td></tr><tr><td>Burgess 1978</td><td>USA</td><td>6741</td><td>1973</td><td>1234</td><td>95.1</td><td></td><td>Family medicine, Internal medicine, Paediatry, Psychiatry, Radiology, Pathology, Gynecology, Orthopaedy, Anesthesiology-Reanimation, Ear Nose Throat, Others</td><td></td><td></td><td>35.4</td><td>19</td><td>95.7</td></tr><tr><td>Cao 2011</td><td>USA</td><td></td><td></td><td>19,705</td><td>100</td><td>58.3</td><td>Not defined</td><td></td><td></td><td>41.7</td><td>6.7</td><td>100</td></tr><tr><td>Carlos 2020</td><td>Spain</td><td>30,389</td><td>2018</td><td>890</td><td>52</td><td>51.7</td><td>Not defined</td><td></td><td></td><td>24</td><td>16.5</td><td></td></tr><tr><td>Ceraso 2009</td><td>China</td><td>2099</td><td>2006</td><td>103</td><td>100</td><td></td><td>Not defined</td><td></td><td></td><td></td><td>49.5</td><td>100</td></tr><tr><td>Chaudhry 2009</td><td>Pakistan</td><td>874</td><td>2006</td><td>120</td><td>75</td><td></td><td>Not defined</td><td></td><td></td><td></td><td>23.8</td><td>100</td></tr><tr><td>Cheng 1990</td><td>Hong Kong</td><td>9071</td><td>1987</td><td>133</td><td>81.2</td><td>25</td><td>Not defined</td><td>33.3</td><td>66.7</td><td></td><td>15.8</td><td>90.5</td></tr></tbody></table>
<table><caption>Table 1. *Cont.*</caption><thead><tr><th rowspan="2">Study</th><th rowspan="2">Country</th><th rowspan="2">GDP per Capital</th><th rowspan="2">Period of Data Collection</th><th colspan="4">Physicians</th><th colspan="2">Prevalence (%) of Smokers</th><th colspan="2">Smokers</th><th rowspan="2">% Men among Smokers</th></tr><tr><th>n</th><th>% Men</th><th>Age</th><th>Speciality</th><th>Regular Smokers</th><th>Occasional Smokers</th><th>Former Smokers</th><th>Total (Regular & Occasional)</th></tr></thead><tbody><tr><td>Coe 1971</td><td>USA</td><td>862</td><td>1967</td><td>1572</td><td></td><td></td><td>Family medicine, Internal medicine</td><td></td><td></td><td>31.3-34.9</td><td>29.6</td><td></td></tr><tr><td>Cofta 2008</td><td>Poland</td><td>14,001</td><td></td><td>117</td><td></td><td></td><td>Not defined</td><td>81.8</td><td>18.2</td><td>10.3</td><td>9.4</td><td></td></tr><tr><td>Das 2013</td><td>India</td><td>1462</td><td>2011</td><td>600</td><td>67</td><td></td><td>Study</td><td></td><td></td><td></td><td>14.5</td><td></td></tr><tr><td>Davies 1989</td><td>UK</td><td>13,119</td><td>1987</td><td>94</td><td>83</td><td></td><td>Not defined</td><td></td><td></td><td>26</td><td>3</td><td></td></tr><tr><td>De Col 2010</td><td>France</td><td>45,334</td><td>2008-2009</td><td>332</td><td>67.8</td><td>50.7</td><td>Family medicine</td><td>57.4</td><td>42.6</td><td>34</td><td>18.4</td><td></td></tr><tr><td>Dekker 1993</td><td>Netherlands</td><td>17,176</td><td>1989</td><td>619</td><td>70.6</td><td></td><td>Family medicine, Study, Others</td><td></td><td></td><td>29.6</td><td>83.6</td><td></td></tr><tr><td>De Oliveira 2013</td><td>USA</td><td>52,782</td><td></td><td>1480</td><td></td><td></td><td>Study</td><td></td><td></td><td></td><td>6.9</td><td></td></tr><tr><td>Desalu 2009</td><td>Nigeria</td><td>1384</td><td>2008</td><td>436</td><td>75.7</td><td>30.6</td><td>Not defined</td><td></td><td></td><td></td><td>17.7</td><td></td></tr><tr><td>Djalalinia 2011</td><td>Iran</td><td>1892</td><td>2002-2003</td><td>5140</td><td>74</td><td>35</td><td>Family medicine</td><td></td><td></td><td></td><td>11.8</td><td>100</td></tr><tr><td>Dodds 1979</td><td>Australia</td><td>7763</td><td>1977</td><td>275</td><td>84.7</td><td></td><td>Not defined</td><td></td><td></td><td>30</td><td>21</td><td>87.9</td></tr><tr><td>Doll 1954</td><td>UK</td><td></td><td>1951</td><td>24,389</td><td>100</td><td></td><td>Not defined</td><td></td><td></td><td></td><td>87.3</td><td>100</td></tr><tr><td>Doll 1964</td><td>UK</td><td></td><td>1951-1958</td><td>31,208</td><td>100</td><td></td><td>Not defined</td><td></td><td></td><td>15.3-26.6</td><td>61.8</td><td>100</td></tr><tr><td>Doll 1994</td><td>UK</td><td></td><td>1951-1990</td><td>10,812</td><td>100</td><td></td><td>Not defined</td><td></td><td></td><td>13-60</td><td>39.9</td><td>100</td></tr><tr><td>Doll 2004</td><td>UK</td><td>19,709</td><td>1978</td><td>12,669</td><td>100</td><td></td><td>Not defined</td><td></td><td></td><td>46.3</td><td>30.5</td><td>100</td></tr><tr><td>Easton 2001</td><td>USA</td><td>26,464</td><td>1993-1994</td><td>1590</td><td>0</td><td>41</td><td>Not defined</td><td></td><td></td><td>19.9</td><td>3.5</td><td>0</td></tr><tr><td>Easton 2001</td><td>USA</td><td>26,464</td><td>1994</td><td>1397</td><td>0</td><td>42</td><td>Not defined</td><td></td><td></td><td>21.5</td><td>4.7</td><td>0</td></tr><tr><td>Edwards 2008</td><td>New Zealand</td><td>26,671</td><td>2006</td><td>10,200</td><td>60.2</td><td></td><td>Family medicine, Study, Radiology, Gynecology, Anesthesiology-Reanimation, Others</td><td></td><td></td><td></td><td>3.5</td><td>67.6</td></tr></tbody></table>
<table><caption>Table 1. *Cont.*</caption><thead><tr><th rowspan="2">Study</th><th rowspan="2">Country</th><th rowspan="2">GDP per Capital</th><th rowspan="2">Period of Data Collection</th><th colspan="4">Physicians</th><th colspan="2">Prevalence (%) of</th><th colspan="2">Smokers</th><th rowspan="2">% Men among Smokers</th></tr><tr><th>n</th><th>% Men</th><th>Age</th><th>Speciality</th><th>Regular Smokers</th><th>Occasional Smokers</th><th>Former Smokers</th><th>Total (Regular & Occasional)</th></tr></thead><tbody><tr><td>Edwards 2018</td><td>New Zealand</td><td>42,949</td><td>2013</td><td>12,684</td><td>55.7</td><td></td><td>Family medicine, Study, Radiology, Gynecology, Anesthesiology-Reanimation, Others</td><td></td><td></td><td>12.1</td><td>2.1</td><td>61.6</td></tr><tr><td>Fadhil 2007</td><td>Bahrain</td><td>17,959</td><td>2005</td><td>120</td><td>35.8</td><td>36.5</td><td>Family medicine</td><td></td><td></td><td>10</td><td>24.2</td><td></td></tr><tr><td>Fanello 1990</td><td>France</td><td></td><td>1973–1987</td><td>2718</td><td></td><td></td><td>Family medicine</td><td></td><td></td><td></td><td>44.6</td><td></td></tr><tr><td>Fathi 2016</td><td>Iran</td><td>7833</td><td>2012–2013</td><td>225</td><td></td><td></td><td>Not defined</td><td></td><td></td><td></td><td>21.3</td><td></td></tr><tr><td>Fowler 1989</td><td>UK</td><td>15,987</td><td>1988</td><td>3240</td><td>77</td><td></td><td>Family medicine</td><td></td><td></td><td>33</td><td>13.5</td><td></td></tr><tr><td>Franceschi 1986</td><td>Italy</td><td>7964</td><td>1985</td><td>709</td><td></td><td></td><td>Family medicine, Internal medicine, Public health, Others</td><td></td><td></td><td>14–26</td><td>31.3</td><td></td></tr><tr><td>Frank 1998</td><td>USA</td><td>27,777</td><td>1994</td><td>4501</td><td>0</td><td>42.2</td><td>Not defined</td><td></td><td></td><td>18.6</td><td>3.7</td><td>0</td></tr><tr><td>Frank 2009</td><td>Canada</td><td>44,545</td><td>2007–2008</td><td>3213</td><td>66</td><td></td><td>Not defined</td><td>57.1</td><td>42.9</td><td></td><td>14</td><td></td></tr><tr><td>Freour 2011</td><td>France</td><td>41,575</td><td>2009</td><td>337</td><td></td><td></td><td>Not defined</td><td></td><td></td><td>30.6</td><td>12.5</td><td></td></tr><tr><td>Garfinkel 1976</td><td>USA</td><td></td><td>1959–1972</td><td>8503</td><td></td><td></td><td>Not defined</td><td></td><td></td><td></td><td>32.7</td><td></td></tr><tr><td>Glavas 2003</td><td>Greece</td><td>18,478</td><td></td><td>119</td><td>76.5</td><td></td><td>Not defined</td><td></td><td></td><td></td><td>37</td><td></td></tr><tr><td>Grossman 1999</td><td>Costa Rica</td><td>2828</td><td>1993–1994</td><td>216</td><td>70.8</td><td>41</td><td>Not defined</td><td></td><td></td><td>40</td><td>19.4</td><td>61.9</td></tr><tr><td>Gunes 2005</td><td>Turkey</td><td>3660</td><td>2002</td><td>257</td><td>77.8</td><td>31.3</td><td>Not defined</td><td>81.3</td><td>18.8</td><td></td><td>37.4</td><td></td></tr><tr><td>Gupta 2013</td><td>USA</td><td>47,100</td><td>2009</td><td>177</td><td>41.2</td><td></td><td>Internal medicine, Paediatry, Others, Emergency</td><td>99.6</td><td>0.4</td><td></td><td>0.6</td><td></td></tr><tr><td>Hallett 1983</td><td>UK</td><td></td><td>1980</td><td>385</td><td></td><td></td><td>Family medicine</td><td></td><td></td><td>44.4</td><td>27.8</td><td></td></tr></tbody></table>
<table><caption>Table 1. *Cont.*</caption><thead><tr><th rowspan="2">Study</th><th rowspan="2">Country</th><th rowspan="2">GDP per Capital</th><th rowspan="2">Period of Data Collection</th><th colspan="4">Physicians</th><th colspan="2">Prevalence (%) of Smokers</th><th colspan="2">Total (Regular & Occasional)</th><th rowspan="2">% Men among Smokers</th></tr><tr><th>n</th><th>% Men</th><th>Age</th><th>Speciality</th><th>Regular Smokers</th><th>Occasional Smokers</th><th>Former Smokers</th><th>Total (Regular & Occasional)</th></tr></thead><tbody><tr><td>Hamadeh 1999</td><td>Bahrain</td><td>10,131</td><td>1994</td><td>122</td><td>52.5</td><td></td><td>Family medicine</td><td>66.7</td><td>33.3</td><td>14.8</td><td>17.2</td><td>81</td></tr><tr><td>Han Zao Li 2008</td><td>China</td><td>1753</td><td>2005</td><td>326</td><td>59.2</td><td></td><td>Not defined</td><td></td><td></td><td></td><td>42</td><td>81.8</td></tr><tr><td>Hay 1976</td><td>New Zealand</td><td>1963–1972</td><td></td><td>763</td><td>0</td><td>45</td><td>Family medicine, Psychiatry, Anesthesiology-Reanimation, Others</td><td>93.6</td><td>6.3</td><td>22.3–26.9</td><td>20.4</td><td></td></tr><tr><td>Hay 1998</td><td>New Zealand</td><td>1976–1996</td><td></td><td>7335</td><td>68.5</td><td></td><td>Family medicine, Radiology, Gynecology, Anesthesiology-Reanimation, Others</td><td></td><td></td><td></td><td>5</td><td>71.5</td></tr><tr><td>Heloma 1998</td><td>Finland</td><td>26,009</td><td></td><td>332</td><td>84.3</td><td>42.6</td><td>Not defined</td><td>40</td><td>60</td><td>20.2</td><td>24.1</td><td></td></tr><tr><td>Hensrud 1993</td><td>USA</td><td>26,387</td><td></td><td>389</td><td></td><td></td><td>Not defined</td><td></td><td></td><td>37.3</td><td>9</td><td>97.1</td></tr><tr><td>Hepburn 2000</td><td>USA</td><td>31,573</td><td>1997</td><td>150</td><td></td><td></td><td>Family medicine</td><td></td><td></td><td></td><td>11</td><td></td></tr><tr><td>Heponiemi 2008</td><td>Finland</td><td>41,188</td><td>2006</td><td>2652</td><td>40.8</td><td>53</td><td>Not defined</td><td></td><td></td><td></td><td>12.4</td><td></td></tr><tr><td>Hidalgo 2016</td><td>Brazil</td><td>13,246</td><td>2011</td><td>182</td><td>56.6</td><td></td><td>Not defined</td><td></td><td></td><td>12.3</td><td>5.5</td><td></td></tr><tr><td>Hill 1997</td><td>USA</td><td>27,777</td><td>1994</td><td>121</td><td>53.7</td><td></td><td>Not defined</td><td></td><td></td><td></td><td>4.1</td><td></td></tr><tr><td>Hodgetts 2004</td><td>Bosnia Herzegovina</td><td>1769</td><td>2002</td><td>112</td><td></td><td></td><td>Not defined</td><td></td><td></td><td>13.6</td><td>39.3</td><td></td></tr></tbody></table>
<table><caption>Table 1. *Cont.*</caption><thead><tr><th rowspan="2">Study</th><th rowspan="2">Country</th><th rowspan="2">GDP per Capital</th><th rowspan="2">Period of Data Collection</th><th colspan="4">Physicians</th><th colspan="2">Prevalence (%) of Smokers</th><th colspan="2">Smokers</th><th rowspan="2">% Men among Smokers</th></tr><tr><th>n</th><th>% Men</th><th>Age</th><th>Speciality</th><th>Regular Smokers</th><th>Occasional Smokers</th><th>Former Smokers</th><th>Total (Regular & Occasional)</th></tr></thead><tbody><tr><td>Hoseainrezae 2013</td><td>Iran</td><td>6111</td><td></td><td>252</td><td></td><td></td><td>Not defined</td><td></td><td>7.1</td><td>9.5</td><td></td></tr><tr><td>Huang 2013</td><td>China</td><td>5618</td><td>2011</td><td>720</td><td>100</td><td></td><td>Not defined</td><td>60</td><td>40</td><td>25.7</td><td>100</td></tr><tr><td>Hughes 1991</td><td>USA</td><td>20,039</td><td>1987</td><td>1733</td><td>69.4</td><td>30</td><td>Not defined</td><td></td><td></td><td>5.3</td><td></td></tr><tr><td>Hughes 1992</td><td>USA</td><td>22,857</td><td>1989–1990</td><td>5426</td><td>82.4</td><td></td><td>Not defined</td><td></td><td></td><td>3.9</td><td></td></tr><tr><td>Hughes 1999</td><td>USA</td><td>22,857</td><td>1989–1990</td><td>5418</td><td></td><td></td><td>Family medicine, Internal medicine, Emergency, Pathology, Paediatry, Psychiatry, Anesthesiology-Reanimation, Gynecology, Others</td><td></td><td></td><td>14.3</td><td></td></tr><tr><td>Hung 2013</td><td>USA</td><td>48,467</td><td>2010</td><td>1000</td><td>68.5</td><td>45.3</td><td>Family medicine</td><td></td><td></td><td>4</td><td></td></tr><tr><td>Hussain 1993</td><td>UK</td><td>19,901</td><td>1991</td><td>1069</td><td></td><td></td><td>Not defined</td><td></td><td></td><td>5</td><td></td></tr><tr><td>Içli 1992</td><td>Turkey</td><td>2736</td><td>1991</td><td>200</td><td></td><td></td><td>Study</td><td></td><td></td><td>34</td><td></td></tr><tr><td>Innos 2002</td><td>Estonia</td><td></td><td>1982</td><td>3673</td><td>23.7</td><td></td><td>Not defined</td><td></td><td>13.1</td><td>21.3</td><td>45.6</td></tr><tr><td>Jacot Sadowski 2009</td><td>Swiss</td><td>41,376</td><td>2002</td><td>1856</td><td>78.8</td><td></td><td>Not defined</td><td>40.8</td><td>59.2</td><td>17.6</td><td></td></tr><tr><td>Jiang 2007</td><td>China</td><td>1509</td><td>2004</td><td>3552</td><td>55.1</td><td></td><td>Not defined</td><td></td><td>2.7</td><td>22.9</td><td>98</td></tr><tr><td>Jiménez-Ruiz 2015</td><td>Spain</td><td>29,462</td><td>2014</td><td>416</td><td>59.4</td><td></td><td>Not defined</td><td>80.4</td><td>19.6</td><td>11.1</td><td></td></tr><tr><td>Jingi 2015</td><td>Cameroon</td><td>1381</td><td>2012</td><td>65</td><td>69.2</td><td>39.1</td><td>Family medicine</td><td></td><td></td><td>12.3</td><td>100</td></tr></tbody></table>
<table><caption>Table 1. *Cont.*</caption><thead><tr><th rowspan="2">Study</th><th rowspan="2">Country</th><th rowspan="2">GDP per Capital</th><th rowspan="2">Period of Data Collection</th><th colspan="4">Physicians</th><th colspan="2">Prevalence (%) of</th><th colspan="2">Smokers</th><th rowspan="2">% Men among Smokers</th></tr><tr><th>n</th><th>% Men</th><th>Age</th><th>Speciality</th><th>Regular Smokers</th><th>Occasional Smokers</th><th>Former Smokers</th><th>Total (Regular & Occasional)</th></tr></thead><tbody><tr><td>John 2003</td><td>Germany</td><td></td><td>1989–1999</td><td>2509</td><td></td><td></td><td>Not defined</td><td></td><td>18.9–22.5</td><td>20.4</td><td></td></tr><tr><td>Joossens 1987</td><td>Belgium</td><td>8846</td><td>1983</td><td>2157</td><td></td><td></td><td>Not defined</td><td></td><td>33</td><td>32</td><td></td></tr><tr><td>Josseran 2000</td><td>France, Netherlands, Spain, UK, Greece, Brazil</td><td></td><td>1992–1997</td><td>16,788</td><td></td><td></td><td>Family medicine, Study, Others</td><td></td><td></td><td>9.5</td><td></td></tr><tr><td>Josseran 2005</td><td>France</td><td>24,974</td><td>1998</td><td>2073</td><td>79.3</td><td>45.1</td><td>Family medicine</td><td></td><td>45.5</td><td>32.1</td><td>83.6</td></tr><tr><td>Julião 2013</td><td>Brazil</td><td>8598</td><td>2009</td><td>515</td><td>66.8</td><td>45.3</td><td>Not defined</td><td></td><td>23.3</td><td>5.8</td><td></td></tr><tr><td>Kaetsu 2002</td><td>Japan</td><td></td><td>1983–1990</td><td>5312</td><td>95.7</td><td></td><td>Not defined</td><td></td><td></td><td>36.6</td><td>99.3</td></tr><tr><td>Kaetsu 2002</td><td>Japan</td><td>10,425</td><td>1983</td><td>4190</td><td>95.6</td><td></td><td>Not defined</td><td></td><td></td><td>41.9</td><td>99</td></tr><tr><td>Kai 2008</td><td>Japan</td><td>37,217</td><td>2005</td><td>1063</td><td></td><td></td><td>Anesthesiology-Reanimation, Chest surgery</td><td></td><td>30</td><td>12</td><td></td></tr><tr><td>Kaneita 2010</td><td>Japan</td><td></td><td>2000–2008</td><td>10,890</td><td>66.4</td><td></td><td>Not defined</td><td></td><td></td><td>16.1</td><td>88.2</td></tr><tr><td>Kawahara 2000</td><td>Japan</td><td>38,437</td><td>1996–1997</td><td>709</td><td>91.8</td><td>54.7</td><td>Not defined</td><td></td><td>46.3</td><td>26</td><td>98.4</td></tr><tr><td>Kawakami 1997</td><td>Japan</td><td>39,269</td><td>1994</td><td>323</td><td>84.8</td><td>59.8</td><td>Not defined</td><td></td><td>46.1</td><td>21.1</td><td>95.6</td></tr><tr><td>Kawane 1993</td><td>Japan</td><td>24,813</td><td>1989</td><td>6224</td><td></td><td></td><td>Pneumology</td><td></td><td>39.4</td><td>24.8</td><td></td></tr><tr><td>Kono 1985</td><td>Japan</td><td>920</td><td>1965</td><td>5446</td><td>100</td><td></td><td>Not defined</td><td></td><td></td><td>67.8</td><td></td></tr><tr><td>Kotz 2007</td><td>Netherlands</td><td>29,204</td><td>2002–2003</td><td>1180</td><td></td><td>45.9–48.3</td><td>Family medicine, Cardiology, Pneumology</td><td></td><td>24.8–29.7</td><td>6.6</td><td></td></tr></tbody></table>
<table><caption>Table 1. *Cont.*</caption><thead><tr><th rowspan="2">Study</th><th rowspan="2">Country</th><th rowspan="2">GDP per Capital</th><th rowspan="2">Period of Data Collection</th><th colspan="4">Physicians</th><th colspan="2">Prevalence (%) of Smokers</th><th colspan="2">Smokers</th><th rowspan="2">% Men among Smokers</th></tr><tr><th>n</th><th>% Men</th><th>Age</th><th>Speciality</th><th>Regular Smokers</th><th>Occasional Smokers</th><th>Former Smokers</th><th>Total (Regular & Occasional)</th></tr></thead><tbody><tr><td>Lam 2011</td><td>China</td><td>2099</td><td>2006</td><td>504</td><td>100</td><td></td><td>Not defined</td><td></td><td></td><td>46.2</td><td>100</td></tr><tr><td>La Vecchia 2000</td><td>Italy</td><td>21,998</td><td>1999</td><td>501</td><td>76.6</td><td>45</td><td>Not defined</td><td>87.7</td><td>12.3</td><td>26.5</td><td>27.5</td></tr><tr><td>Lefcoe 1970</td><td>UK</td><td>2348</td><td></td><td>310</td><td>100</td><td>45.7</td><td>Not defined</td><td></td><td></td><td>19.7</td><td>51.9</td><td>100</td></tr><tr><td>Legnini 1987</td><td>USA</td><td>18,237</td><td>1985</td><td>266</td><td></td><td></td><td>Public health, Internal medicine, Psychiatry, Others</td><td></td><td></td><td>17.1–37</td><td>21.1</td></tr><tr><td>Lindfors 2009</td><td>Finland</td><td>37,703</td><td>2004</td><td>328</td><td>53.4</td><td>47</td><td>Anesthesiology-Reanimation</td><td></td><td></td><td></td><td>16.5</td></tr><tr><td>Linn 1986</td><td>USA</td><td>17,134</td><td>1984</td><td>211</td><td>91</td><td></td><td>Not defined</td><td></td><td></td><td></td><td>4</td></tr><tr><td>Lipp 1972</td><td>USA</td><td>5234</td><td>1970</td><td>1061</td><td></td><td></td><td>Study</td><td></td><td></td><td></td><td>17</td></tr><tr><td>Lipp 1972</td><td>USA</td><td>5609</td><td>1971</td><td>1314</td><td></td><td></td><td>Not defined</td><td></td><td></td><td>40</td><td>21</td></tr><tr><td>Magee 2017</td><td>Georgia</td><td>4739</td><td>2014</td><td>86</td><td></td><td></td><td>Not defined</td><td></td><td></td><td>14</td><td>18.6</td></tr><tr><td>Malik 2010</td><td>Pakistan</td><td>1007</td><td>2009</td><td>234</td><td>69.7</td><td></td><td>Not defined</td><td></td><td></td><td></td><td>37.2</td><td>94.3</td></tr><tr><td>Manson 2000</td><td>USA</td><td>14,434</td><td>1982</td><td>21,068</td><td>100</td><td></td><td>Not defined</td><td></td><td></td><td>39.2</td><td>11</td><td>100</td></tr><tr><td>Mappin-Kasirer 2020</td><td>UK</td><td></td><td>1951–2016</td><td>29,737</td><td>100</td><td></td><td>Not defined</td><td></td><td></td><td>14.9–68.4</td><td>8.4–67.2</td><td>100</td></tr><tr><td>Marakoğlu 2006</td><td>Turkey</td><td>8035</td><td></td><td>363</td><td>69.1</td><td>34.2</td><td>Not defined</td><td></td><td></td><td>9.9</td><td>28.7</td><td>85.6</td></tr><tr><td>Márk 1998</td><td>Hungary</td><td>4495</td><td>1995</td><td>170</td><td>62.9</td><td></td><td>Not defined</td><td></td><td></td><td></td><td>25.9</td></tr><tr><td>Mathavan 2009</td><td>India</td><td>1102</td><td></td><td>1433</td><td>65.7</td><td></td><td>Not defined</td><td>66.5</td><td>33.5</td><td></td><td>11.9</td><td>100</td></tr><tr><td>McAuliffe 1984</td><td>USA</td><td>14,439</td><td>1982</td><td>134</td><td></td><td></td><td>Not defined</td><td></td><td></td><td></td><td>6</td></tr></tbody></table>
<table><caption>Table 1. *Cont.*</caption><thead><tr><th rowspan="2">Study</th><th rowspan="2">Country</th><th rowspan="2">GDP per Capital</th><th rowspan="2">Period of Data Collection</th><th colspan="4">Physicians</th><th colspan="2">Prevalence (%) of</th><th colspan="2">Smokers</th><th rowspan="2">% Men among Smokers</th></tr><tr><th>n</th><th>% Men</th><th>Age</th><th>Speciality</th><th>Regular Smokers</th><th>Occasional Smokers</th><th>Former Smokers</th><th>Total (Regular & Occasional)</th></tr></thead><tbody><tr><td>McEwen 2001</td><td>UK</td><td>28,383</td><td>1999</td><td>303</td><td>68</td><td></td><td>Family medicine</td><td></td><td></td><td></td><td>4</td><td></td></tr><tr><td>McGrady 2007</td><td>Ireland</td><td>47,631</td><td>2004</td><td>650</td><td>46.1</td><td></td><td>Family medicine</td><td></td><td></td><td>15.2</td><td>4.2</td><td></td></tr><tr><td>Mejia 2011</td><td>Argentina</td><td>5110</td><td>2005</td><td>235</td><td>54.5</td><td>45</td><td>Gynecology</td><td></td><td></td><td>26.3</td><td>35.3</td><td></td></tr><tr><td>Merrill 2006</td><td>Jordan</td><td>2548</td><td>2006</td><td>251</td><td>69.3</td><td>45.3</td><td>Not defined</td><td>63</td><td>37</td><td>17.5</td><td>18.3</td><td>84.8</td></tr><tr><td>Meshefedjian 2010</td><td>Canada</td><td></td><td>2000–2004</td><td>610</td><td>55.1</td><td></td><td>Family medicine</td><td></td><td></td><td>32</td><td>7.4</td><td>51.1</td></tr><tr><td>Mikalauskas 2012</td><td>Lithuania</td><td>11,837</td><td>2009</td><td>59</td><td></td><td>43.8–44.4</td><td>Anesthesiology-Reanimation, Others</td><td></td><td></td><td></td><td>13.6</td><td></td></tr><tr><td>Misra 2004</td><td>USA</td><td>32,854</td><td>1998–2000</td><td>254</td><td></td><td>50.88</td><td>Not defined</td><td></td><td></td><td></td><td>3.5</td><td></td></tr><tr><td>Miwa 1995</td><td>Japan</td><td>31,465</td><td>1992</td><td>17</td><td>94.1</td><td></td><td>Cardiology</td><td></td><td></td><td></td><td>41.2</td><td></td></tr><tr><td>Mohan 2006</td><td>India</td><td>547</td><td>2003</td><td>229</td><td>66.4</td><td>42.7</td><td>Not defined</td><td></td><td></td><td>14.4</td><td>8.7</td><td>100</td></tr><tr><td>Mohseni-Bandpei 2011</td><td>Iran</td><td>5630</td><td>2008</td><td>223</td><td>48.4</td><td>42.7</td><td>Not defined</td><td></td><td></td><td></td><td>13.5</td><td></td></tr><tr><td>Moreno 2006</td><td>Spain</td><td>21,463</td><td>2003</td><td>147</td><td></td><td>21.5–39.1</td><td>Study, Others</td><td></td><td></td><td>7.3–26.7</td><td>47.6</td><td></td></tr><tr><td>Mostafa 2017</td><td>Egypt</td><td>3525</td><td>2016</td><td>521</td><td>64.3</td><td></td><td>Internal medicine, Dermatology, Paediatry, Gynecology, Others</td><td></td><td></td><td>8.3</td><td>21.5</td><td>89.3</td></tr><tr><td>Movsisyan 2019</td><td>Armenia</td><td>3607</td><td>2015</td><td>36</td><td>25</td><td></td><td>Study</td><td></td><td></td><td>0</td><td>16.7</td><td>100</td></tr></tbody></table>
