Review

Why Review Articles on the
Health Effects of Passive Smoking
Reach Different Conclusions
Deborah E. Barnes, MPH; Lisa A. Bero, PhD

Objective.—To determine whether the conclusions of review articles on thehealth effects of passive smoking are associated with article quality, the affiliationsof their authors, or other article characteristics.
Data Sources.—Review articles published from 1980 to 1995 were identified
through electronic searches of MEDLINE and EMBASE and from a database of
symposium proceedings on passive smoking.
Article Selection.—An article was included if its stated or implied purpose wasto review the scientific evidence that passive smoking is associated with 1 or more
health outcomes. Articles were excluded if they did not focus specifically on thehealth effects of passive smoking or if they were not written in English.
Data Extraction.—Review article quality was evaluated by 2 independent
assessors who were trained, followed a written protocol, had no disclosed conflictsof interest, and were blinded to all study hypotheses and identifying characteristics
of articles. Article conclusions were categorized by the 2 assessors and by one of
the authors. Author affiliation was classified as either tobacco industry affiliated ornot, based on whether the authors were known to have received funding from orparticipated in activities sponsored by the tobacco industry. Other article characteristics were classified by one of the authors using predefined criteria.
Data Synthesis.—A total of 106 reviews were identified. Overall, 37% (39/106)
of reviews concluded that passive smoking is not harmful to health; 74% (29/39)
of these were written by authors with tobacco industry affiliations. In multiple logistic regression analyses controlling for article quality, peer review status, article topic,
and year of publication, the only factor associated with concluding that passive
smoking is not harmful was whether an author was affiliated with the tobacco industry (odds ratio, 88.4; 95% confidence interval, 16.4-476.5; P,.001).
Conclusions.—The conclusions of review articles are strongly associated withthe affiliations of their authors. Authors of review articles should disclose potential
financial conflicts of interest, and readers of review articles should consider authors’affiliations when deciding how to judge an article’s conclusions.
JAMA. 1998;279:1566-1570

THE US Environmental Protection
Agency (EPA),1 the US Surgeon General,2 the National Research Council/
From the Department of Public Health Biology andEpidemiology, School of Public Health, University ofCalifornia, Berkeley (Ms Barnes), and the Institute for
Health Policy Studies, School of Medicine, and the Department of Clinical Pharmacy, School of Pharmacy,
University of California, San Francisco (Dr Bero). Ms
Barnes was a research associate at the Institute for
Health Policy Studies, University of California, San Francisco, during the time this study was conducted.
Dr Bero has received or currently receives research
grants from the National Cancer Institute, American
Cancer Society, Robert Wood Johnson Foundation, andCalifornia Tobacco-Related Disease Research Program. Both authors also receive annual royalty payments
for a book they coauthored (The Cigarette Papers, published by University of California Press in 1996).
Reprints: Lisa A. Bero, PhD, Institute for Health Policy
Studies, 1388 Sutter St, 11th Floor, San Francisco, CA
94109 (e-mail: bero@cardio.ucsf.edu).

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JAMA, May 20, 1998—Vol 279, No. 19