<table><caption>Table 1. *Cont.*</caption><thead><tr><th rowspan="2">Study</th><th rowspan="2">Country</th><th rowspan="2">GDP per Capital</th><th rowspan="2">Period of Data Collection</th><th colspan="4">Physicians</th><th colspan="2">Prevalence (%) of Smokers</th><th colspan="2">Smokers</th><th rowspan="2">% Men among Smokers</th></tr><tr><th>n</th><th>% Men</th><th>Age</th><th>Speciality</th><th>Regular Smokers</th><th>Occasional Smokers</th><th>Former Smokers</th><th>Total (Regular & Occasional)</th></tr></thead><tbody><tr><td>Mubeen 2008</td><td>Pakistan</td><td>683</td><td>2005</td><td>165</td><td>43.6</td><td>20.16-22.89</td><td>Study</td><td>37.5</td><td>62.5</td><td>2.4-3.8</td><td>14.5</td><td>95.8</td></tr><tr><td>Naji 2006</td><td>Ireland</td><td>32,541</td><td>2002</td><td>106</td><td>61.3</td><td></td><td>Not defined</td><td></td><td></td><td>22.6</td><td>21.7</td><td>60.9</td></tr><tr><td>Nakládalová 2005</td><td>Czech Republic</td><td>8033</td><td>2002-2004</td><td>370</td><td>54.9</td><td></td><td>Not defined</td><td></td><td></td><td></td><td>16.8</td><td>62.9</td></tr><tr><td>Nardini 1998</td><td>Italy</td><td>20,665</td><td>1995</td><td>605</td><td>81.3</td><td>44</td><td>Not defined</td><td></td><td></td><td>34.4</td><td>25</td><td></td></tr><tr><td>Nawaz 2007</td><td>Pakistan</td><td>625</td><td>2004-2005</td><td>1029</td><td>44.6</td><td>21</td><td>Study</td><td>63.5</td><td>36.5</td><td>22.4</td><td>11.2</td><td>89.6</td></tr><tr><td>Nawaz 2008</td><td>Pakistan</td><td>837</td><td>2006-2007</td><td>227</td><td></td><td></td><td>Family medicine</td><td></td><td></td><td></td><td>36.1</td><td></td></tr><tr><td>Ndiaye 2001</td><td>Senegal</td><td>681</td><td>1999</td><td>163</td><td>78.5</td><td>41</td><td>Not defined</td><td></td><td></td><td>6.8</td><td>27.6</td><td>93.3</td></tr><tr><td>Nelson 1994</td><td>USA</td><td></td><td>1974-1991</td><td>379</td><td></td><td></td><td>Not defined</td><td></td><td></td><td>27.8-32</td><td>9</td><td></td></tr><tr><td>Ng 2007</td><td>Indonesia</td><td>1065</td><td>2003</td><td>447</td><td></td><td></td><td>Not defined</td><td></td><td></td><td></td><td>11.6</td><td>96.2</td></tr><tr><td>Nollen 2004</td><td>Nigeria</td><td>742</td><td>2002</td><td>373</td><td>83.9</td><td>33</td><td>Not defined</td><td></td><td></td><td></td><td>2.9</td><td></td></tr><tr><td>Nutbeam 1990</td><td>UK</td><td>19,096</td><td></td><td>304</td><td>82.6</td><td></td><td>Family medicine</td><td></td><td></td><td>32</td><td>13.8</td><td>100</td></tr><tr><td>Obeidat 2017</td><td>Jordan</td><td>4073</td><td>2014</td><td>104</td><td></td><td>42.7</td><td>Not defined</td><td></td><td></td><td></td><td>44.2</td><td></td></tr><tr><td>O'Cathail 2013</td><td>Ireland</td><td>52,105</td><td>2009-2010</td><td>248</td><td></td><td></td><td>Not defined</td><td></td><td></td><td>20.8-22</td><td>8.1</td><td>50</td></tr><tr><td>Ohida 2001</td><td>Japan</td><td>38,532</td><td>2000</td><td>3771</td><td>66.3</td><td></td><td>Not defined</td><td></td><td></td><td></td><td>20.3</td><td>88.7</td></tr></tbody></table>
<table><caption>Table 1. *Cont.*</caption><thead><tr><th rowspan="2">Study</th><th rowspan="2">Country</th><th rowspan="2">GDP per Capital</th><th rowspan="2">Period of Data Collection</th><th colspan="5">Physicians</th><th colspan="2">Prevalence (%) of Smokers</th><th rowspan="2">Total (Regular & Occasional)</th><th rowspan="2">% Men among Smokers</th></tr><tr><th>n</th><th>% Men</th><th>Age</th><th>Speciality</th><th>Regular Smokers</th><th>Occasional Smokers</th><th>Former Smokers</th></tr></thead><tbody><tr><td>O'Keeffe 2019</td><td>Ireland</td><td>55,413</td><td>2014</td><td>1746</td><td>50.5</td><td></td><td>Paediatry, Pathology, Psychiatry, Emergency, Anesthesiology-Reanimation, Gynecology, Ophtalmology, Others</td><td>27.2</td><td>72.8</td><td>9.3</td><td>61.1</td></tr><tr><td>Öztürk 2012</td><td>Turkey</td><td>11,707</td><td></td><td>80</td><td>88.8</td><td></td><td>Surgery, Study</td><td></td><td>10</td><td>17.5</td><td>100</td></tr><tr><td>Pärna 2005</td><td>Estonia, Finland</td><td></td><td>2001–2002</td><td>4549</td><td>29.9</td><td></td><td>Not defined</td><td>49.1</td><td>50.2</td><td>19.6–36.9</td><td>14.2</td><td>48.5</td></tr><tr><td>Pärna 2005</td><td>Estonia</td><td>5345</td><td>2002</td><td>2668</td><td>17.4</td><td>47.6</td><td>Not defined</td><td></td><td></td><td>19.6</td><td>13.3</td><td>32.8</td></tr><tr><td>Pärna 2017</td><td>Estonia</td><td></td><td>1982–2014</td><td>9423</td><td>20.2</td><td></td><td>Not defined</td><td>82.5</td><td>17.5</td><td>13–19.1</td><td>14.7</td><td>41</td></tr><tr><td>Perrin 2006</td><td>Armenia</td><td>1192</td><td>2004</td><td>236</td><td>43.6</td><td>43.5</td><td>Not defined</td><td>83.8</td><td>16.2</td><td>10.59</td><td>33.9</td><td>71.3</td></tr><tr><td>Peykari 2010</td><td>Iran</td><td>6603</td><td></td><td>5140</td><td>74</td><td>35</td><td>Family medicine</td><td>47.8</td><td>52.2</td><td>6.5</td><td>15.9</td><td></td></tr><tr><td>Phillips 1968</td><td>Canada</td><td>3463</td><td></td><td>1743</td><td></td><td></td><td>Not defined</td><td>77.2</td><td>22.8</td><td>27.2</td><td>45.8</td><td></td></tr><tr><td>Pillay 2020</td><td>India</td><td>2005</td><td>2018</td><td>692</td><td>70.4</td><td>39</td><td>Not defined</td><td></td><td></td><td>8.5</td><td>7.7</td><td></td></tr><tr><td>Pipe 2009</td><td>France, Germany, Greece, Italy, Netherlands, Poland, Spain, Sweden, Swiss, Turkey, UK, USA, Canada, Mexico, Japan, Korea</td><td></td><td>2006</td><td>2836</td><td>76</td><td>48</td><td>Family medicine, Internal medicine</td><td></td><td></td><td></td><td>42.3</td><td>78.1</td></tr><tr><td>Piryani 2004</td><td>Pakistan</td><td>461</td><td>1998</td><td>200</td><td>71</td><td></td><td>Not defined</td><td></td><td></td><td></td><td>32</td><td>93.8</td></tr></tbody></table>
<table><caption>Table 1. *Cont.*</caption><thead><tr><th rowspan="2">Study</th><th rowspan="2">Country</th><th rowspan="2">GDP per Capital</th><th rowspan="2">Period of Data Collection</th><th colspan="4">Physicians</th><th>Prevalence (%) of</th><th colspan="2">Smokers</th><th rowspan="2">% Men among Smokers</th></tr><tr><th>n</th><th>% Men</th><th>Age</th><th>Speciality</th><th>Regular Smokers</th><th>Occasional Smokers</th><th>Former Smokers</th><th>Total (Regular & Occasional)</th></tr></thead><tbody><tr><td>Pizzo 2003</td><td>Italy</td><td>20,088</td><td>2000</td><td>526</td><td></td><td></td><td>Family medicine</td><td></td><td></td><td></td><td>28.3</td></tr><tr><td>Poanta 2006</td><td>Romania</td><td>5829</td><td></td><td>112</td><td>35.7</td><td>39.5</td><td>Not defined</td><td></td><td></td><td></td><td>42</td><td>46.8</td></tr><tr><td>Pöld 2017</td><td>Estonia</td><td></td><td>2002–2014</td><td>4877</td><td>16.9</td><td></td><td>Not defined</td><td>67.5</td><td>32.5</td><td></td><td>10.4</td><td>34.3</td></tr><tr><td>Pöld 2020</td><td>Estonia</td><td>20,367</td><td>2014</td><td>2903</td><td></td><td>54.5</td><td>Not defined</td><td></td><td></td><td></td><td>5.9</td><td>63.7</td></tr><tr><td>Polyzos 1995</td><td>Greece</td><td>11,176</td><td>1992</td><td>148</td><td></td><td></td><td>Not defined</td><td></td><td></td><td></td><td>49.3</td><td></td></tr><tr><td>Power 1999</td><td>Ireland</td><td>26,284</td><td>1999</td><td>171</td><td></td><td></td><td>Family medicine</td><td></td><td></td><td></td><td>16.1</td><td></td></tr><tr><td>Ramachandran 2008</td><td>India</td><td>628</td><td>2004–2006</td><td>2499</td><td>75.2</td><td>39</td><td>Not defined</td><td></td><td></td><td></td><td>8</td><td>100</td></tr><tr><td>Ranchal 2018</td><td>Spain</td><td></td><td>1986–2016</td><td>938</td><td></td><td></td><td>Not defined</td><td></td><td>3.6–20.1</td><td></td><td>23.2</td><td></td></tr><tr><td>Rankin 1975</td><td>Australia</td><td>6993</td><td></td><td>1276</td><td>87.6</td><td></td><td>Not defined</td><td></td><td>38</td><td></td><td>14.2</td><td></td></tr><tr><td>Ravara 2014</td><td>Portugal</td><td>23,030</td><td>2009</td><td>608</td><td>37.3</td><td>39.1</td><td>Family medicine, Study, Others</td><td></td><td></td><td>17.3</td><td>20.9</td><td>52</td></tr><tr><td>Reile 2018</td><td>Estonia</td><td>20,367</td><td>2014</td><td>1759</td><td>82.4</td><td></td><td>Not defined</td><td></td><td></td><td></td><td>7.9</td><td>86.3</td></tr><tr><td>Roche 1995</td><td>Australia</td><td>20,320</td><td>1995</td><td>1365</td><td>53.1</td><td>29.8</td><td>Not defined</td><td></td><td></td><td></td><td>6</td><td>53.7</td></tr><tr><td>Roche 1996</td><td>Australia</td><td>21,861</td><td>1996</td><td>908</td><td>46.9</td><td>28.7</td><td>Family medicine</td><td></td><td>8.3</td><td></td><td>4</td><td></td></tr><tr><td>Rurik 2008</td><td>Hungary</td><td>10,286</td><td>2004</td><td>156</td><td>42.9</td><td></td><td>Family medicine, Others</td><td></td><td></td><td></td><td>8.3</td><td>23.1</td></tr><tr><td>Rurik 2014</td><td>Hungary</td><td>13,046</td><td>2009</td><td>208</td><td>39.9</td><td>55.2</td><td>Not defined</td><td></td><td></td><td></td><td>5.8</td><td>33.3</td></tr><tr><td>Saadat 2012</td><td>Scandinavia</td><td></td><td></td><td>58</td><td>53.4</td><td></td><td>Anesthesiology-Reanimation</td><td></td><td></td><td></td><td>12.1</td><td></td></tr><tr><td>Sachs 1983</td><td>USA</td><td>15,561</td><td>1983</td><td>567</td><td></td><td></td><td>Pneumology</td><td></td><td></td><td></td><td>12</td><td></td></tr><tr><td>Saeed 1991</td><td>Saudi Arabia</td><td>7839</td><td></td><td>698</td><td></td><td></td><td>not defined</td><td></td><td></td><td></td><td>34</td><td></td></tr><tr><td>Saeys 2014</td><td>Belgium</td><td>47,349</td><td>2011</td><td>626</td><td>57</td><td>45</td><td>Family medicine</td><td>50</td><td>50</td><td>14</td><td>8</td><td>72</td></tr></tbody></table>
<table><caption>Table 1. *Cont.*</caption><thead><tr><th rowspan="2">Study</th><th rowspan="2">Country</th><th rowspan="2">GDP per Capital</th><th rowspan="2">Period of Data Collection</th><th colspan="4">Physicians</th><th>Prevalence</th><th>(%) of</th><th colspan="2">Smokers</th><th rowspan="2">% Men among Smokers</th></tr><tr><th>n</th><th>% Men</th><th>Age</th><th>Speciality</th><th>Regular Smokers</th><th>Occasional Smokers</th><th>Former Smokers</th><th>Total (Regular & Occasional)</th></tr></thead><tbody><tr><td>Salgado 2014</td><td>Argentina</td><td>12,849</td><td>2011</td><td>1659</td><td>26.9</td><td></td><td>Study</td><td>68.7</td><td>31.3</td><td>51.72</td><td>27.3</td><td>28.7</td></tr><tr><td>Samuels 1997</td><td>Israel</td><td>19,653</td><td></td><td>260</td><td>74.2</td><td>41</td><td>Study, Paediatry, Radiology, Others</td><td></td><td></td><td>20</td><td>15.8</td><td></td></tr><tr><td>Schnoll 2006</td><td>Russia</td><td>6920</td><td></td><td>63</td><td>82.5</td><td>41.3</td><td>Oncology</td><td></td><td></td><td>50.8</td><td>27</td><td></td></tr><tr><td>Scott 1992</td><td>USA</td><td></td><td>1963–1988</td><td>8589</td><td></td><td></td><td>Not defined</td><td></td><td></td><td></td><td>13.4</td><td></td></tr><tr><td>Sebo 2007</td><td>Swiss, Finland, Bosnia and Herzegovina, USA</td><td></td><td>1989–2004</td><td>1784</td><td>83.6</td><td>51</td><td>Family medicine, Internal medicine, Paediatry, Cardiology, Others</td><td></td><td></td><td>22.4</td><td>12.3</td><td>85.5</td></tr><tr><td>Seiler 1983</td><td>UK</td><td>8692</td><td>1983</td><td>607</td><td></td><td></td><td>Family medicine</td><td></td><td></td><td></td><td>19</td><td></td></tr><tr><td>Senior 1982</td><td>Canada</td><td>12,440</td><td>1982</td><td>88</td><td></td><td></td><td>Not defined</td><td></td><td></td><td></td><td>19.3</td><td></td></tr><tr><td>Sharma 1988</td><td>India</td><td></td><td>1982–1987</td><td>127</td><td></td><td></td><td>Not defined</td><td></td><td></td><td></td><td>34.6</td><td></td></tr><tr><td>Shi 2010</td><td>China</td><td>3832</td><td>2009</td><td>467</td><td>54.8</td><td></td><td>Anesthesiopgy-Reanimation</td><td></td><td></td><td>10.9</td><td>10.1</td><td></td></tr><tr><td>Shin 2012</td><td>China</td><td>4550</td><td>2010</td><td>17</td><td>47.1</td><td>39.4</td><td>Not defined</td><td></td><td></td><td></td><td>29.4</td><td></td></tr><tr><td>Shishani 2008</td><td>Jordan</td><td>3386</td><td></td><td>87</td><td></td><td></td><td>Not defined</td><td></td><td></td><td></td><td>43.7</td><td></td></tr><tr><td>Shishani 2011</td><td>Jordan</td><td>2774</td><td>2007</td><td>242</td><td>86</td><td></td><td>Not defined</td><td></td><td></td><td>12.4</td><td>46.7</td><td></td></tr><tr><td>Shkedy 2013</td><td>Isreal</td><td>36,310</td><td></td><td>140</td><td></td><td></td><td>Internal medicine, Paediatry, Anesthesiology -Reanimation, Ear Nose Throat, Gynecology</td><td></td><td></td><td>10–27.3</td><td>15.7</td><td>45.5</td></tr></tbody></table>
<table><caption>Table 1. *Cont.*</caption><thead><tr><th rowspan="2">Study</th><th rowspan="2">Country</th><th rowspan="2">GDP per Capital</th><th rowspan="2">Period of Data Collection</th><th colspan="4">Physicians</th><th colspan="2">Prevalence (%) of Smokers</th><th colspan="2">Smokers</th><th rowspan="2">% Men among Smokers</th></tr><tr><th>n</th><th>% Men</th><th>Age</th><th>Speciality</th><th>Regular Smokers</th><th>Occasional Smokers</th><th>Former Smokers</th><th>Total (Regular & Occasional)</th></tr></thead><tbody><tr><td>Siddiqui 2001</td><td>Saudi Arabia</td><td>8685</td><td></td><td>20</td><td></td><td></td><td>Not defined</td><td></td><td>10</td><td></td><td>20</td><td></td></tr><tr><td>Singh 1981</td><td>India</td><td>186</td><td>1977–1978</td><td>861</td><td></td><td></td><td>Study, Others</td><td></td><td></td><td></td><td>27.5</td><td></td></tr><tr><td>Smith 2006</td><td>China</td><td>1509</td><td>2004</td><td>286</td><td></td><td></td><td>Not defined</td><td></td><td>1</td><td></td><td>15.7</td><td></td></tr><tr><td>Smith 2007</td><td>New Zealand</td><td></td><td>1963–1996</td><td>22,097</td><td></td><td></td><td>Not defined</td><td></td><td>19–37</td><td></td><td>17.9</td><td></td></tr><tr><td>Sotiropoulos 2007</td><td>Greece</td><td>18,478</td><td>2003–2005</td><td>1284</td><td>55.9</td><td>38.4</td><td>Family medicine, Internal medicine, Biology, Others</td><td></td><td>13.8</td><td></td><td>38.6</td><td>58.3</td></tr><tr><td>Squier 2006</td><td>Ukraine</td><td>1048</td><td>2003</td><td>799</td><td>35.9</td><td>45</td><td>Family medicine</td><td></td><td>21.6</td><td></td><td>13.9</td><td></td></tr><tr><td>Steinberg 2007</td><td>USA</td><td>38,166</td><td>2002</td><td>334</td><td>70.7</td><td>49</td><td>Not defined</td><td></td><td>23</td><td></td><td>3.3</td><td></td></tr><tr><td>Stuyt 2009</td><td>USA</td><td>47,976</td><td>2007</td><td>1319</td><td>68.8</td><td>44.3</td><td>Family medicine, Internal medicine, Paediatry, Psychiatry, Emergency, Anesthesiology-Reanimation, Gynecology, Others</td><td></td><td>1</td><td></td><td>38.9</td><td>75.4</td></tr><tr><td>Sundquist 1999</td><td>Sweden</td><td>32774</td><td>1996</td><td>1004</td><td>46.2</td><td></td><td>Family medicine</td><td></td><td></td><td></td><td>8.4</td><td>50</td></tr><tr><td>Svärdsudd 2002</td><td>Sweden</td><td>24,225</td><td>1993–1999</td><td>974</td><td></td><td></td><td>Family medicine, Paediatry, Internal medicine, Psychiatry, Radiology, Orthopaedy, Ear Nose Throat, Gynecology, Others</td><td></td><td>3–43</td><td></td><td>7.5</td><td></td></tr></tbody></table>
<table><caption>Table 1. *Cont.*</caption><thead><tr><th rowspan="2">Study</th><th rowspan="2">Country</th><th rowspan="2">GDP per Capital</th><th rowspan="2">Period of Data Collection</th><th colspan="4">Physicians</th><th colspan="2">Prevalence (%) of</th><th colspan="2">Smokers</th><th rowspan="2">% Men among Smokers</th></tr><tr><th>n</th><th>% Men</th><th>Age</th><th>Speciality</th><th>Regular Smokers</th><th>Occasional Smokers</th><th>Former Smokers</th><th>Total (Regular & Occasional)</th></tr></thead><tbody><tr><td>Tapia-Conyer 1997</td><td>Mexico</td><td>5650</td><td>1993</td><td>3488</td><td>66.2</td><td>37</td><td>Not defined</td><td></td><td></td><td>20.6</td><td>26.9</td><td></td></tr><tr><td>Tee 2007</td><td>Malaysia</td><td>5594</td><td>2005</td><td>481</td><td>39.1</td><td></td><td>Study</td><td></td><td></td><td>2.7</td><td>1.7</td><td>75</td></tr><tr><td>Tessier 1996</td><td>France</td><td>22,380</td><td>1993</td><td>730</td><td>90</td><td>47</td><td>Cardiology</td><td>51.8</td><td>48.2</td><td>47</td><td>27</td><td></td></tr><tr><td>Thankappan 2008</td><td>India</td><td>541</td><td>2003</td><td>333</td><td>77.5</td><td>42.2</td><td>Not defined</td><td></td><td></td><td>26.1</td><td>10.8</td><td>100</td></tr><tr><td>Thomas 1986</td><td>USA</td><td>19,071</td><td></td><td>106</td><td>100</td><td>30.2–30.9</td><td>Not defined</td><td></td><td></td><td></td><td>13.2</td><td>100</td></tr><tr><td>Thomas 1997</td><td>USA</td><td></td><td>1957–1965</td><td>1015</td><td></td><td>24–27</td><td>Study</td><td></td><td></td><td></td><td>55.4</td><td></td></tr><tr><td>Tomson 2003</td><td>Laos</td><td>363</td><td></td><td>151</td><td>49.7</td><td></td><td>Not defined</td><td>46.2</td><td>53.8</td><td></td><td>17.2</td><td>100</td></tr><tr><td>Tong 2010</td><td>USA</td><td>39,497</td><td>2003–2004</td><td>1245</td><td>69.7</td><td></td><td>Emergency, Psychiatry, Others</td><td></td><td></td><td>18.4–28.8</td><td>3.5</td><td></td></tr><tr><td>Torre 2005</td><td>USA</td><td></td><td>1948–1964</td><td>1158</td><td>91.9</td><td></td><td>Not defined</td><td></td><td></td><td></td><td>51.1</td><td>91.7</td></tr><tr><td>Tosun 2016</td><td>Turkey</td><td>11,336</td><td>2011–2012</td><td>224</td><td>65.2</td><td>31.71</td><td>Not defined</td><td></td><td></td><td></td><td>28.1</td><td></td></tr><tr><td>Trédaniel 1993</td><td>France</td><td>16,302</td><td>1987</td><td>1012</td><td>87.5</td><td></td><td>Family medicine</td><td></td><td></td><td>29.1</td><td>36.9</td><td>89.3</td></tr><tr><td>Ulbricht 2009</td><td>Germany</td><td></td><td></td><td>37</td><td>51.4</td><td>47.5</td><td>Family medicine</td><td></td><td></td><td></td><td>24.3</td><td></td></tr><tr><td>Unal 2017</td><td>Turkey</td><td></td><td>1975–2004</td><td>7228</td><td>66</td><td>43.6</td><td>Not defined</td><td></td><td></td><td>22.5</td><td>23.9</td><td>75.3</td></tr><tr><td>Underner 2004</td><td>France</td><td>24,177</td><td>2002</td><td>257</td><td></td><td></td><td>Family medicine</td><td>60.6</td><td>39.4</td><td>30.7</td><td>25.7</td><td></td></tr><tr><td>Underner 2006</td><td>France</td><td>24,177</td><td>2002</td><td>257</td><td></td><td>48</td><td>Family medicine</td><td>61.2</td><td>38.8</td><td>31</td><td>26.1</td><td></td></tr></tbody></table>
<table><caption>Table 1. *Cont.*</caption><thead><tr><th rowspan="2">Study</th><th rowspan="2">Country</th><th rowspan="2">GDP per Capital</th><th rowspan="2">Period of Data Collection</th><th colspan="4">Physicians</th><th colspan="2">Prevalence (%) of Smokers</th><th colspan="2">Smokers</th><th rowspan="2">% Men among Smokers</th></tr><tr><th>n</th><th>% Men</th><th>Age</th><th>Speciality</th><th>Regular Smokers</th><th>Occasional Smokers</th><th>Former Smokers</th><th>Total (Regular & Occasional)</th></tr></thead><tbody><tr><td>Uysal 2007</td><td>Turkey</td><td>6041</td><td>2004</td><td>374</td><td>66.8</td><td>46</td><td>Not defined</td><td></td><td></td><td>29</td><td>16</td><td>70</td></tr><tr><td>Vanderhoek 2013</td><td>Canada</td><td>52,542</td><td>2012</td><td>301</td><td>48.5</td><td>24.4</td><td>Study</td><td></td><td></td><td></td><td>15.9</td><td></td></tr><tr><td>Vanphanom 2011</td><td>Laos</td><td>710</td><td>2007</td><td>855</td><td>52.9</td><td></td><td>Not defined</td><td>54.4</td><td>45.6</td><td>18.4</td><td>9.2</td><td>97.5</td></tr><tr><td>Varona 2005</td><td>Cuba</td><td>2308</td><td>1997</td><td>121</td><td>33.1</td><td></td><td>Family medicine</td><td></td><td></td><td></td><td>18.2</td><td>40.9</td></tr><tr><td>Viegas 2007</td><td>Brazil</td><td>4770</td><td>2005</td><td>830</td><td></td><td></td><td>Not defined</td><td>81.7</td><td>18.3</td><td>22.7</td><td>7.2</td><td></td></tr><tr><td>Voigt 2009</td><td>Germany</td><td>34,044</td><td>2004–2006</td><td>912</td><td></td><td></td><td>Not defined</td><td></td><td></td><td></td><td>13.7</td><td></td></tr><tr><td>Waalkens 1992</td><td>Netherlands</td><td>17,398</td><td>1989</td><td>1085</td><td>58.3</td><td></td><td>Study, Others</td><td></td><td></td><td>14.5–34</td><td>28.7</td><td>68.8</td></tr><tr><td>Wada 2007</td><td>Japan</td><td>37,218</td><td>2005</td><td>196</td><td>76</td><td></td><td>Not defined</td><td></td><td></td><td></td><td>19.4</td><td></td></tr><tr><td>Wada 2011</td><td>Japan</td><td>40,855</td><td>2009</td><td>3864</td><td>78.3</td><td></td><td>Not defined</td><td></td><td></td><td>12</td><td>14</td><td>90.6</td></tr><tr><td>Wang 2021</td><td>China</td><td>9977</td><td>2018</td><td>1046</td><td>61.2</td><td></td><td>Not defined</td><td></td><td></td><td></td><td>14.7</td><td></td></tr><tr><td>Wilf Miron 2019</td><td>Israel</td><td>35,776</td><td>2015</td><td>4832</td><td>59.7</td><td></td><td>Not defined</td><td></td><td></td><td></td><td>8.5</td><td></td></tr><tr><td>Willaing 2003</td><td>Denmark</td><td>33,441</td><td>1999</td><td>40</td><td></td><td></td><td>Not defined</td><td></td><td></td><td>23</td><td>25</td><td></td></tr><tr><td>Wilson 2020</td><td>Australia</td><td></td><td></td><td>251</td><td></td><td></td><td>Family medicine</td><td></td><td></td><td></td><td>21.1</td><td></td></tr><tr><td>Wyshak 1980</td><td>USA</td><td>11,674</td><td>1979</td><td>289</td><td>92</td><td></td><td>Not defined</td><td></td><td></td><td></td><td>13.8</td><td></td></tr><tr><td>Yaacob 1993</td><td>Malaysia</td><td>2654</td><td>1991</td><td>120</td><td>70.8</td><td></td><td>Not defined</td><td></td><td></td><td>13.3</td><td>17.5</td><td>100</td></tr><tr><td>Yan 2008</td><td>China</td><td>1289</td><td>2003</td><td>358</td><td></td><td></td><td>Not defined</td><td></td><td></td><td>10.6</td><td>35.8</td><td></td></tr><tr><td>Young 1997</td><td>Australia</td><td>21,861</td><td>1996</td><td>855</td><td></td><td></td><td>Family medicine</td><td></td><td></td><td></td><td>3.2</td><td></td></tr></tbody></table>
<table><caption>Table 1. *Cont.*</caption><thead><tr><th rowspan="2">Study</th><th rowspan="2">Country</th><th rowspan="2">GDP per Capital</th><th rowspan="2">Period of Data Collection</th><th colspan="4">Physicians</th><th colspan="2">Prevalence (%) of Smokers</th><th colspan="2">Smokers</th><th rowspan="2">% Men among Smokers</th></tr><tr><th>n</th><th>% Men</th><th>Age</th><th>Speciality</th><th>Regular Smokers</th><th>Occasional Smokers</th><th>Former Smokers</th><th>Total (Regular & Occasional)</th></tr></thead><tbody><tr><td>Zabadi 2018</td><td>Paslestine</td><td></td><td>2005</td><td>502</td><td>80.1</td><td>34.92</td><td>Family medicine, Study, Others</td><td></td><td></td><td>12.2</td><td>39.6</td><td>64.8</td></tr><tr><td>Zanetti 1998</td><td>Italy</td><td>23,020</td><td>1996</td><td>393</td><td>74</td><td></td><td>Not defined</td><td></td><td></td><td></td><td>31</td><td>68.9</td></tr><tr><td>Zhang 2012</td><td>China</td><td>4550</td><td>2010</td><td>84</td><td>38.1</td><td>39.4</td><td>Not defined</td><td>17.6</td><td>82.4</td><td>2</td><td>20.2</td><td></td></tr><tr><td>Zhang 2015</td><td>China</td><td>8069</td><td></td><td>8725</td><td></td><td></td><td>Study, Others</td><td></td><td></td><td></td><td>12.8</td><td>96.7</td></tr><tr><td>Zhou 2010</td><td>China</td><td>2694</td><td>2007</td><td>673</td><td>73.3</td><td></td><td>Not defined</td><td></td><td></td><td>5</td><td>26.2</td><td>96.6</td></tr><tr><td>Zinonos 2016</td><td>Cyprus</td><td>35,391</td><td>2008</td><td>119</td><td>59.7</td><td></td><td>Not defined</td><td></td><td></td><td>16</td><td>28.6</td><td></td></tr><tr><td>Zylbersztejn 2015</td><td>Argentina</td><td>13,080</td><td>2013</td><td>3033</td><td></td><td>41.3</td><td>Not defined</td><td></td><td></td><td>21.7</td><td>19.7</td><td></td></tr></tbody></table>
## 3.1. Quality of Articles

Using the NOS criteria for cross-sectional studies demonstrated a low risk of bias, except for sample size (not clearly defined in 75% of studies), representativeness (comparability bias in 82% of studies), and statistical tests (not or incompletely described in 49% of studies) (Figure 2). NOS for cross-sectional and cohort assessment are shown in Figure S1 in Supplement. STROBE and CONSORT assessment are shown in Table A1.

### Risk of bias summary
### Cross sectional Studies

<figure><img src="image_7.png" /><figcaption>**Figure 2.** Risk of bias using Newcastle Ottawa Scale composed by seven level of bias assessment.</figcaption></figure>

## 3.2. Study Designs and Objectives

Most (94%) studies were cross-sectional [7,8,21–250]. However, twelve were cohort [251–262] and two were clinical trials [263,264]. Every one of the included 246 studies described smoking prevalence among physicians. The main aim of examining smoking prevalence among physicians was reported in most studies (n = 117) [24,26,27,29,32,33,35–41,44,45,48,49,53–56,58,59,68,69,72,73,76,78,82,84,85,87,90–95,97–99,102–104,107,108,110,115,119–121,126,131–133,135–138,141,142,144–149,151,154,156–158,160,161,163–165,167,169–172,174,176,178–180,182,183,185,187,189–194,196,197,199,201–204,207,211,213,218,224,225,227,231,239,241–243]. Fifteen studies also aimed to assess the use of other substances in physicians [29,37,93–95,117,118,124,141,161,165,171,193,239,248]. Other outcomes presented were demographic characteristics and health status of physicians in 58 studies [22,23,30,31,42,43,46,57,60,63–66,74,75,80,88,89,96,100,106,114,116,123,125,128–130,134,139,143,153,155,162,176,177,181,184,195,198,208,223,238,239,249,251–261,263,264], the evaluation of smoking cessation counselling among physicians in 50 studies [25,26,28,33,35,40,55,61,62,67,70,79,86,92,97,99,101,104,105,111,136,142,144,145,152,157,168,183,189–191,197,201,203–205,209,210,212,214,218,219,234–236,241,242,244,247,250], the attitude of physicians towards prevention and promotion of a healthy lifestyle in seven studies [122,140,206,208,220,222,228], the knowledge on tobacco effects in 20 studies [24,33,39,44,50,53,61,62,78,91,98,119,154,178,199,204,216,217,240,247], and the examination of the link between smoking habits of physicians and their practice of providing minimal smoking cessation advice in 26 studies [7,8,21,47,58,81,83,109,112,127,150,159,175,186–188,208,211,213,224,225,232,237,244,246,262]. Finally, the primary outcome was not clearly defined in 16 studies [34,51,52,71,77,113,166,173,200,215,221,226,229,230,233,245].