National Academy of Sciences,3 and theInternational Agency for Research on Cancer4 have all reviewed the scientific evidence regarding the health effects of exposure to environmental tobacco smoke,and they have all concluded that passive
smoking increases the risk of diseases suchas lung cancer in adults and respiratory disorders in children. Several more recent reviews have found that passive smoking is
also associated with an increased risk ofheart disease5,6 and with sudden infant
death syndrome.7 However, many review articles published in the scientific literature have concluded that passive smoking is not harmful to health.8 Given that aclinician might rely on a single review article to provide an accurate and up-todate overview on a topic of interest, it issomewhat disconcerting that not all published review articles are reaching thesame conclusion about the health effectsof passive smoking, particularly when
there is consensus in the scientific community that passive smoking is harmful.
The goal of this study was to identify factors that might explain why review articles on the health effects of passive smoking are reaching different conclusions.
Several interrelated factors may influence the conclusions of review articles.
First, the conclusions of review articles
may vary depending on the quality of thereview conducted. Review article quality
is generally measured in terms of the degree to which a systematic strategy has
been used to evaluate the evidence on aparticular topic.9-15 It is generally believedthat reviews that have been conductedsystematically are less likely to reach biased conclusions than those that havenot.9,11,15,16 For example, Antman et al9
found that, for reviews of myocardial infarction treatment, the conclusions of unsystematic reviews were often inaccurate
and out-of-date when compared with asystematic review.9 Therefore, in the literature on passive smoking, review articles may be reaching different conclusions depending on their quality.
Another factor that may influence thequality of review articles, and therefore
their conclusions, is whether they havebeen subject to peer review. Research
conducted by us and by others has foundthat, for original research articles, thequality of articles published in peer-reviewed journals is superior to the quality of articles published in non–peer-reviewed symposium proceedings.17,18 It istherefore possible that the quality of review articles also differs depending onwhether they have been peer reviewed,
and this difference in quality may lead todifferences in conclusions.
Article conclusions may also be influenced by sources of funding or author affiliations. Several studies have foundthat, for a wide range of industries, publications based on industry-funded research tend to draw pro-industry conclusions.19-24 Similarly, studies have found

Review Articles About Passive Smoking—Barnes & Bero©1998 American Medical Association. All rights reserved.

that authors of review articles tend to
draw conclusions that are consistent with
their professional affiliations.25,26 In theliterature on passive smoking, it is therefore plausible that review article conclusions would be associated with tobacco
industry sponsorship or tobacco industry–affiliated authors.
The specific topic of a review may also
play a role in what conclusion is reached.
For example, it is possible that passive
smoking is truly associated with lungcancer and heart disease in adults, but
not with brain tumors in children. One
would therefore expect review articles
on these different topics to reach different conclusions about the health effectsof passive smoking.
Finally, one might expect the year of
publication of a review article to be associated with its conclusion. For example, areview article published during the mid
1980s would be based on fewer original
research articles than one published today, and it therefore might be less likely
to reach a firm conclusion about the healtheffects of passive smoking.
The goal of our study was to evaluate
the quality of review articles on the healtheffects of passive smoking and to determine whether the conclusions of review
articles are primarily associated with
their quality or with other article characteristics. Our a priori hypotheses werethat review articles concluding that passive smoking is not harmful would tend to
be poor in quality, published in non–peerreviewed symposium proceedings, andwritten by investigators with tobacco industry affiliations. We also examined the
topic of the review and the year of publication as potential confounding factors.
METHODS
Article Identification
Review articles on the health effects ofpassive smoking were identified by searching MEDLINE and EMBASE from 1980
through 1995 using a variety of key words
and subject headings related to passive
smoking and review and meta-analysis.
The search strategy was developed in consultation with a librarian and was basedon the strategy used by the Cochrane Collaboration, an international group dedicated to conducting systematic reviews of
the biomedical literature.27 Additional review articles were identified from a database of symposium articles on passive
smoking that had been gathered for aprevious study.8 These articles wereoriginally identified by searching
MEDLINE, CATALOG, DIALOG, Conference Papers Index, TOXLINE, and International Guide to Periodicals from 1965
through 1993 for symposium proceedings
related to passive smoking; in addition,
JAMA, May 20, 1998—Vol 279, No. 19

Table 1.—Criteria Used to Evaluate Quality of Review Articles on the Health Effects of Passive Smoking
No. (%) of Articles
Partially or Completely
Satisfying Criterion*
Criteria(N = 106)

1. Was purpose of the review clearly stated?
2. Did the authors clearly describe their strategy for identifying primary researchstudies on the review topic?
3. Was the search strategy appropriate?
4. Did the authors clearly report their criteria for deciding which studies to include
and exclude?
5. Were the inclusion/exclusion criteria appropriate?
6. Did the authors clearly report their criteria for assessing the quality/validity ofstudies included?
7. Was the validity assessment appropriate?
8. Did the authors clearly report their strategy for combining study results (either
qualitatively or quantitatively)?
9. Were study results combined appropriately?
10. Were the findings clearly summarized (either graphically or in words)?
11. Did the authors adequately discuss data limitations and study inconsistencies?
12. Were the stated conclusions supported by the data presented?
Mean (SD) quality score

95 (90)18 (17)13 (12)42 (40)27 (25)49 (46)44 (42)31 (29)23 (22)59 (56)64 (60)59 (56)0.36 (0.20)*Both quality assessors agreed that the criterion had been either partially or completely satisfied.