## 3.3. Recruitment of Physicians

Physicians were recruited from health centers in 94 studies, either monocentric in 50 studies [21,26,29,30,37,41–43,46,49,56,79,80,97,115,120,121,132–134,156,162,163,167,170,179,181,182,184,190,193,194,196,202,204,212,217,225,228,229,232,235,244,250,256,257,259,260,263,264] or multicentric in 44 studies [24,39,53,54,72,83,89–92,98,111,112,117,119,123,126,128,130,131,141,152,168,169,178,197,201,203,205,207,214,216,219,220,224,227,231,236–238,242,243,253,261]. They were also recruited from specific lists in 68 studies, either
from specific societies in 14 studies [22,40,47,77,78,110,158,180,183,189,221,222,230,240],
associations in 23 studies [7,59,67,87,94,95,106–108,118,129,135,142,206,209,223,234,239,245,
249,251,254,262], medical or specific registers in 22 studies, [23,38,85,88,113,127,139,144,
145,154,159,165,173,177,186,192,199,208,210,246,248,258] and lists from ministries of health
in 9 studies [33,35,45,99,116,140,146,166,218]. Finally, recruitment procedure was not de-
fined in 84 studies [8,25,27,28,31,32,34,36,44,48,50–52,55,57,58,60–66,68–71,73–76,81,82,84,86,
93,96,100–105,109,114,122,124,125,136–138,143,147–151,153,155,157,160,161,164,171,172,174–
176,185,187,188,191,195,198,200,211,213,215,226,233,241,247,252,255]. Smoking prevalence
was also described in non-physicians in 30 studies [24,39,40,52,69,74,79,86,91,99,102,104,
105,110,113,125,129,133,135,139,143,151,161,162,176,185,195,197,202,235].

3.4. Populations Studied

**Sample size** ranged from 17 [235,237] to 31,208 [64]. In total, 497,081 physicians were included in this meta-analysis.

**Age** of physicians was reported in 89 studies. Overall, the mean age was 41.5 years old (95%CI 38.4 to 44.6), ranging from 20.2 [132] to 59.8 [109] years old (Table 1).

**Gender** was reported in more than half of the studies (n = 165) on the total population of physicians, among which 107 studies also reported gender of smoking physicians. The mean number of men was 62% (58 to 65%), ranging from 0 in five studies that included only women, to 100% in thirteen studies that included only men (Table 1).

**Specialty** was reported in 96 studies. Family practitioners were the most represented (56 studies, n = 64,187 physicians), followed by medical students (27 studies, n = 28,564), medical specialties (39 studies, n = 15,538), anesthesiologists (15 studies, n = 3329), surgical specialties (17 studies, n = 2395), pediatrics (11 studies, n = 1847), psychiatrists (8 studies, n = 1393), and radiologists (7 studies, n = 1193) (Table 1).

**Location** of studies was always reported. Most studies were conducted in Europe (89 studies, n = 20,509), followed by America (56 studies, n = 126,615), Asia (83 studies, n = 104,325), Oceania (13 studies, n = 59,609), and Africa (8 studies, n = 2023) (Table 1).

**Other variables** were less well described. Family status was reported in 29 studies [22,42,45,74,79,85,89,92–94,103,105,112,121,125,128,130,137,143,161,174,179,195,199,229,244,250,257,264], workplace was the focus in 42 studies (most worked in public sectors) [22,28,40,47,58,61,75,79,88,94,96,104,105,125,130,133–135,137,148–150,155,161,163,172,174,180,185,186,189,199,203,218,219,223,226,229,234,239,240,242], working hours per week was reported in 8 studies (ranging from 37 [25] to 79 [80] hours per week) [22,25,58,75,80,143,195,213], seniority of physician was reported in 14 studies (ranging from 6.5 [205] to 20.8 [28] years ago) [25,28,36,58,78,96,126,130,137,140,150,184,204,205], BMI in 17 studies (ranging from 21 [260] to 27.7 [257] kg/m²) [23,30,42,66,80,88,96,130,139–141,244,249,255,257,259,260], and physical activity in 24 studies (most physicians were active) [30,42,46,57,75,88,89,96,100,121–123,125,129,130,134,139,140,143,195,238,239,255,257].

3.5. Smoking Assessment

Most studies used a self-administered questionnaire (postal and email) (209 stud-
ies) [7,8,21–33,36–54,56,57,59–72,75–88,90–96,98,99,102,105–109,111,112,114,116–135,137,139–
149,151,153,154,157–174,176–182,184–186,189,190,192–199,201–203,205–207,209–215,217–225,
227–232,234–242,244–246,248–257,259,260,262–264]. Other studies collected data by inter-
view (11 studies) [35,55,100,101,150,155,156,175,191,208,261], interview and postal (7 stud-
ies) [58,73,74,115,183,187,188], phone (9 studies) [89,103,104,136,152,204,216,226,233], and
phone and postal (1 study) [98]. The data collection method was unclear in nine stud-
ies [34,97,110,113,138,200,243,247,258]. The definition of smoking used was not explained
in most (96.2%) included articles. In eight studies, smoking was defined by one cigarette
per day [24,93,142,156,162,202,203,220]. In five studies, a smoker was defined as a person
who had smoked at least 100 cigarettes or an equivalent amount of tobacco in their
lifetime [24,138,178,202,261]. Two studies specified whether smokers were cigarette, pipe,
or cigar smokers [114,115]. Around half of the studies reported the prevalence of ex-
smokers (135 studies, *n* = 47,688) (Table 1). As with smoking, the definition of ex-smoking was not explained in most (95.2%) included articles. In five studies, an ex-smoker was defined as someone who stopped smoking completely for at least 3 [220], 6 [142,261], or 12 months [24,224]. Publication occurred within 2 years of data collection for 31% of studies, within 2 to 5 years for 45%, and more than 5 years for 10%—and was not reported for 14% of studies. Most studies were published between 2000 and 2015 (138 studies, *n* = 232,323), followed by studies published between 1985 and 2000 (54 studies, *n* = 85,402), after 2015 (31 studies, *n* = 94,637), and before 1985 (23 studies, *n* = 84,719). Studies ranged from 1954 [63] to 2021 [243,247] (Table 1).

### 3.6. Meta-Analysis on the Smoking Prevalence among Physicians

The smoking prevalence among physicians was around 21% (95CI 20 to 23%). Stratified by specialty, prevalence of smoking was 25% (21 to 29%) in medical students, 24% (22 to 26%) in family practitioners, 18% (12 to 23%) in surgical specialties, 17% (10 to 23%) in psychiatrists, 16% (14 to 17%) in medical specialties, 11% (8 to 15%) in anesthesiologists, 9% (5 to 13%) in radiologists, and 8% (6 to 11%) in pediatrics. Stratification by continent showed the prevalence of smoking in physicians ranging from 11% in Oceania to 25% in Europe and Asia. The smoking prevalence among physicians decreased over time: 28% (22 to 33%) before 1985, 22% (19 to 25%) between 1985 and 2000, 20% (19 to 21%) between 2000 and 2015, and 16% (14 to 18%) after 2015. All I² were extremely high within each stratification, i.e., >99%, except two I² that were at 86 and 94% (Figure 3).

### 3.7. Meta-Regressions

Family practitioners and medical students had a higher smoking prevalence than anesthesiologists (Coefficient 0.12, 95CI 0.04 to 0.19, and 0.12, 0.03 to 0.20, respectively), pediatrics (0.12, 0.03 to 0.21 and 0.13, 0.03 to 0.23), radiologists (0.12, 0.02 to 0.22, and 0.12, 0.02 to 0.23), and other medical specialties (0.07, 0.01 to 0.12, and 0.08, 0.01 to 0.15). For comparisons between continents, physicians in Europe and Asia had a higher smoking prevalence than in North America (0.07, 0.04 to 0.11, and 0.08, 0.04 to 0.11, respectively) and Oceania (0.12, 0.09 to 0.16, and 0.13, 0.08 to 0.17). Smoking prevalence in North America was also significantly higher than in Oceania (0.05, 0.01 to 0.09). Lastly, smoking prevalence was the highest before 1985 (0.06, 0.01 to 0.10 vs. between 1985 to 2000; 0.08, 0.04 to 0.12 vs. between 2000 to 2015; 0.11, 0.05 to 0.16 vs. after to 2015). Moreover, the smoking prevalence between 1985 and 2000 was higher than after 2015 (0.05, 0.01 to 0.09). Male physicians had a higher smoking prevalence than women (0.01, 0.00 to 0.01). Age did not influence smoking prevalence (Figure 4). Insufficient data precluded other meta-regressions.

### 3.8. Sensitivity Analyses

Funnel plots of meta-analyses analyzing for potential publication bias are presented in Figure 2. Due to the huge heterogeneity (most I² being >99%), we did not reperform meta-analyses after the exclusion of studies that were not evenly distributed around the base of the funnel. Lastly, we performed all aforementioned analyses on the prevalence of ex-smokers. The prevalence of ex-smokers among physicians was around 23% (95CI 21 to 25%). Psychiatrists also had a high prevalence of ex-smokers (29%, 19 to 40%), followed by other specialties. Contrary to meta-analyses on current smokers, medical students had a low rate of ex-smokers (11%, 6 to 17%). Interestingly, if prevalence of current smokers was similarly high in Europe and Asia (25%), there was greater prevalence of ex-smokers in Europe (25%, 21 to 29%) than in Asia (17, 14 to 20%) (*p* < 0.001). North America and South America also had a high prevalence of ex-smokers (27%, 20 to 34%; and 26%, 14 to 38%, respectively), whereas Africa had a low prevalence of ex-smokers (8%, 6 to 10%). The prevalence of ex-smokers decreased in similar proportions over time: 31% (26 to 35%) before 1985, 24% (18 to 30%) between 1985 and 2000, 22% (19 to 24%) between 2000 and 2015, and 21% (14 to 28%) after 2015 (Figures 3 and 4).
<table><caption>**Figure 3.** Meta-analysis on prevalence among physicians stratified by specialty, continent, and time. Results are expressed in percentage from 0 to 100. Bold represent a stratification or overall result.</caption><thead><tr><th>Variables</th><th>n studies<br>(n subgroups)</th><th></th><th>Percentage of smokers (95CI)</th><th>Weight (%)</th></tr></thead><tbody><tr><td><strong>By speciality</strong></td><td></td><td></td><td></td><td></td></tr><tr><td>Medical students</td><td>27 (36)</td><td>◆</td><td>25% (21 to 29%)</td><td>5.9</td></tr><tr><td>Family medicine</td><td>56 (93)</td><td>◆</td><td>24% (22 to 26%)</td><td>16.5</td></tr><tr><td><strong>Surgical specialities</strong></td><td></td><td></td><td></td><td></td></tr><tr><td>Chest surgery</td><td>1 (1)</td><td>-O-</td><td>13% (10 to 16%)</td><td>0.2</td></tr><tr><td>Ear Nose Throat</td><td>3 (4)</td><td>-O-</td><td>21% (10 to 31%)</td><td>0.4</td></tr><tr><td>Gynecology</td><td>10 (14)</td><td>-O-</td><td>20% (13 to 26%)</td><td>2.4</td></tr><tr><td>Ophtalmology</td><td>1 (1)</td><td>O-</td><td>2% (1 to 5%)</td><td>0.2</td></tr><tr><td>Orthopaedy</td><td>2 (2)</td><td>-O-</td><td>5% (1 to 9%)</td><td>0.4</td></tr><tr><td>Overall surgical specialities</td><td>17 (21)</td><td>◆</td><td>18% (12 to 23%)</td><td>3.6</td></tr><tr><td>Psychiatry</td><td>8 (8)</td><td>◆</td><td>17% (10 to 23%)</td><td>1.4</td></tr><tr><td><strong>Medical specialities</strong></td><td></td><td></td><td></td><td></td></tr><tr><td>Biology</td><td>2 (2)</td><td>-O-</td><td>24% (17 to 31%)</td><td>0.3</td></tr><tr><td>Cardiology</td><td>5 (5)</td><td>-O-</td><td>13% (4 to 23%)</td><td>0.9</td></tr><tr><td>Dermatology</td><td>1 (1)</td><td>-O-</td><td>16% (7 to 32%)</td><td>0.2</td></tr><tr><td>Emergency</td><td>5 (5)</td><td>-O-</td><td>13% (5 to 21%)</td><td>0.9</td></tr><tr><td>Internal medicine</td><td>14 (14)</td><td>-O-</td><td>22% (13 to 30%)</td><td>2.5</td></tr><tr><td>Oncology</td><td>1 (1)</td><td>-O-</td><td>27% (18 to 39%)</td><td>0.2</td></tr><tr><td>Pathology</td><td>4 (4)</td><td>-O-</td><td>11% (3 to 19%)</td><td>0.7</td></tr><tr><td>Pneumology</td><td>5 (5)</td><td>-O-</td><td>12% (2 to 22%)</td><td>0.9</td></tr><tr><td>Public health</td><td>2 (2)</td><td>-O-</td><td>23% (13 to 33%)</td><td>0.3</td></tr><tr><td>Overall medical specialities</td><td>39 (39)</td><td>◆</td><td>16% (14 to 17%)</td><td>6.9</td></tr><tr><td>Anesthesiology</td><td>15 (16)</td><td>◆</td><td>11% (8 to 15%)</td><td>2.9</td></tr><tr><td>Radiology</td><td>7 (9)</td><td>◆</td><td>9% (5 to 13%)</td><td>1.6</td></tr><tr><td>Paediatry</td><td>11 (11)</td><td>◆</td><td>8% (6 to 11%)</td><td>2.1</td></tr><tr><td>Undefined</td><td>150 (307)</td><td>◆</td><td>21% (19 to 24%)</td><td>59.1</td></tr><tr><td><strong>By continent</strong></td><td></td><td></td><td></td><td></td></tr><tr><td>Europe</td><td>89 (221)</td><td>-O-</td><td>25% (21 to 28%)</td><td>2.2</td></tr><tr><td>Asia</td><td>83 (137)</td><td>-O-</td><td>25% (22 to 27%)</td><td>24.0</td></tr><tr><td>Central America</td><td>1 (1)</td><td>-O-</td><td>18% (12 to 26%)</td><td>0.17</td></tr><tr><td>North America</td><td>46 (116)</td><td>O-</td><td>17% (15 to 18%)</td><td>38.2</td></tr><tr><td>South America</td><td>9 (9)</td><td>-O-</td><td>17% (10 to 24%)</td><td>21.3</td></tr><tr><td>Africa</td><td>8 (12)</td><td>-O-</td><td>17% (11 to 23%)</td><td>12.1</td></tr><tr><td>Oceania</td><td>13 (67)</td><td>O-</td><td>11% (10 to 13%)</td><td>1.7</td></tr><tr><td><strong>By time</strong></td><td></td><td></td><td></td><td></td></tr><tr><td>> 2015</td><td>31 (76)</td><td>O-</td><td>16% (14 to 18%)</td><td>10.9</td></tr><tr><td>2000–2015</td><td>138 (288)</td><td>O</td><td>20% (19 to 21%)</td><td>52.0</td></tr><tr><td>1985–2000</td><td>54 (141)</td><td>O</td><td>22% (19 to 25%)</td><td>25.5</td></tr><tr><td>&lt; 1985</td><td>23 (65)</td><td>O</td><td>28% (22 to 33%)</td><td>11.6</td></tr><tr><td><strong>Overall</strong></td><td><strong>246 (570)</strong></td><td>◆</td><td><strong>21% (20 to 23%)</strong></td><td><strong>100.0</strong></td></tr></tbody></table>
<figure><img src="image_8.png" /><figcaption>**Figure 4.** Meta-regressions. "means 'same as' the line above. Bold represent a stratification.</figcaption></figure>

## 4. Discussion

The main findings were that the prevalence of smoking among physicians is high, around 21%. Family practitioners and medical students have the highest percentage of smokers and should benefit from targeted preventive strategies. Smoking in physicians is a public health issue that is common, both in developed and developing countries, even if quitting smoking is higher in developed countries. Positively, the prevalence of smoking decreased over time.
## 4.1. Smoking among Physicians: A Public Health Issue

Surprisingly, prevalence of smoking among physicians is high, which may seem unlikely because they should be an example for their patients and should know the health risks linked to tobacco [21]. This said, even if there is no study determining whether being a physician is a risk factor for smoking compared to the general population, they seem to follow similar trends and are highly concerning [265]. Literature shows that disadvantaged populations smoke more than others [266]. In some way, physicians can also be considered as disadvantaged due to their cumulative risk factors for smoking. They face a huge workload, working over 55 h a week [22]. Stress at work could play a major role in their smoking habits [22]. Overload of stress can even contribute to depressive disorders and high risk of suicides, that are also risk factors of smoking [267,268]. They also work nightshifts [43], disrupting the circadian rhythm that can heighten smoking behavior [269]. Moreover, despite the consequences for themselves, physicians who smoke are less likely to promote quitting smoking for their patients [7,21]. Therefore, there is a need to tackle physicians smoking behavior both for themselves and their patients. Smoking in physicians must be considered as a major public health problem. Alarmingly, even our massive search did not find governmental actions for quitting smoking in physicians. In the research, we found several randomized controlled trials on strategies for smoking cessation in homeless people [270,271], but none in physicians.

## 4.2. Depending on Specialties

The smoking prevalence was higher among medical students and family practitioners. For medical students, the high prevalence of smoking may be explained due to the stress of hard academic studies [272]. Moreover, medical students can have high risk-taking behaviors such as partying and tobacco consumption [273,274]. The high prevalence among family practitioners might be explained by several putative factors such as workload [22], stress [22], and lack of cohesive teamwork [275]. Workload and stress have been shown in the literature as an important risk factor of smoking [22]. The work environment, such as the lack of cohesive teamwork, is a risk factor of depression and drug use [275], with depression and drug use being linked [60]. Similarly, workload [22] and work stress [22] can also contribute to the high prevalence of smoking in surgical practitioners, who can face legal issues as part of their work [276]. Experiencing judgement in court and repeated trials could promote depression and, in turn, smoking [276]. For psychiatrists, contributing factors of smoking could be the fact that they are routinely faced with traumatic experiences [277], incurable diseases [278], and breaking bad news to patients [278]. Conversely, pediatrics smoked the least, probably because they most often deal with common and curable diseases [279]. Moreover, pediatricians are predominantly women [280]. Although we found a higher prevalence of smoking among women, the literature described a lower rate of smoking among women compare to men in the general population [45,243]. A common characteristic of all specialties is that smoking cessation training during medical studies was poor or not important enough [62,70]. This may contribute to the high prevalence of smoking among physicians. Considering that nearly all physicians will encounter smoking patients, improving smoking cessation training during their studies could help both their patients to quit smoking, as well as the physicians themselves.

## 4.3. Depending on Continents

Smoking prevalence was not homogeneous between continents. Europe and Asia were continents where the smoking prevalence among physicians was the highest. Conversely, Oceania was the continent where the smoking prevalence among physicians was the lowest. This heterogeneous prevalence was probably in line with tobacco culture [281] and tobacco marketing [281] in many countries. Tobacco culture in Europe was brought by Christopher Columbus in the 16th century [282], firstly as a luxury product [13]. But during the 20th century, tobacco became accessible for all and became a trendy product [13]. Then, in developed countries, tobacco became undesirable [283]. Recent literature shows
that tobacco marketing targeted more poor countries [284]. India is the country on the Asian continent with the poorest population, and represents about 17% of the global population [285–287]. Moreover, tobacco control is less important in Asia [288]. Studies conducted in Oceania were conducted in rich countries, i.e., Australia and New Zealand, that may be the two countries with the strongest anti-smoking policy [289]. In those two countries, the price of cigarettes is among the most expensive. The increasing taxes aided the decrease in prevalence of smoking, which can be an easy reproducible preventive strategy in other countries [290]. In 2012, Australia was the first country to use plain cigarette packaging [291,292]. A national tobacco campaign in Australia showed the benefits of stopping smoking rather than the negative effects of tobacco [293]. In New Zealand, smoking is prohibited in motor vehicles carrying children under the age of 18 [294]. Finally, except in those two countries that manage smoking, smoking is still a major public health issue worldwide, both in developed and developing countries.

### 4.4. With a Time Effect

The smoking prevalence among physicians decreased overtime. We showed that physicians' smoking prevalence has decreased since 1985. The knowledge of the health risks of tobacco during the 1970s changed tobacco from a positive to a negative image [13]. The most recent studies (after 2015) showed that the prevalence of tobacco in physicians continued to decrease. Universally, this decrease was probably related to the tobacco control implemented by the WHO [295], such as a tobacco free-day since 1987 [296]. The WHO Framework Convention on demand and supply reduction [295] probably played a major role in the tobacco consumption decline. Since 2003, European directives limit physicians' work to 48 h per week [297,298], which may have lessened the stress of physicians. The development of new technologies has encouraged public health advocates to adapt to target a younger cohort, such as the creation of a mobile app for assisting smokers [299], sending emails [300], or sending mobile text messaging [300]. Even if the number of studies on the toxicity of electronic cigarettes remains low, it seems interesting to help with smoking cessation [301]. In Canada, mailed distribution of free nicotine patches seems beneficial, particularly among the financially disadvantaged [302]. In France, nicotine substitutes are reimbursed at 65% by the National Health system as of January 2019 [303]. Our meta-analysis showed that many studies were carried out between 2000 and 2015, probably to assess the effectiveness of tobacco control [295]. Interestingly, preventive strategies sometimes took advantage of context. With the COVID pandemic, Santé Publique France led a digital campaign and special operation to promote the tobacco control [304], based on the fact that tobacco aggravates COVID's symptoms [305]. That said, the decrease in smoking prevalence could continue in the coming years.

### 4.5. Other Influencing Variables

Male physicians always smoked more than women, probably because of social habit [306]. There was no significant effect of age on the smoking prevalence of physicians, however, smoking prevalence among the general population decreases with age [307,308]. Insufficient data precluded further analyses on putative influencing factors such as physical activity, BMI, number of hours worked per week, workplace setting, or family status. For example, lower physical activity and higher waist circumference were associated with tobacco consumption [309]. Leisure physical activity of physicians is low [310], which can be limited by their workload [310]. Low levels of physical activity also contribute to burnout [311], that, in turn, increases smoking [22]. No study compared smoking prevalence based on the type of practice (public or private practice). Even if being divorced or separated is a risk factor for smoking in the general population [312,313], the influence of family status in physicians has not been reported. To our knowledge, smoking prevalence of physicians was never compared with smoking prevalence of the general population. Physicians also have protective factors of smoking. For example, their level of study is above the baccalaureate [307], their income is higher than the average population [307],
and they are most likely to know tobacco risks [21]. Considering that physicians combine
risk and protective factors of smoking, comparisons with the general population may be of
particular interest to target appropriate preventive strategies.

4.6. *Limitations*

Our study has some limitations. We conducted our meta-analyses on only published articles, so our results were, theoretically, exposed to a publication bias. We included only studies reporting physicians’ smoking prevalence and only studies written in English or French, so our results were, theoretically, exposed to a selection bias. Most cross-sectional studies included in our meta-analysis described a bias of self-report. Data were collected by self-administered questionnaire, not always anonymously. Thus, the reporting of smoking might have been underestimated by physicians. Another limitation could be the number of different studies included and the number of physicians included. Although we did not find any double inclusion, it could be possible that some physicians were included twice, creating an overlap that might introduce some bias. Our meta-analysis also had limitations on the definition of smoking. In fact, the definition used to define regular smokers, occasional smokers, or former smokers was different between studies and was rarely detailed. Therefore, the meta-analysis inherited the limitations of the individual studies of which they were comprised: varying quality of studies, multiple variations in study protocols, and evaluation. Comparisons between specialties might suffer from a bias, such as a different number of physicians within each specialty. Moreover, our meta-analysis had a lot of studies with undefined specialties. Similarly, some authors suggested that the medical field was mainly dominated by the male gender and reported a poor status integration of women physicians within the profession [314]. Comparisons between continents or time period might also suffer from a different number of studies within each continent or each period; however, our review provided a massive sample of nearly half a million physicians promoting generalizability of our results.

**5. Conclusions**

We found that the prevalence of smoking among physicians is high, around 21%. There is an important heterogenicity between specialties, continents, and periods of time. Despite family practitioners and medical students being the heaviest smokers, all physicians should benefit from targeted preventive strategies. Smoking in physicians is a public health issue that is common, both in developed and developing countries, even if quitting smoking is higher in developed countries. Positively, the prevalence of smoking decreased over time, but pursing tobacco control is necessary.

**Supplementary Materials:** The following are available online at https://www.mdpi.com/article/10.3390/ijerph182413328/s1: Figure S1, Funnel plots; Figure S2, Meta-analysis on prevalence of ex-smokers among physicians; Figure S3, Comparisons.

**Author Contributions:** Conceptualization, F.D.; methodology, F.D.; formal analysis, F.D.; investigation, A.T. and A.B. (Amanda Benson); data curation, A.T. and A.B. (Amanda Benson); writing—original draft preparation, A.B. (Anaïs Besson) and A.T.; writing—review and editing, V.F., G.B., C.L., V.N., F.D. and J.-B.B.-M.; visualization, F.D.; supervision, F.D. All authors have read and agreed to the published version of the manuscript.

**Funding:** This research received no external funding.

**Institutional Review Board Statement:** Not applicable.

**Informed Consent Statement:** Not applicable.

**Data Availability Statement:** All relevant data are within the paper.

**Acknowledgments:** To Nathalie Pinol-Domenech for her availability.

**Conflicts of Interest:** The authors declare no conflict of interest.
# Appendix A. Details for the Search Strategy Used within Each Database

## Pubmed

"Smoking"[Mesh:NoExp] OR "smokings"[TW] OR "smoking"[TW] OR "Tobacco Smoking"[MH] OR "Smokers"[MH] OR "smoker"[TW] OR "Smokers"[TW] OR "tobacco"[Title]

AND

"family doctor"[TW] OR "general practitioner"[TW] OR "general practitioners"[TW] OR "practitioner, general"[TW] OR "practitioners, general"[TW] OR "general physician"[TW] OR "general physicians"[TW] OR "physicians, family"[TW] OR "family physicians"[TW] OR "family physician"[TW] OR "physician, family"[TW] OR "physicians, primary care"[TW] OR "physician, primary care"[TW] OR "primary care practitioner"[TW] OR "primary care physician"[TW] OR "primary care physicians"[TW] OR "medical practitioner"[TW] OR "physicians"[MH] OR "physicians"[Title] OR "physician"[Title] OR "doctor"[title] OR "doctors"[title] OR "practitioner"[Title] OR "practitioners"[Title]

AND

"prevalence"[MH] OR "prevalence"[TW] OR "prevalences"[TW] OR "epidemiology"[MH] OR "episode of care"[TW] OR "epidemiological"[TW] OR "epidemiologic"[TW] OR "epidemiology"[TW] OR "epidemiology"[SH] OR "frequency"[TIAB] OR "morbidity"[TIAB] OR "epidemics"[TIAB] OR "outbreaks"[TIAB] OR "endemics"[TIAB] OR "occurrence"[TIAB] OR "surveillance"[TIAB] OR "incidence"[TIAB]

## Embase

'health personnel attitude'/exp AND 'smoking/exp AND 'physician'/exp

## Cochrane

"smokings":ti,ab,kw OR "smoking":ti,ab,kw OR "smoker":ti,ab,kw OR "Smokers":ti,ab,kw OR tobacco:ti,ab,kw

AND

"physicians, family":ti,ab,kw OR "physicians, primary care":ti,ab,kw OR "family doctor":ti,ab,kw OR "general practitioner":ti,ab,kw OR "general practitioners":ti,ab,kw OR "practitioner, general":ti,ab,kw OR "practitioners, general":ti,ab,kw OR "general physician":ti,ab,kw OR "general physicians":ti,ab,kw OR "physicians, family":ti,ab,kw OR "family physicians":ti,ab,kw OR "family physician":ti,ab,kw OR "physician, family":ti,ab,kw OR "physicians, primary care":ti,ab,kw OR "physician, primary care":ti,ab,kw OR "primary care practitioner":ti,ab,kw OR "primary care physician":ti,ab,kw OR "primary care physicians":ti,ab,kw OR "physicians":ti,ab,kw OR "doctor":ti,ab,kw OR "doctors":ti,ab,kw OR "medical practitioner":ti,ab,kw OR "physicians":ti,ab,kw OR "physicians":ti OR "physician":ti OR "doctor":ti OR "doctors":ti OR "practitioners":ti OR "practitioner":ti

AND

"prevalence":ti,ab,kw OR "prevalences":ti,ab,kw OR "epidemiology":ti,ab,kw OR "episode of care":ti,ab,kw OR "epidemiological":ti,ab,kw OR "epidemiologic":ti,ab,kw OR "frequency":ti,ab,kw OR "morbidity":ti,ab,kw OR "epidemics":ti,ab,kw OR "outbreaks":ti,ab,kw OR "endemics":ti,ab,kw OR "occurrence":ti,ab,kw OR "surveillance":ti,ab,kw

<table><caption>**Table A1.** Methodological assessment of studies using STROBE and CONSORT criteria.</caption><thead><tr><th rowspan="2"></th><th colspan="5">STROBE</th></tr><tr><th>Total Score</th><th>Abstract Introduction</th><th>Methods</th><th>Results</th><th>Discussion</th></tr></thead><tbody><tr><td>Aaro 1977</td><td>60</td><td>100</td><td>36</td><td>60</td><td>75</td></tr><tr><td>Abdullah 2006</td><td>59</td><td>100</td><td>69</td><td>30</td><td>75</td></tr><tr><td>Aboyans 2009</td><td>56</td><td>100</td><td>31</td><td>50</td><td>100</td></tr></tbody></table>
<table><caption>Table A1. *Cont.*</caption><tr><td>Akvardar 2004</td><td>53</td><td>100</td><td>38</td><td>40</td><td>75</td></tr><tr><td>Al Alwan 2013</td><td>50</td><td>100</td><td>31</td><td>40</td><td>100</td></tr><tr><td>Alarjan 2015</td><td>53</td><td>100</td><td>46</td><td>40</td><td>75</td></tr><tr><td>al-Khateeb 1990</td><td>38</td><td>100</td><td>31</td><td>30</td><td>25</td></tr><tr><td>Allan 1976</td><td>13</td><td>0</td><td>NA</td><td>20</td><td>NA</td></tr><tr><td>Al-Lawati 2009</td><td>44</td><td>100</td><td>23</td><td>20</td><td>100</td></tr><tr><td>Al Shahrani 2021</td><td>69</td><td>100</td><td>69</td><td>60</td><td>75</td></tr><tr><td>An 2004</td><td>66</td><td>100</td><td>69</td><td>50</td><td>75</td></tr><tr><td>Amara 2008</td><td>53</td><td>100</td><td>38</td><td>40</td><td>100</td></tr><tr><td>Amte 2015</td><td>56</td><td>100</td><td>38</td><td>50</td><td>100</td></tr><tr><td>Arnetz 1988</td><td>66</td><td>100</td><td>54</td><td>60</td><td>75</td></tr><tr><td>Aryayev 2014</td><td>48</td><td>100</td><td>31</td><td>33</td><td>100</td></tr><tr><td>Baltaci 2014</td><td>53</td><td>100</td><td>38</td><td>40</td><td>75</td></tr><tr><td>Baptista 1993</td><td>44</td><td>100</td><td>31</td><td>30</td><td>100</td></tr><tr><td>Barengo 2004</td><td>45</td><td>100</td><td>42</td><td>33</td><td>50</td></tr><tr><td>Barengo 2005</td><td>44</td><td>100</td><td>23</td><td>30</td><td>100</td></tr><tr><td>Barnoya 2002</td><td>28</td><td>50</td><td>0</td><td>20</td><td>100</td></tr><tr><td>Basnyat 2000</td><td>34</td><td>100</td><td>10</td><td>20</td><td>100</td></tr><tr><td>Basu 2011</td><td>47</td><td>100</td><td>23</td><td>40</td><td>100</td></tr><tr><td>Behbehani 2004</td><td>50</td><td>100</td><td>54</td><td>20</td><td>75</td></tr><tr><td>Belkić 2007</td><td>59</td><td>100</td><td>38</td><td>50</td><td>100</td></tr><tr><td>Belkić 2012</td><td>56</td><td>100</td><td>54</td><td>30</td><td>100</td></tr><tr><td>Bener 1993</td><td>38</td><td>100</td><td>15</td><td>30</td><td>50</td></tr><tr><td>Borgan 2014</td><td>47</td><td>100</td><td>31</td><td>20</td><td>100</td></tr><tr><td>Bortz 1992</td><td>29</td><td>75</td><td>10</td><td>30</td><td>50</td></tr><tr><td>Bostan 2015</td><td>56</td><td>100</td><td>46</td><td>40</td><td>75</td></tr><tr><td>Bourke 1972</td><td>41</td><td>100</td><td>23</td><td>30</td><td>50</td></tr><tr><td>Braun 2004</td><td>41</td><td>100</td><td>31</td><td>30</td><td>25</td></tr><tr><td>Brenner 1996</td><td>56</td><td>100</td><td>46</td><td>40</td><td>100</td></tr><tr><td>Brink 1994</td><td>53</td><td>100</td><td>46</td><td>50</td><td>50</td></tr><tr><td>Brotonsc 2005</td><td>53</td><td>100</td><td>46</td><td>30</td><td>75</td></tr><tr><td>Burgess 1970</td><td>19</td><td>50</td><td>10</td><td>20</td><td>25</td></tr><tr><td>Burgess 1978</td><td>28</td><td>75</td><td>23</td><td>20</td><td>50</td></tr><tr><td>Cao 2011</td><td>41</td><td>50</td><td>25</td><td>44</td><td>75</td></tr><tr><td>Carlos 2020</td><td>70</td><td>100</td><td>62</td><td>60</td><td>75</td></tr><tr><td>Ceraso 2009</td><td>59</td><td>100</td><td>46</td><td>40</td><td>100</td></tr><tr><td>Chaudhry 2009</td><td>32</td><td>100</td><td>17</td><td>20</td><td>50</td></tr><tr><td>Cheng 1990</td><td>45</td><td>100</td><td>25</td><td>40</td><td>75</td></tr><tr><td>Coe 1971</td><td>34</td><td>50</td><td>15</td><td>30</td><td>75</td></tr><tr><td>Cofta 2008</td><td>50</td><td>100</td><td>38</td><td>30</td><td>75</td></tr><tr><td>Das 2013</td><td>53</td><td>100</td><td>46</td><td>30</td><td>75</td></tr><tr><td>Davies 1989</td><td>47</td><td>75</td><td>45</td><td>40</td><td>50</td></tr></table>
<table><caption>Table A1. *Cont.*</caption><tr><td>De Col 2010</td><td>59</td><td>100</td><td>54</td><td>50</td><td>75</td></tr><tr><td>Dekker 1993</td><td>44</td><td>100</td><td>31</td><td>40</td><td>50</td></tr><tr><td>De Oliveira 2013</td><td>56</td><td>100</td><td>46</td><td>40</td><td>100</td></tr><tr><td>Desalu 2009</td><td>47</td><td>100</td><td>46</td><td>30</td><td>50</td></tr><tr><td>Djalalinia 2011</td><td>47</td><td>100</td><td>46</td><td>20</td><td>75</td></tr><tr><td>Dodds 1979</td><td>38</td><td>50</td><td>38</td><td>43</td><td>50</td></tr><tr><td>Doll 1954</td><td>41</td><td>100</td><td>31</td><td>20</td><td>75</td></tr><tr><td>Doll 1964</td><td>44</td><td>100</td><td>38</td><td>30</td><td>50</td></tr><tr><td>Doll 1994</td><td>50</td><td>100</td><td>31</td><td>50</td><td>75</td></tr><tr><td>Doll 2004</td><td>53</td><td>100</td><td>31</td><td>50</td><td>75</td></tr><tr><td>Easton 2001</td><td>78</td><td>100</td><td>77</td><td>50</td><td>100</td></tr><tr><td>Easton 2001</td><td>61</td><td>100</td><td>54</td><td>56</td><td>75</td></tr><tr><td>Edwards 2008</td><td>63</td><td>75</td><td>46</td><td>70</td><td>75</td></tr><tr><td>Edwards 2018</td><td>66</td><td>75</td><td>46</td><td>70</td><td>100</td></tr><tr><td>Fadhil 2007</td><td>63</td><td>100</td><td>55</td><td>50</td><td>75</td></tr><tr><td>Fanello 1990</td><td>56</td><td>100</td><td>54</td><td>50</td><td>50</td></tr><tr><td>Fathi 2016</td><td>56</td><td>100</td><td>46</td><td>30</td><td>100</td></tr><tr><td>Fowler 1989</td><td>69</td><td>100</td><td>77</td><td>50</td><td>75</td></tr><tr><td>Franceschi 1986</td><td>39</td><td>50</td><td>31</td><td>50</td><td>25</td></tr><tr><td>Frank 1998</td><td>75</td><td>100</td><td>77</td><td>60</td><td>100</td></tr><tr><td>Frank 2009</td><td>63</td><td>75</td><td>54</td><td>50</td><td>100</td></tr><tr><td>Freour 2011</td><td>50</td><td>100</td><td>38</td><td>30</td><td>100</td></tr><tr><td>Garfinkel 1976</td><td>27</td><td>50</td><td>23</td><td>20</td><td>25</td></tr><tr><td>Grossman 1999</td><td>56</td><td>100</td><td>46</td><td>40</td><td>75</td></tr><tr><td>Gunes 2005</td><td>60</td><td>100</td><td>46</td><td>50</td><td>100</td></tr><tr><td>Gupta 2013</td><td>50</td><td>100</td><td>46</td><td>30</td><td>75</td></tr><tr><td>Hallett 1983</td><td>28</td><td>75</td><td>10</td><td>30</td><td>50</td></tr><tr><td>Hamadeh 1999</td><td>53</td><td>100</td><td>38</td><td>40</td><td>75</td></tr><tr><td>Han Zao Li 2008</td><td>56</td><td>100</td><td>46</td><td>40</td><td>100</td></tr><tr><td>Hay 1976</td><td>41</td><td>100</td><td>15</td><td>40</td><td>75</td></tr><tr><td>Hay 1998</td><td>53</td><td>75</td><td>31</td><td>60</td><td>75</td></tr><tr><td>Heloma 1998</td><td>56</td><td>100</td><td>46</td><td>40</td><td>75</td></tr><tr><td>Hensrud 1993</td><td>53</td><td>100</td><td>38</td><td>50</td><td>75</td></tr><tr><td>Hepburn 2000</td><td>59</td><td>100</td><td>62</td><td>40</td><td>75</td></tr><tr><td>Heponiemi 2008</td><td>59</td><td>100</td><td>46</td><td>40</td><td>100</td></tr><tr><td>Hidalgo 2016</td><td>56</td><td>100</td><td>46</td><td>40</td><td>75</td></tr><tr><td>Hill 1997</td><td>50</td><td>100</td><td>54</td><td>30</td><td>50</td></tr><tr><td>Hodgetts 2004</td><td>56</td><td>100</td><td>38</td><td>50</td><td>100</td></tr><tr><td>Hoseainrezae 2013</td><td>44</td><td>100</td><td>38</td><td>30</td><td>50</td></tr><tr><td>Huang 2013</td><td>63</td><td>100</td><td>46</td><td>50</td><td>100</td></tr><tr><td>Hughes 1991</td><td>63</td><td>100</td><td>64</td><td>40</td><td>75</td></tr><tr><td>Hughes 1992</td><td>63</td><td>75</td><td>69</td><td>40</td><td>75</td></tr></table>
<table><caption>Table A1. *Cont.*</caption><tr><td>Hughes 1999</td><td>50</td><td>100</td><td>46</td><td>20</td><td>100</td></tr><tr><td>Hung 2013</td><td>59</td><td>100</td><td>46</td><td>50</td><td>100</td></tr><tr><td>Hussain 1993</td><td>41</td><td>100</td><td>38</td><td>30</td><td>25</td></tr><tr><td>Içli 1992</td><td>34</td><td>100</td><td>31</td><td>20</td><td>25</td></tr><tr><td>Innos 2002</td><td>52</td><td>100</td><td>38</td><td>44</td><td>75</td></tr><tr><td>Jacot Sadowski 2009</td><td>73</td><td>100</td><td>82</td><td>50</td><td>75</td></tr><tr><td>Jiang 2007</td><td>63</td><td>100</td><td>69</td><td>50</td><td>50</td></tr><tr><td>Jiménez-Ruiz 2015</td><td>56</td><td>100</td><td>38</td><td>40</td><td>100</td></tr><tr><td>Jingi 2015</td><td>47</td><td>100</td><td>38</td><td>30</td><td>75</td></tr><tr><td>John 2003</td><td>41</td><td>100</td><td>31</td><td>10</td><td>75</td></tr><tr><td>Joossens 1987</td><td>38</td><td>75</td><td>31</td><td>40</td><td>25</td></tr><tr><td>Josseran 2000</td><td>47</td><td>100</td><td>46</td><td>10</td><td>100</td></tr><tr><td>Josseran 2005</td><td>59</td><td>100</td><td>46</td><td>40</td><td>100</td></tr><tr><td>Julião 2013</td><td>53</td><td>100</td><td>38</td><td>40</td><td>100</td></tr><tr><td>Kaetsu 2002</td><td>63</td><td>100</td><td>45</td><td>70</td><td>75</td></tr><tr><td>Kaetsu 2002</td><td>78</td><td>100</td><td>77</td><td>60</td><td>75</td></tr><tr><td>Kai 2008</td><td>59</td><td>100</td><td>69</td><td>30</td><td>75</td></tr><tr><td>Kaneita 2010</td><td>78</td><td>100</td><td>77</td><td>60</td><td>100</td></tr><tr><td>Kawahara 2000</td><td>70</td><td>100</td><td>64</td><td>50</td><td>100</td></tr><tr><td>Kawakami 1997</td><td>48</td><td>75</td><td>45</td><td>22</td><td>75</td></tr><tr><td>Kawane 1993</td><td>50</td><td>0</td><td>NA</td><td>NA</td><td>NA</td></tr><tr><td>Kono 1995</td><td>78</td><td>100</td><td>85</td><td>60</td><td>100</td></tr><tr><td>Kotz 2007</td><td>78</td><td>100</td><td>77</td><td>60</td><td>100</td></tr><tr><td>Lam 2011</td><td>88</td><td>100</td><td>92</td><td>70</td><td>100</td></tr><tr><td>La Vecchia 2000</td><td>20</td><td>100</td><td>15</td><td>20</td><td>NA</td></tr><tr><td>Lefcoe 1970</td><td>52</td><td>100</td><td>55</td><td>22</td><td>75</td></tr><tr><td>Legnini 1987</td><td>50</td><td>100</td><td>46</td><td>30</td><td>75</td></tr><tr><td>Lindfors 2009</td><td>66</td><td>100</td><td>69</td><td>40</td><td>100</td></tr><tr><td>Linn 1986</td><td>56</td><td>100</td><td>54</td><td>50</td><td>50</td></tr><tr><td>Lipp 1972</td><td>44</td><td>100</td><td>31</td><td>20</td><td>100</td></tr><tr><td>Lipp 1972</td><td>31</td><td>75</td><td>15</td><td>20</td><td>75</td></tr><tr><td>Magee 2017</td><td>63</td><td>100</td><td>62</td><td>30</td><td>100</td></tr><tr><td>Malik 2010</td><td>47</td><td>100</td><td>46</td><td>30</td><td>50</td></tr><tr><td>Manson 2000</td><td>63</td><td>100</td><td>62</td><td>40</td><td>100</td></tr><tr><td>Mappin-Kasirer 2020</td><td>63</td><td>100</td><td>62</td><td>50</td><td>75</td></tr><tr><td>Marakoğlu 2006</td><td>47</td><td>100</td><td>38</td><td>30</td><td>75</td></tr><tr><td>Márk 1998</td><td>53</td><td>100</td><td>46</td><td>30</td><td>100</td></tr><tr><td>Mathavan 2009</td><td>63</td><td>100</td><td>62</td><td>40</td><td>75</td></tr><tr><td>McAuliffe 1984</td><td>41</td><td>100</td><td>31</td><td>30</td><td>50</td></tr><tr><td>McEwen 2001</td><td>56</td><td>100</td><td>46</td><td>50</td><td>75</td></tr><tr><td>McGrady 2007</td><td>63</td><td>100</td><td>46</td><td>50</td><td>100</td></tr><tr><td>Mejia 2011</td><td>54</td><td>100</td><td>50</td><td>33</td><td>75</td></tr></table>
<table><caption>Table A1. *Cont.*</caption><tr><td>Merrill 2006</td><td>56</td><td>100</td><td>62</td><td>20</td><td>100</td></tr><tr><td>Meshefedjian 2010</td><td>59</td><td>100</td><td>54</td><td>40</td><td>100</td></tr><tr><td>Mikalauskas 2012</td><td>63</td><td>100</td><td>54</td><td>50</td><td>100</td></tr><tr><td>Misra 2004</td><td>63</td><td>100</td><td>62</td><td>50</td><td>75</td></tr><tr><td>Miwa 1995</td><td>50</td><td>100</td><td>46</td><td>30</td><td>75</td></tr><tr><td>Mohan 2006</td><td>50</td><td>100</td><td>46</td><td>40</td><td>50</td></tr><tr><td>Mohseni-Bandpei 2011</td><td>63</td><td>100</td><td>62</td><td>30</td><td>100</td></tr><tr><td>Moreno 2006</td><td>24</td><td>100</td><td>15</td><td>30</td><td>25</td></tr><tr><td>Mostafa 2017</td><td>63</td><td>100</td><td>62</td><td>40</td><td>100</td></tr><tr><td>Movsisyan 2019</td><td>56</td><td>100</td><td>62</td><td>40</td><td>50</td></tr><tr><td>Mubeen 2008</td><td>59</td><td>100</td><td>46</td><td>40</td><td>100</td></tr><tr><td>Naji 2006</td><td>34</td><td>100</td><td>15</td><td>30</td><td>50</td></tr><tr><td>Nakládalová 2005</td><td>50</td><td>100</td><td>38</td><td>40</td><td>50</td></tr><tr><td>Nardini 1998</td><td>53</td><td>100</td><td>54</td><td>30</td><td>50</td></tr><tr><td>Nawaz 2007</td><td>56</td><td>100</td><td>62</td><td>40</td><td>50</td></tr><tr><td>Nawaz 2008</td><td>44</td><td>100</td><td>31</td><td>30</td><td>50</td></tr><tr><td>Ndiaye 2001</td><td>56</td><td>100</td><td>54</td><td>50</td><td>50</td></tr><tr><td>Nelson 1994</td><td>65</td><td>75</td><td>77</td><td>22</td><td>100</td></tr><tr><td>Ng 2007</td><td>61</td><td>100</td><td>62</td><td>56</td><td>50</td></tr><tr><td>Nollen 2004</td><td>53</td><td>100</td><td>54</td><td>30</td><td>75</td></tr><tr><td>Nutbeam 1990</td><td>53</td><td>100</td><td>46</td><td>40</td><td>50</td></tr><tr><td>Obeidat 2017</td><td>66</td><td>100</td><td>54</td><td>50</td><td>100</td></tr><tr><td>Öztürk 2012</td><td>59</td><td>100</td><td>69</td><td>50</td><td>25</td></tr><tr><td>O'Cathail 2013</td><td>63</td><td>100</td><td>62</td><td>40</td><td>100</td></tr><tr><td>Ohida 2001</td><td>63</td><td>100</td><td>54</td><td>40</td><td>100</td></tr><tr><td>O'Keeffe 2019</td><td>75</td><td>100</td><td>69</td><td>60</td><td>100</td></tr><tr><td>Pärna 2005 A</td><td>69</td><td>100</td><td>69</td><td>40</td><td>100</td></tr><tr><td>Pärna 2005 B</td><td>66</td><td>100</td><td>62</td><td>40</td><td>100</td></tr><tr><td>Pärna 2017</td><td>59</td><td>100</td><td>46</td><td>40</td><td>100</td></tr><tr><td>Perrin 2006</td><td>63</td><td>100</td><td>62</td><td>40</td><td>100</td></tr><tr><td>Peykari 2010</td><td>59</td><td>100</td><td>46</td><td>40</td><td>100</td></tr><tr><td>Phillips 1968</td><td>41</td><td>100</td><td>31</td><td>30</td><td>50</td></tr><tr><td>Pillay 2020</td><td>47</td><td>50</td><td>31</td><td>50</td><td>50</td></tr><tr><td>Pipe 2009</td><td>59</td><td>100</td><td>54</td><td>30</td><td>100</td></tr><tr><td>Piryani 2004</td><td>34</td><td>100</td><td>15</td><td>30</td><td>50</td></tr><tr><td>Pizzo 2003</td><td>47</td><td>100</td><td>42</td><td>30</td><td>50</td></tr><tr><td>Poanta 2006</td><td>73</td><td>75</td><td>77</td><td>50</td><td>100</td></tr><tr><td>Pöld 2017</td><td>72</td><td>100</td><td>69</td><td>50</td><td>100</td></tr><tr><td>Pöld 2020</td><td>94</td><td>100</td><td>92</td><td>90</td><td>100</td></tr><tr><td>Polyzos 1995</td><td>38</td><td>50</td><td>38</td><td>40</td><td>25</td></tr><tr><td>Power 1999</td><td>66</td><td>100</td><td>77</td><td>40</td><td>75</td></tr></table>
<table><caption>Table A1. *Cont.*</caption><tr><td>Ramachandran 2008</td><td>70</td><td>75</td><td>73</td><td>50</td><td>75</td></tr><tr><td>Ranchal 2018</td><td>74</td><td>100</td><td>77</td><td>56</td><td>100</td></tr><tr><td>Rankin 1975</td><td>44</td><td>100</td><td>8</td><td>50</td><td>75</td></tr><tr><td>Ravara 2014</td><td>55</td><td>100</td><td>31</td><td>60</td><td>75</td></tr><tr><td>Reile 2018</td><td>74</td><td>100</td><td>46</td><td>58</td><td>100</td></tr><tr><td>Roche 1995</td><td>66</td><td>100</td><td>62</td><td>60</td><td>75</td></tr><tr><td>Roche 1996</td><td>69</td><td>100</td><td>77</td><td>60</td><td>50</td></tr><tr><td>Rurik 2008</td><td>47</td><td>100</td><td>31</td><td>40</td><td>75</td></tr><tr><td>Rurik 2014</td><td>41</td><td>100</td><td>31</td><td>30</td><td>50</td></tr><tr><td>Sachs 1983</td><td>44</td><td>50</td><td>67</td><td>44</td><td>0</td></tr><tr><td>Saeed 1991</td><td>53</td><td>75</td><td>38</td><td>50</td><td>75</td></tr><tr><td>Saeys 2014</td><td>81</td><td>100</td><td>77</td><td>70</td><td>100</td></tr><tr><td>Salgado 2014</td><td>72</td><td>75</td><td>69</td><td>80</td><td>100</td></tr><tr><td>Samuels 1997</td><td>50</td><td>75</td><td>23</td><td>50</td><td>100</td></tr><tr><td>Schnoll 2006</td><td>59</td><td>100</td><td>62</td><td>50</td><td>50</td></tr><tr><td>Scott 1992</td><td>41</td><td>100</td><td>23</td><td>30</td><td>75</td></tr><tr><td>Sebo 2007</td><td>65</td><td>100</td><td>62</td><td>44</td><td>100</td></tr><tr><td>Seller 1983</td><td>42</td><td>50</td><td>44</td><td>50</td><td>25</td></tr><tr><td>Senior 1982</td><td>56</td><td>100</td><td>62</td><td>30</td><td>75</td></tr><tr><td>Sharma 1988</td><td>24</td><td>50</td><td>15</td><td>17</td><td>100</td></tr><tr><td>Shkedy 2013</td><td>59</td><td>100</td><td>36</td><td>44</td><td>100</td></tr><tr><td>Shi 2010</td><td>61</td><td>100</td><td>67</td><td>30</td><td>100</td></tr><tr><td>Shin 2012</td><td>72</td><td>100</td><td>77</td><td>50</td><td>100</td></tr><tr><td>Shishani 2008</td><td>75</td><td>100</td><td>85</td><td>40</td><td>100</td></tr><tr><td>Shishani 2011</td><td>75</td><td>75</td><td>85</td><td>60</td><td>75</td></tr><tr><td>Siddiqui 2001</td><td>50</td><td>100</td><td>46</td><td>30</td><td>75</td></tr><tr><td>Singh 1981</td><td>50</td><td>100</td><td>38</td><td>30</td><td>75</td></tr><tr><td>Smith 2006</td><td>67</td><td>100</td><td>64</td><td>50</td><td>75</td></tr><tr><td>Smith 2007</td><td>50</td><td>67</td><td>50</td><td>33</td><td>NA</td></tr><tr><td>Sotiropoulos 2007</td><td>70</td><td>100</td><td>55</td><td>80</td><td>75</td></tr><tr><td>Squier 2006</td><td>63</td><td>100</td><td>54</td><td>50</td><td>100</td></tr><tr><td>Steinberg 2007</td><td>50</td><td>100</td><td>46</td><td>30</td><td>75</td></tr><tr><td>Stuyt 2009</td><td>55</td><td>75</td><td>31</td><td>56</td><td>100</td></tr><tr><td>Sundquist 1999</td><td>72</td><td>100</td><td>69</td><td>50</td><td>100</td></tr><tr><td>Svärdsudd 2002</td><td>69</td><td>100</td><td>77</td><td>50</td><td>75</td></tr><tr><td>Tapia-Conyer 1997</td><td>66</td><td>100</td><td>62</td><td>50</td><td>75</td></tr><tr><td>Tee 2007</td><td>69</td><td>100</td><td>62</td><td>60</td><td>75</td></tr><tr><td>Tessier 1996</td><td>53</td><td>100</td><td>38</td><td>30</td><td>100</td></tr><tr><td>Thankappan 2008</td><td>56</td><td>100</td><td>62</td><td>40</td><td>50</td></tr><tr><td>Thomas 1986</td><td>66</td><td>100</td><td>54</td><td>50</td><td>100</td></tr><tr><td>Thomas 1997</td><td>44</td><td>100</td><td>38</td><td>30</td><td>50</td></tr><tr><td>Tomson 2003</td><td>56</td><td>100</td><td>46</td><td>30</td><td>100</td></tr></table>
<table><caption>**Table A1. Cont.**</caption><tbody><tr><td>Tong 2010</td><td>66</td><td>100</td><td>62</td><td>40</td><td>100</td></tr><tr><td>Torre 2005</td><td>53</td><td>100</td><td>38</td><td>30</td><td>100</td></tr><tr><td>Tosun 2016</td><td>53</td><td>100</td><td>38</td><td>30</td><td>100</td></tr><tr><td>Trédaniel 1993</td><td>50</td><td>100</td><td>54</td><td>30</td><td>50</td></tr><tr><td>Ulbricht 2009</td><td>66</td><td>100</td><td>54</td><td>50</td><td>100</td></tr><tr><td>Unal 2017</td><td>63</td><td>100</td><td>62</td><td>40</td><td>75</td></tr><tr><td>Underner 2004</td><td>63</td><td>50</td><td>62</td><td>50</td><td>100</td></tr><tr><td>Underner 2006</td><td>63</td><td>75</td><td>62</td><td>50</td><td>75</td></tr><tr><td>Uysal 2007</td><td>69</td><td>75</td><td>77</td><td>60</td><td>75</td></tr><tr><td>Vanderhoek 2013</td><td>81</td><td>100</td><td>77</td><td>70</td><td>100</td></tr><tr><td>Vanphanom 2011</td><td>73</td><td>100</td><td>85</td><td>25</td><td>100</td></tr><tr><td>Varona 2005</td><td>42</td><td>100</td><td>30</td><td>57</td><td>25</td></tr><tr><td>Viegas 2007</td><td>63</td><td>75</td><td>69</td><td>38</td><td>75</td></tr><tr><td>Voigt 2009</td><td>63</td><td>75</td><td>62</td><td>56</td><td>75</td></tr><tr><td>Waalkens 1992</td><td>57</td><td>75</td><td>42</td><td>56</td><td>75</td></tr><tr><td>Wada 2007</td><td>66</td><td>100</td><td>77</td><td>40</td><td>50</td></tr><tr><td>Wada 2011</td><td>50</td><td>100</td><td>38</td><td>40</td><td>75</td></tr><tr><td>Wang 2021</td><td>59</td><td>75</td><td>69</td><td>50</td><td>50</td></tr><tr><td>Wilf Miron 2019</td><td>59</td><td>100</td><td>54</td><td>50</td><td>50</td></tr><tr><td>Waillaing 2003</td><td>77</td><td>100</td><td>92</td><td>50</td><td>100</td></tr><tr><td>Wilson 2020</td><td>69</td><td>100</td><td>69</td><td>60</td><td>75</td></tr><tr><td>Wyshak 1980</td><td>34</td><td>50</td><td>38</td><td>22</td><td>25</td></tr><tr><td>Yaacob 1993</td><td>69</td><td>100</td><td>62</td><td>50</td><td>100</td></tr><tr><td>Yan 2008</td><td>87</td><td>100</td><td>100</td><td>67</td><td>75</td></tr><tr><td>Young 1997</td><td>56</td><td>50</td><td>NA</td><td>50</td><td>NA</td></tr><tr><td>Zabadi 2018</td><td>81</td><td>100</td><td>85</td><td>56</td><td>100</td></tr><tr><td>Zanetti 1998</td><td>47</td><td>75</td><td>54</td><td>30</td><td>50</td></tr><tr><td>Zhang 2012</td><td>56</td><td>100</td><td>69</td><td>40</td><td>25</td></tr><tr><td>Zhang 2015</td><td>70</td><td>67</td><td>NA</td><td>67</td><td>NA</td></tr><tr><td>Zhou 2010</td><td>35</td><td>75</td><td>50</td><td>60</td><td>100</td></tr><tr><td>Zinonos 2016</td><td>100</td><td>100</td><td>100</td><td>100</td><td>100</td></tr><tr><td>Zylbersztejn 2015</td><td>78</td><td>100</td><td>85</td><td>50</td><td>100</td></tr><tr><td colspan="6" style="text-align: center; font-weight: bold;">CONSORT</td></tr><tr><td></td><td>Total Score</td><td>Abstract Introduction</td><td>Methods</td><td>Results</td><td>Discussion</td><td>Other</td></tr><tr><td>Glavas 2003</td><td>73</td><td>100</td><td>59</td><td>70</td><td>67</td><td>33</td></tr><tr><td>Saadat 2012</td><td>76</td><td>100</td><td>59</td><td>80</td><td>100</td><td>33</td></tr></tbody></table>
<table><caption>**Table A2.** Methodological assessment of studies using NOS criteria. NOS for cross-sectional studies.</caption><thead><tr><th rowspan="2"></th><th colspan="5">Selection Bias</th><th>Comparability Bias</th><th>Outcome Bias</th></tr><tr><th>Sample representativeness</th><th>Sample size</th><th>Representativeness</th><th>Ascertainment of the exposure</th><th>Comparability</th><th>Assessment of the outcome</th><th>Statistical test</th></tr></thead><tbody><tr><td>Aaro 1977</td><td>+</td><td>?</td><td>?</td><td>+</td><td>+</td><td>+</td><td>?</td></tr><tr><td>Abdullah 2006</td><td>+</td><td>+</td><td>+</td><td>+</td><td>+</td><td>+</td><td>+</td></tr><tr><td>Aboyans 2009</td><td>+</td><td>+</td><td>+</td><td>+</td><td>+</td><td>+</td><td>+</td></tr><tr><td>Akvardar 2004</td><td>+</td><td>+</td><td>+</td><td>+</td><td>+</td><td>+</td><td>?</td></tr><tr><td>Al Alwan 2013</td><td>+</td><td>+</td><td>+</td><td>+</td><td>+</td><td>+</td><td>+</td></tr><tr><td>Alarjan 2015</td><td>+</td><td>+</td><td>+</td><td>+</td><td>+</td><td>+</td><td>+</td></tr><tr><td>al-Khateeb 1990</td><td>+</td><td>+</td><td>+</td><td>+</td><td>+</td><td>+</td><td>+</td></tr><tr><td>Allan 1976</td><td>+</td><td>+</td><td>+</td><td>+</td><td>+</td><td>+</td><td>+</td></tr><tr><td>Al-Lawati 2009</td><td>+</td><td>+</td><td>+</td><td>+</td><td>+</td><td>+</td><td>?</td></tr><tr><td>Al Shahrani 2021</td><td>+</td><td>+</td><td>+</td><td>+</td><td>+</td><td>+</td><td>+</td></tr><tr><td>Amara 2008</td><td>+</td><td>+</td><td>+</td><td>+</td><td>+</td><td>+</td><td>?</td></tr><tr><td>Amte 2015</td><td>+</td><td>+</td><td>+</td><td>+</td><td>+</td><td>+</td><td>+</td></tr><tr><td>An 2004</td><td>+</td><td>+</td><td>+</td><td>+</td><td>+</td><td>+</td><td>+</td></tr><tr><td>Arnetz 1988</td><td>+</td><td>+</td><td>+</td><td>+</td><td>+</td><td>+</td><td>+</td></tr><tr><td>Aryayev 2014</td><td>+</td><td>+</td><td>+</td><td>+</td><td>+</td><td>+</td><td>?</td></tr><tr><td>Baltaci 2014</td><td>+</td><td>+</td><td>+</td><td>+</td><td>+</td><td>+</td><td>+</td></tr><tr><td>Baptista 1993</td><td>+</td><td>+</td><td>+</td><td>+</td><td>+</td><td>+</td><td>+</td></tr><tr><td>Barengo 2004</td><td>+</td><td>+</td><td>+</td><td>+</td><td>+</td><td>+</td><td>+</td></tr><tr><td>Barengo 2005</td><td>+</td><td>+</td><td>+</td><td>+</td><td>+</td><td>+</td><td>+</td></tr><tr><td>Barnoya 2002</td><td>+</td><td>+</td><td>+</td><td>+</td><td>+</td><td>+</td><td>+</td></tr><tr><td>Basnyat 2000</td><td>+</td><td>+</td><td>+</td><td>+</td><td>+</td><td>+</td><td>+</td></tr><tr><td>Basu 2011</td><td>+</td><td>+</td><td>+</td><td>+</td><td>+</td><td>+</td><td>+</td></tr><tr><td>Behbehani 2004</td><td>+</td><td>+</td><td>+</td><td>+</td><td>+</td><td>+</td><td>+</td></tr><tr><td>Belkić 2007</td><td>+</td><td>+</td><td>+</td><td>+</td><td>+</td><td>+</td><td>+</td></tr></tbody></table>
<table><caption>Table A2. *Cont.*</caption><thead><tr><th rowspan="2"></th><th colspan="5">Selection Bias</th><th>Comparability Bias</th><th>Outcome Bias</th></tr><tr><th>Sample representativeness</th><th>Sample size</th><th>Representativeness</th><th>Ascertainment of the exposure</th><th>Comparability</th><th>Assessment of the outcome</th><th>Statistical test</th></tr></thead><tbody><tr><td>Belkić 2012</td><td>+</td><td>●</td><td>●</td><td>+</td><td>+</td><td>+</td><td>+</td></tr><tr><td>Bener 1993</td><td>+</td><td>●</td><td>●</td><td>●</td><td>●</td><td>●</td><td>●</td></tr><tr><td>Borgan 2014</td><td>+</td><td>+</td><td>●</td><td>?</td><td>●</td><td>+</td><td>●</td></tr><tr><td>Bortz 1992</td><td>+</td><td>●</td><td>●</td><td>●</td><td>●</td><td>●</td><td>●</td></tr><tr><td>Bostan 2015</td><td>+</td><td>●</td><td>●</td><td>+</td><td>+</td><td>+</td><td>+</td></tr><tr><td>Bourke 1972</td><td>+</td><td>●</td><td>●</td><td>?</td><td>●</td><td>+</td><td>●</td></tr><tr><td>Braun 2004</td><td>+</td><td>+</td><td>?</td><td>●</td><td>+</td><td>+</td><td>●</td></tr><tr><td>Brenner 1996</td><td>+</td><td>●</td><td>●</td><td>+</td><td>?</td><td>+</td><td>●</td></tr><tr><td>Brink 1994</td><td>+</td><td>●</td><td>●</td><td>+</td><td>+</td><td>+</td><td>●</td></tr><tr><td>Brotonsc 2005</td><td>+</td><td>+</td><td>●</td><td>?</td><td>+</td><td>+</td><td>?</td></tr><tr><td>Burgess 1970</td><td>+</td><td>●</td><td>+</td><td>●</td><td>●</td><td>+</td><td>●</td></tr><tr><td>Burgess 1978</td><td>+</td><td>●</td><td>+</td><td>●</td><td>●</td><td>+</td><td>●</td></tr><tr><td>Carlos 2020</td><td>+</td><td>●</td><td>?</td><td>+</td><td>+</td><td>+</td><td>+</td></tr><tr><td>Ceraso 2009</td><td>+</td><td>●</td><td>●</td><td>+</td><td>+</td><td>+</td><td>●</td></tr><tr><td>Chaudhry 2009</td><td>+</td><td>●</td><td>●</td><td>●</td><td>●</td><td>+</td><td>●</td></tr><tr><td>Cheng 1990</td><td>?</td><td>●</td><td>+</td><td>●</td><td>●</td><td>+</td><td>●</td></tr><tr><td>Coe 1971</td><td>+</td><td>●</td><td>●</td><td>●</td><td>●</td><td>+</td><td>●</td></tr><tr><td>Cofta 2008</td><td>+</td><td>●</td><td>●</td><td>●</td><td>+</td><td>+</td><td>●</td></tr><tr><td>Das 2013</td><td>+</td><td>?</td><td>●</td><td>?</td><td>+</td><td>+</td><td>●</td></tr><tr><td>Davies 1989</td><td>+</td><td>●</td><td>●</td><td>+</td><td>+</td><td>+</td><td>●</td></tr><tr><td>De Col 2010</td><td>+</td><td>●</td><td>●</td><td>●</td><td>+</td><td>+</td><td>●</td></tr><tr><td>Dekker 1993</td><td>+</td><td>●</td><td>●</td><td>+</td><td>●</td><td>+</td><td>●</td></tr><tr><td>De Oliveira 2013</td><td>+</td><td>●</td><td>●</td><td>+</td><td>+</td><td>+</td><td>●</td></tr><tr><td>Desalu 2009</td><td>+</td><td>+</td><td>●</td><td>?</td><td>●</td><td>+</td><td>●</td></tr></tbody></table>
<table><caption>Table A2. *Cont.*</caption><thead><tr><th rowspan="2"></th><th colspan="5">Selection Bias</th><th>Comparability Bias</th><th>Outcome Bias</th></tr><tr><th>Sample representativeness</th><th>Sample size</th><th>Representativeness</th><th>Ascertainment of the exposure</th><th>Comparability</th><th>Assessment of the outcome</th><th>Statistical test</th></tr></thead><tbody><tr><td>Djalalinia 2011</td><td>+</td><td>+</td><td>●</td><td>+</td><td>●</td><td>+</td><td>●</td></tr><tr><td>Dodds 1979</td><td>+</td><td>●</td><td>●</td><td>+</td><td>●</td><td>+</td><td>●</td></tr><tr><td>Doll 1954</td><td>+</td><td>●</td><td>●</td><td>+</td><td>●</td><td>+</td><td>●</td></tr><tr><td>Doll 1964</td><td>+</td><td>●</td><td>+</td><td>+</td><td>●</td><td>+</td><td>●</td></tr><tr><td>Doll 1994</td><td>+</td><td>●</td><td>+</td><td>+</td><td>?</td><td>+</td><td>●</td></tr><tr><td>Doll 2004</td><td>+</td><td>●</td><td>+</td><td>+</td><td>+</td><td>+</td><td>●</td></tr><tr><td>Easton 2001</td><td>+</td><td>●</td><td>+</td><td>+</td><td>+</td><td>+</td><td>+</td></tr><tr><td>Easton 2001</td><td>+</td><td>+</td><td>+</td><td>?</td><td>+</td><td>+</td><td>+</td></tr><tr><td>Edwards 2008</td><td>+</td><td>+</td><td>+</td><td>+</td><td>+</td><td>+</td><td>+</td></tr><tr><td>Edwards 2018</td><td>+</td><td>+</td><td>●</td><td>+</td><td>+</td><td>+</td><td>+</td></tr><tr><td>Fadhil 2007</td><td>+</td><td>●</td><td>+</td><td>●</td><td>+</td><td>+</td><td>+</td></tr><tr><td>Fanello 1990</td><td>+</td><td>●</td><td>+</td><td>+</td><td>+</td><td>+</td><td>+</td></tr><tr><td>Fathi 2016</td><td>+</td><td>+</td><td>●</td><td>+</td><td>+</td><td>+</td><td>+</td></tr><tr><td>Fowler 1989</td><td>+</td><td>●</td><td>●</td><td>+</td><td>?</td><td>+</td><td>+</td></tr><tr><td>Franceschi 1986</td><td>?</td><td>+</td><td>●</td><td>?</td><td>+</td><td>+</td><td>+</td></tr><tr><td>Frank 1998</td><td>+</td><td>+</td><td>+</td><td>+</td><td>+</td><td>+</td><td>+</td></tr><tr><td>Frank 2009</td><td>+</td><td>+</td><td>+</td><td>+</td><td>+</td><td>+</td><td>+</td></tr><tr><td>Freour 2011</td><td>+</td><td>●</td><td>●</td><td>+</td><td>+</td><td>+</td><td>?</td></tr><tr><td>Garfinkel 1976</td><td>+</td><td>●</td><td>●</td><td>●</td><td>●</td><td>+</td><td>●</td></tr><tr><td>Grossman 1999</td><td>?</td><td>●</td><td>+</td><td>?</td><td>+</td><td>+</td><td>●</td></tr><tr><td>Gunes 2005</td><td>+</td><td>●</td><td>●</td><td>+</td><td>+</td><td>+</td><td>+</td></tr><tr><td>Gupta 2013</td><td>+</td><td>●</td><td>●</td><td>+</td><td>+</td><td>+</td><td>●</td></tr><tr><td>Hallett 1983</td><td>+</td><td>●</td><td>●</td><td>●</td><td>●</td><td>+</td><td>●</td></tr><tr><td>Hamadeh 1999</td><td>+</td><td>●</td><td>●</td><td>+</td><td>+</td><td>+</td><td>●</td></tr></tbody></table>
<table><caption>Table A2. *Cont.*</caption><thead><tr><th rowspan="2"></th><th colspan="5">Selection Bias</th><th>Comparability Bias</th><th>Outcome Bias</th></tr><tr><th>Sample representativeness</th><th>Sample size</th><th>Representativeness</th><th>Ascertainment of the exposure</th><th>Comparability</th><th>Assessment of the outcome</th><th>Statistical test</th></tr></thead><tbody><tr><td>Han Zao Li 2008</td><td>?</td><td>●</td><td>●</td><td>●</td><td>●</td><td>●</td><td>●</td></tr><tr><td>Hay 1976</td><td>●</td><td>●</td><td>●</td><td>●</td><td>●</td><td>●</td><td>●</td></tr><tr><td>Hay 1998</td><td>●</td><td>●</td><td>●</td><td>●</td><td>●</td><td>●</td><td>●</td></tr><tr><td>Heloma 1998</td><td>●</td><td>●</td><td>●</td><td>●</td><td>●</td><td>●</td><td>●</td></tr><tr><td>Hensrud 1993</td><td>●</td><td>●</td><td>?</td><td>?</td><td>●</td><td>●</td><td>●</td></tr><tr><td>Hepburn 2000</td><td>●</td><td>●</td><td>●</td><td>●</td><td>●</td><td>●</td><td>●</td></tr><tr><td>Heponiemi 2008</td><td>●</td><td>●</td><td>●</td><td>●</td><td>●</td><td>●</td><td>?</td></tr><tr><td>Hidalgo 2016</td><td>●</td><td>●</td><td>●</td><td>●</td><td>●</td><td>●</td><td>●</td></tr><tr><td>Hill 1997</td><td>●</td><td>●</td><td>●</td><td>●</td><td>●</td><td>●</td><td>●</td></tr><tr><td>Hodgetts 2004</td><td>●</td><td>●</td><td>●</td><td>●</td><td>●</td><td>●</td><td>●</td></tr><tr><td>Hoseainrezae 2013</td><td>●</td><td>●</td><td>●</td><td>●</td><td>●</td><td>●</td><td>●</td></tr><tr><td>Huang 2013</td><td>●</td><td>●</td><td>●</td><td>●</td><td>●</td><td>●</td><td>●</td></tr><tr><td>Hughes 1991</td><td>●</td><td>●</td><td>●</td><td>●</td><td>●</td><td>●</td><td>●</td></tr><tr><td>Hughes 1992</td><td>●</td><td>●</td><td>●</td><td>●</td><td>●</td><td>●</td><td>●</td></tr><tr><td>Hughes 1999</td><td>●</td><td>●</td><td>●</td><td>●</td><td>●</td><td>●</td><td>●</td></tr><tr><td>Hung 2013</td><td>●</td><td>●</td><td>?</td><td>●</td><td>●</td><td>●</td><td>●</td></tr><tr><td>Hussain 1993</td><td>●</td><td>●</td><td>●</td><td>●</td><td>●</td><td>●</td><td>●</td></tr><tr><td>Içli 1992</td><td>●</td><td>●</td><td>●</td><td>●</td><td>●</td><td>●</td><td>●</td></tr><tr><td>Jacot Sadowski 2009</td><td>●</td><td>●</td><td>●</td><td>●</td><td>●</td><td>●</td><td>●</td></tr><tr><td>Jiang 2007</td><td>●</td><td>●</td><td>●</td><td>●</td><td>●</td><td>●</td><td>●</td></tr><tr><td>Jiménez-Ruiz 2015</td><td>?</td><td>●</td><td>●</td><td>●</td><td>●</td><td>●</td><td>?</td></tr><tr><td>Jingi 2015</td><td>●</td><td>●</td><td>●</td><td>●</td><td>●</td><td>●</td><td>●</td></tr><tr><td>John 2003</td><td>●</td><td>●</td><td>●</td><td>●</td><td>●</td><td>●</td><td>●</td></tr></tbody></table>
<table><caption>Table A2. *Cont.*</caption><thead><tr><th rowspan="2"></th><th colspan="4">Selection Bias</th><th>Comparability Bias</th><th>Outcome Bias</th></tr><tr><th>Sample representativeness</th><th>Sample size</th><th>Representativeness</th><th>Ascertainment of the exposure</th><th>Comparability</th><th>Assessment of the outcome</th><th>Statistical test</th></tr></thead><tbody><tr><td>Joossens 1987</td><td>+</td><td>●</td><td>●</td><td>+</td><td>●</td><td>+</td><td>●</td></tr><tr><td>Josseran 2000</td><td>+</td><td>●</td><td>●</td><td>+</td><td>+</td><td>+</td><td>●</td></tr><tr><td>Josseran 2005</td><td>+</td><td>●</td><td>●</td><td>+</td><td>+</td><td>+</td><td>+</td></tr><tr><td>Julião 2013</td><td>+</td><td>●</td><td>●</td><td>+</td><td>+</td><td>+</td><td>●</td></tr><tr><td>Kaetsu 2002</td><td>+</td><td>+</td><td>●</td><td>+</td><td>+</td><td>+</td><td>+</td></tr><tr><td>Kai 2008</td><td>+</td><td>●</td><td>●</td><td>+</td><td>●</td><td>+</td><td>+</td></tr><tr><td>Kaneita 2010</td><td>+</td><td>+</td><td>●</td><td>+</td><td>+</td><td>+</td><td>+</td></tr><tr><td>Kawahara 2000</td><td>+</td><td>?</td><td>●</td><td>+</td><td>+</td><td>+</td><td>+</td></tr><tr><td>Kawakami 1997</td><td>+</td><td>+</td><td>●</td><td>+</td><td>+</td><td>+</td><td>+</td></tr><tr><td>Kawane 1993</td><td>+</td><td>●</td><td>●</td><td>●</td><td>●</td><td>●</td><td>●</td></tr><tr><td>Kotz 2007</td><td>+</td><td>+</td><td>?</td><td>?</td><td>+</td><td>+</td><td>+</td></tr><tr><td>Lam 2011</td><td>+</td><td>+</td><td>+</td><td>+</td><td>+</td><td>+</td><td>+</td></tr><tr><td>La Vecchia 2000</td><td>+</td><td>●</td><td>●</td><td>+</td><td>●</td><td>+</td><td>●</td></tr><tr><td>Lefcoe 1970</td><td>+</td><td>+</td><td>●</td><td>+</td><td>?</td><td>+</td><td>+</td></tr><tr><td>Legnini 1987</td><td>+</td><td>+</td><td>●</td><td>+</td><td>●</td><td>+</td><td>●</td></tr><tr><td>Lindfors 2009</td><td>+</td><td>●</td><td>●</td><td>+</td><td>+</td><td>+</td><td>+</td></tr><tr><td>Linn 1986</td><td>+</td><td>●</td><td>●</td><td>+</td><td>+</td><td>+</td><td>●</td></tr><tr><td>Lipp 1972</td><td>+</td><td>●</td><td>●</td><td>+</td><td>●</td><td>+</td><td>●</td></tr><tr><td>Lipp 1972</td><td>+</td><td>●</td><td>●</td><td>+</td><td>●</td><td>+</td><td>●</td></tr><tr><td>Magee 2017</td><td>+</td><td>●</td><td>●</td><td>+</td><td>+</td><td>+</td><td>+</td></tr><tr><td>Malik 2010</td><td>+</td><td>●</td><td>●</td><td>+</td><td>+</td><td>+</td><td>●</td></tr><tr><td>Marakoğlu 2006</td><td>+</td><td>●</td><td>●</td><td>+</td><td>+</td><td>+</td><td>●</td></tr><tr><td>Márk 1998</td><td>+</td><td>●</td><td>●</td><td>?</td><td>●</td><td>+</td><td>●</td></tr></tbody></table>
<table><caption>Table A2. *Cont.*</caption><thead><tr><th rowspan="2"></th><th colspan="4">Selection Bias</th><th>Comparability Bias</th><th>Outcome Bias</th></tr><tr><th>Sample representativeness</th><th>Sample size</th><th>Representativeness</th><th>Ascertainment of the exposure</th><th>Comparability</th><th>Assessment of the outcome</th><th>Statistical test</th></tr></thead><tbody><tr><td>Mathavan 2009</td><td>+</td><td>●</td><td>●</td><td>●</td><td>+</td><td>+</td><td>●</td></tr><tr><td>McAuliffe 1984</td><td>+</td><td>●</td><td>●</td><td>●</td><td>●</td><td>●</td><td>●</td></tr><tr><td>McEwen</td><td>+</td><td>●</td><td>●</td><td>●</td><td>●</td><td>●</td><td>●</td></tr><tr><td>McGrady 2007</td><td>+</td><td>●</td><td>●</td><td>●</td><td>●</td><td>●</td><td>?</td></tr><tr><td>Mejia 2011</td><td>+</td><td>●</td><td>●</td><td>●</td><td>●</td><td>●</td><td>●</td></tr><tr><td>Merrill 2006</td><td>+</td><td>●</td><td>●</td><td>●</td><td>●</td><td>●</td><td>●</td></tr><tr><td>Meshefedjian 2010</td><td>+</td><td>●</td><td>●</td><td>?</td><td>●</td><td>●</td><td>●</td></tr><tr><td>Mikalauskas 2012</td><td>+</td><td>●</td><td>●</td><td>●</td><td>●</td><td>●</td><td>●</td></tr><tr><td>Misra 2004</td><td>+</td><td>●</td><td>●</td><td>●</td><td>●</td><td>●</td><td>●</td></tr><tr><td>Miwa 1995</td><td>+</td><td>●</td><td>●</td><td>●</td><td>●</td><td>●</td><td>●</td></tr><tr><td>Mohan 2006</td><td>+</td><td>●</td><td>●</td><td>●</td><td>●</td><td>●</td><td>●</td></tr><tr><td>Mohseni-Bandpei 2011</td><td>+</td><td>●</td><td>●</td><td>●</td><td>?</td><td>●</td><td>●</td></tr><tr><td>Moreno 2006</td><td>+</td><td>●</td><td>●</td><td>●</td><td>●</td><td>●</td><td>●</td></tr><tr><td>Mostafa 2017</td><td>+</td><td>●</td><td>●</td><td>?</td><td>●</td><td>●</td><td>?</td></tr><tr><td>Movsisyan 2019</td><td>+</td><td>●</td><td>?</td><td>●</td><td>●</td><td>●</td><td>●</td></tr><tr><td>Mubeen 2008</td><td>+</td><td>●</td><td>●</td><td>●</td><td>●</td><td>●</td><td>●</td></tr><tr><td>Naji 2006</td><td>+</td><td>●</td><td>●</td><td>●</td><td>●</td><td>●</td><td>●</td></tr><tr><td>Nakládalová 2005</td><td>+</td><td>●</td><td>●</td><td>●</td><td>●</td><td>●</td><td>●</td></tr><tr><td>Nardini 1998</td><td>+</td><td>●</td><td>●</td><td>●</td><td>●</td><td>●</td><td>●</td></tr><tr><td>Nawaz 2007</td><td>+</td><td>●</td><td>●</td><td>●</td><td>●</td><td>●</td><td>●</td></tr><tr><td>Nawaz 2008</td><td>+</td><td>●</td><td>●</td><td>?</td><td>●</td><td>●</td><td>●</td></tr><tr><td>Ndiaye 2001</td><td>+</td><td>●</td><td>●</td><td>●</td><td>●</td><td>●</td><td>●</td></tr><tr><td>Nelson 1994</td><td>+</td><td>●</td><td>●</td><td>●</td><td>●</td><td>●</td><td>●</td></tr></tbody></table>
<table><caption>Table A2. *Cont.*</caption><thead><tr><th rowspan="2"></th><th colspan="4">Selection Bias</th><th>Comparability Bias</th><th>Outcome Bias</th></tr><tr><th>Sample representativeness</th><th>Sample size</th><th>Representativeness</th><th>Ascertainment of the exposure</th><th>Comparability</th><th>Assessment of the outcome</th><th>Statistical test</th></tr></thead><tbody><tr><td>Ng 2007</td><td>+</td><td>●</td><td>●</td><td>+</td><td>+</td><td>+</td><td>+</td></tr><tr><td>Nollen 2004</td><td>+</td><td>●</td><td>●</td><td>+</td><td>●</td><td>+</td><td>+</td></tr><tr><td>Nutbeam 1990</td><td>?</td><td>●</td><td>●</td><td>+</td><td>●</td><td>+</td><td>●</td></tr><tr><td>Obeidat 2017</td><td>+</td><td>●</td><td>+</td><td>?</td><td>+</td><td>+</td><td>+</td></tr><tr><td>Öztürk 2012</td><td>+</td><td>●</td><td>●</td><td>●</td><td>+</td><td>+</td><td>+</td></tr><tr><td>O'Cathail 2013</td><td>+</td><td>●</td><td>●</td><td>+</td><td>+</td><td>+</td><td>+</td></tr><tr><td>Ohida 2001</td><td>+</td><td>+</td><td>●</td><td>+</td><td>+</td><td>+</td><td>+</td></tr><tr><td>O'Keeffe 2019</td><td>+</td><td>+</td><td>●</td><td>+</td><td>+</td><td>+</td><td>+</td></tr><tr><td>Pärna 2005 A</td><td>+</td><td>+</td><td>●</td><td>+</td><td>+</td><td>+</td><td>+</td></tr><tr><td>Pärna 2005 B</td><td>+</td><td>●</td><td>●</td><td>+</td><td>+</td><td>+</td><td>+</td></tr><tr><td>Pärna 2017</td><td>+</td><td>●</td><td>●</td><td>+</td><td>+</td><td>+</td><td>+</td></tr><tr><td>Perrin 2006</td><td>+</td><td>●</td><td>●</td><td>+</td><td>+</td><td>+</td><td>+</td></tr><tr><td>Peykari 2010</td><td>+</td><td>●</td><td>●</td><td>+</td><td>+</td><td>+</td><td>+</td></tr><tr><td>Phillips 1968</td><td>+</td><td>●</td><td>●</td><td>+</td><td>●</td><td>+</td><td>●</td></tr><tr><td>Pillay 2020</td><td>+</td><td>●</td><td>●</td><td>+</td><td>●</td><td>+</td><td>+</td></tr><tr><td>Pipe 2009</td><td>+</td><td>●</td><td>●</td><td>+</td><td>?</td><td>+</td><td>?</td></tr><tr><td>Piryani 2004</td><td>+</td><td>●</td><td>●</td><td>●</td><td>●</td><td>+</td><td>●</td></tr><tr><td>Pizzo 2003</td><td>+</td><td>●</td><td>●</td><td>+</td><td>+</td><td>+</td><td>+</td></tr><tr><td>Poanta 2006</td><td>+</td><td>+</td><td>●</td><td>+</td><td>+</td><td>+</td><td>+</td></tr><tr><td>Pöld 2017</td><td>+</td><td>+</td><td>●</td><td>+</td><td>+</td><td>+</td><td>+</td></tr><tr><td>Pöld 2020</td><td>+</td><td>+</td><td>+</td><td>+</td><td>+</td><td>+</td><td>+</td></tr><tr><td>Polyzos 1995</td><td>+</td><td>●</td><td>●</td><td>+</td><td>●</td><td>+</td><td>●</td></tr><tr><td>Power 1999</td><td>+</td><td>●</td><td>●</td><td>+</td><td>+</td><td>+</td><td>+</td></tr></tbody></table>
<table><caption>Table A2. *Cont.*</caption><thead><tr><th rowspan="2"></th><th colspan="5">Selection Bias</th><th>Comparability Bias</th><th>Outcome Bias</th></tr><tr><th>Sample representativeness</th><th>Sample size</th><th>Representativeness</th><th>Ascertainment of the exposure</th><th>Comparability</th><th>Assessment of the outcome</th><th>Statistical test</th></tr></thead><tbody><tr><td>Ramachandran 2008</td><td>+</td><td>+</td><td>●</td><td>+</td><td>+</td><td>+</td><td>+</td></tr><tr><td>Ranchal 2018</td><td>+</td><td>+</td><td>●</td><td>+</td><td>+</td><td>+</td><td>+</td></tr><tr><td>Rankin 1975</td><td>+</td><td>●</td><td>+</td><td>●</td><td>●</td><td>+</td><td>●</td></tr><tr><td>Ravara 2014</td><td>+</td><td>●</td><td>●</td><td>●</td><td>+</td><td>+</td><td>+</td></tr><tr><td>Reile 2018</td><td>+</td><td>●</td><td>+</td><td>●</td><td>●</td><td>+</td><td>?</td></tr><tr><td>Roche 1995</td><td>+</td><td>●</td><td>●</td><td>+</td><td>●</td><td>+</td><td>+</td></tr><tr><td>Roche 1996</td><td>+</td><td>●</td><td>●</td><td>+</td><td>+</td><td>+</td><td>+</td></tr><tr><td>Sachs 1983</td><td>+</td><td>●</td><td>●</td><td>+</td><td>?</td><td>+</td><td>●</td></tr><tr><td>Saeed 1991</td><td>+</td><td>●</td><td>+</td><td>●</td><td>●</td><td>+</td><td>+</td></tr><tr><td>Saeys 2014</td><td>+</td><td>●</td><td>●</td><td>+</td><td>+</td><td>+</td><td>+</td></tr><tr><td>Salgado 2014</td><td>+</td><td>●</td><td>+</td><td>?</td><td>+</td><td>+</td><td>+</td></tr><tr><td>Samuels 1997</td><td>●</td><td>●</td><td>●</td><td>●</td><td>+</td><td>+</td><td>?</td></tr><tr><td>Schnoll 2006</td><td>+</td><td>●</td><td>●</td><td>+</td><td>●</td><td>+</td><td>+</td></tr><tr><td>Scott 1992</td><td>+</td><td>●</td><td>●</td><td>+</td><td>●</td><td>+</td><td>●</td></tr><tr><td>Sebo 2007</td><td>+</td><td>●</td><td>●</td><td>+</td><td>+</td><td>+</td><td>+</td></tr><tr><td>Seiler 1983</td><td>+</td><td>●</td><td>●</td><td>+</td><td>?</td><td>+</td><td>●</td></tr><tr><td>Senior 1982</td><td>+</td><td>●</td><td>●</td><td>+</td><td>+</td><td>+</td><td>+</td></tr><tr><td>Sharma 1988</td><td>+</td><td>●</td><td>●</td><td>●</td><td>+</td><td>+</td><td>●</td></tr><tr><td>Shkedy 2013</td><td>+</td><td>●</td><td>●</td><td>?</td><td>+</td><td>+</td><td>+</td></tr><tr><td>Shi 2010</td><td>+</td><td>●</td><td>●</td><td>+</td><td>+</td><td>+</td><td>+</td></tr><tr><td>Shin 2012</td><td>+</td><td>●</td><td>●</td><td>+</td><td>+</td><td>+</td><td>+</td></tr><tr><td>Shishani 2008</td><td>+</td><td>●</td><td>●</td><td>+</td><td>+</td><td>+</td><td>+</td></tr><tr><td>Shishani 2011</td><td>+</td><td>+</td><td>●</td><td>+</td><td>+</td><td>+</td><td>+</td></tr></tbody></table>
<table><caption>Table A2. *Cont.*</caption><thead><tr><th rowspan="2"></th><th colspan="4">Selection Bias</th><th>Comparability Bias</th><th>Outcome Bias</th></tr><tr><th>Sample representativeness</th><th>Sample size</th><th>Representativeness</th><th>Ascertainment of the exposure</th><th>Comparability</th><th>Assessment of the outcome</th><th>Statistical test</th></tr></thead><tbody><tr><td>Siddiqui 2001</td><td>+</td><td>●</td><td>●</td><td>+</td><td>●</td><td>+</td><td>+</td></tr><tr><td>Singh 1981</td><td>+</td><td>●</td><td>●</td><td>+</td><td>●</td><td>+</td><td>●</td></tr><tr><td>Smith 2006</td><td>+</td><td>●</td><td>●</td><td>●</td><td>●</td><td>+</td><td>+</td></tr><tr><td>Smith 2007</td><td>+</td><td>●</td><td>●</td><td>●</td><td>●</td><td>+</td><td>●</td></tr><tr><td>Sotiropoulos 2007</td><td>+</td><td>●</td><td>●</td><td>?</td><td>●</td><td>●</td><td>●</td></tr><tr><td>Squier 2006</td><td>+</td><td>●</td><td>●</td><td>●</td><td>●</td><td>●</td><td>●</td></tr><tr><td>Steinberg 2007</td><td>+</td><td>●</td><td>●</td><td>●</td><td>●</td><td>●</td><td>●</td></tr><tr><td>Stuyt 2009</td><td>+</td><td>●</td><td>●</td><td>●</td><td>?</td><td>●</td><td>●</td></tr><tr><td>Sundquist 1999</td><td>+</td><td>●</td><td>●</td><td>●</td><td>●</td><td>●</td><td>●</td></tr><tr><td>Tapia-Conyer 1997</td><td>+</td><td>●</td><td>●</td><td>●</td><td>●</td><td>●</td><td>●</td></tr><tr><td>Tee 2007</td><td>+</td><td>●</td><td>●</td><td>●</td><td>●</td><td>●</td><td>●</td></tr><tr><td>Tessier 1996</td><td>+</td><td>●</td><td>●</td><td>●</td><td>●</td><td>●</td><td>●</td></tr><tr><td>Thankappan 2008</td><td>+</td><td>●</td><td>●</td><td>●</td><td>●</td><td>●</td><td>●</td></tr><tr><td>Thomas 1986</td><td>+</td><td>●</td><td>●</td><td>●</td><td>●</td><td>●</td><td>●</td></tr><tr><td>Tomson 2003</td><td>+</td><td>●</td><td>●</td><td>●</td><td>●</td><td>●</td><td>●</td></tr><tr><td>Tong 2010</td><td>+</td><td>●</td><td>●</td><td>●</td><td>●</td><td>●</td><td>●</td></tr><tr><td>Tosun 2016</td><td>+</td><td>●</td><td>●</td><td>●</td><td>●</td><td>●</td><td>●</td></tr><tr><td>Trédaniel 1993</td><td>+</td><td>●</td><td>●</td><td>●</td><td>●</td><td>●</td><td>●</td></tr><tr><td>Ulbricht 2009</td><td>+</td><td>●</td><td>●</td><td>●</td><td>●</td><td>●</td><td>●</td></tr><tr><td>Underner 2004</td><td>+</td><td>●</td><td>●</td><td>●</td><td>●</td><td>●</td><td>●</td></tr><tr><td>Underner 2006</td><td>+</td><td>●</td><td>●</td><td>●</td><td>●</td><td>●</td><td>●</td></tr><tr><td>Uysal 2007</td><td>?</td><td>●</td><td>●</td><td>●</td><td>●</td><td>●</td><td>●</td></tr><tr><td>Vanderhoek 2013</td><td>+</td><td>●</td><td>●</td><td>●</td><td>●</td><td>●</td><td>●</td></tr></tbody></table>
<table><caption>Table A2. *Cont.*</caption><thead><tr><th rowspan="2"></th><th colspan="5">Selection Bias</th><th>Comparability Bias</th><th>Outcome Bias</th></tr><tr><th>Sample representativeness</th><th>Sample size</th><th>Representativeness</th><th>Ascertainment of the exposure</th><th>Comparability</th><th>Assessment of the outcome</th><th>Statistical test</th></tr></thead><tbody><tr><td>Vanphanom 2011</td><td>+</td><td>+</td><td>+</td><td>+</td><td>+</td><td>+</td><td>?</td></tr><tr><td>Varona 2005</td><td>+</td><td>-</td><td>-</td><td>-</td><td>-</td><td>+</td><td>+</td></tr><tr><td>Viegas 2007</td><td>+</td><td>+</td><td>-</td><td>+</td><td>+</td><td>+</td><td>+</td></tr><tr><td>Voigt 2009</td><td>+</td><td>-</td><td>-</td><td>+</td><td>+</td><td>+</td><td>+</td></tr><tr><td>Waalkens 1992</td><td>+</td><td>?</td><td>-</td><td>-</td><td>+</td><td>+</td><td>+</td></tr><tr><td>Wada 2007</td><td>+</td><td>-</td><td>-</td><td>+</td><td>+</td><td>+</td><td>+</td></tr><tr><td>Wada 2011</td><td>+</td><td>-</td><td>-</td><td>+</td><td>+</td><td>+</td><td>-</td></tr><tr><td>Wang 2021</td><td>+</td><td>+</td><td>-</td><td>?</td><td>?</td><td>+</td><td>+</td></tr><tr><td>Wilf Miron 2019</td><td>+</td><td>-</td><td>-</td><td>+</td><td>+</td><td>+</td><td>?</td></tr><tr><td>Willaing 2003</td><td>+</td><td>-</td><td>-</td><td>+</td><td>+</td><td>+</td><td>+</td></tr><tr><td>Wilson 2020</td><td>+</td><td>-</td><td>?</td><td>+</td><td>+</td><td>+</td><td>+</td></tr><tr><td>Wyshak 1980</td><td>+</td><td>+</td><td>?</td><td>-</td><td>-</td><td>+</td><td>-</td></tr><tr><td>Yaacob 1993</td><td>+</td><td>+</td><td>+</td><td>+</td><td>+</td><td>+</td><td>-</td></tr><tr><td>Yan 2008</td><td>+</td><td>+</td><td>+</td><td>+</td><td>+</td><td>+</td><td>+</td></tr><tr><td>Young 1997</td><td>-</td><td>+</td><td>-</td><td>-</td><td>+</td><td>+</td><td>-</td></tr><tr><td>Zabadi 2018</td><td>+</td><td>+</td><td>+</td><td>?</td><td>+</td><td>+</td><td>+</td></tr><tr><td>Zanetti 1998</td><td>+</td><td>-</td><td>-</td><td>+</td><td>+</td><td>+</td><td>-</td></tr><tr><td>Zhang 2012</td><td>+</td><td>-</td><td>-</td><td>+</td><td>-</td><td>+</td><td>+</td></tr><tr><td>Zhang 2015</td><td>+</td><td>+</td><td>-</td><td>-</td><td>-</td><td>+</td><td>-</td></tr><tr><td>Zhou 2010</td><td>+</td><td>-</td><td>-</td><td>+</td><td>+</td><td>+</td><td>+</td></tr><tr><td>Zinonos 2016</td><td>+</td><td>-</td><td>?</td><td>+</td><td>+</td><td>+</td><td>+</td></tr><tr><td>Zylbersztejn 2015</td><td>+</td><td>?</td><td>-</td><td>+</td><td>+</td><td>+</td><td>+</td></tr></tbody></table>
Appendix B

<table><caption>Table A3. NOS for cohort studies.</caption><thead><tr><th rowspan="2"></th><th colspan="4">Selection Bias</th><th>Comparability Bias</th><th>Outcome Bias</th></tr><tr><th>Representativeness of the exposed</th><th>Selection of the non-exposed</th><th>Ascertainment of the exposure</th><th>Demonstration that outcome of interest was not present at start of study</th><th>Comparability</th><th>Assessment of the outcome</th></tr></thead><tbody><tr><td>Cao 2011</td><td>+</td><td>+</td><td>●</td><td>+</td><td>+</td><td>+</td></tr><tr><td>Innos 2002</td><td>+</td><td>+</td><td>+</td><td>+</td><td>+</td><td>+</td></tr><tr><td>Kaetsu 2002</td><td>+</td><td>+</td><td>●</td><td>●</td><td>+</td><td>+</td></tr><tr><td>Kono 1985</td><td>+</td><td>+</td><td>+</td><td>+</td><td>+</td><td>+</td></tr><tr><td>Manson 2000</td><td>+</td><td>+</td><td>●</td><td>+</td><td>+</td><td>+</td></tr><tr><td>Mappin-Kasirer 2020</td><td>+</td><td>+</td><td>?</td><td>+</td><td>+</td><td>+</td></tr><tr><td>Rurik 2008</td><td>+</td><td>+</td><td>●</td><td>+</td><td>+</td><td>+</td></tr><tr><td>Rurik 2014</td><td>+</td><td>+</td><td>●</td><td>+</td><td>+</td><td>+</td></tr><tr><td>Svärdsudd 2002</td><td>+</td><td>+</td><td>●</td><td>+</td><td>+</td><td>+</td></tr><tr><td>Thomas 1997</td><td>+</td><td>+</td><td>●</td><td>●</td><td>+</td><td>+</td></tr><tr><td>Torre 2005</td><td>+</td><td>+</td><td>●</td><td>+</td><td>+</td><td>+</td></tr><tr><td>Unal 2017</td><td>+</td><td>+</td><td>+</td><td>●</td><td>+</td><td>+</td></tr></tbody></table>
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