2 symposia were identified through Tobacco Institute press releases.
An article was included if it met the following criteria: (1) its stated or implied
purpose was to review the scientific evidence suggesting that passive smoking is
associated with 1 or more health outcomes; (2) it focused specifically on thehealth effects of passive smoking, rather
than reviewing several causes of a particular disease; (3) it was written in English; and (4) it was published between
1980 and 1995. An article was excluded if
it reviewed aspects of passive smoking
other than health, such as exposure assessment or policy issues; if it discussed
several different risk factors for disease,rather than focusing on the effects of passive smoking; or if it was an editorial, commentary, or letter to the editor. A total of
106 articles that satisfied these inclusionand exclusion criteria were identified.
Quality Assessment
We hired 2 independent assessors, bothof whom had experience conducting systematic reviews, to evaluate the quality of
the review articles identified. Assessors
were trained to use our quality assessment instrument and were provided witha comprehensive set of instructions foruse during the study. Quality assessors
were blinded to our study hypotheses andwere told that the sole purpose of thestudy was to evaluate the quality of review articles on the health effects of passive smoking. In addition, assessors wereblinded to all identifying characteristicsof the articles: author names and affiliations, journal titles, acknowledgments,
and dates of publication were removed
completely. Articles were sent to assessors in a random order using a random
number generator on a computer. Assessors stated that they had never been affiliated in any way with either the tobacco
industry or tobacco control groups andthat they had not previously reviewed theliterature on passive smoking.
Review article quality was evaluatedusing a slightly modified version of the
Oxman instrument, which is the only instrument available for assessing review
article quality that has been publishedand tested for validity and reliability.28,29
The criteria used to evaluate review article quality are listed in Table 1: items 2through 9 and item 12 were based on the
Oxman instrument. Items 1, 10, and 11
were added because they have been usedby other researchers to evaluate thequality of reviews.10,11,25,30
For each criterion, the quality assessor could answer yes (2 points), partial (1point), no (0 points), or can’t tell (0points), and the quality score was thenumber of points awarded divided by 24,
the total number of points possible. The
quality score could therefore haveranged from 0 (lowest) to 1 (highest).
Analyses were based on the mean quality score (the average of the 2 assessors’scores). If the assessors’ scores differed bymore than 1 SD (0.20 point), they wereasked to discuss their answers until they
achieved consensus, and the consensus
score was used. Seventeen percent (18/106) of the articles were reevaluated using this consensus process. Agreement between reviewers was evaluated using themethod proposed by Bland and Altman.31
The median difference between reviewers’ scores was 0, and the 2.5%, 25%, 75%,
and 97.5% quantiles were −0.21, −0.04, 0.13,
and 0.21, respectively. This means that 95%of the time, reviewers’ scores were within
0.21 of each other (approximately 1 SD),on a scale from 0 to 1. The correlation between the 2 reviewers’ scores was 0.87.
Article Conclusions
Articles were classified as concludingthat passive smoking is either harmful or
not harmful. The conclusion was classi-

Review Articles About Passive Smoking—Barnes & Bero©1998 American Medical Association. All rights reserved.

1567

Table 2.—Descriptive Characteristics of Review
Articles on the Health Effects of Passive Smoking

Table 3.—Relationship Between Article Conclusions
and Author Affiliations

No. (%)*

No. (%) of Reviews

Characteristics
Conclusion
Passive smoking harmful
Passive smoking not harmful
Type of review
Systematic
Unsystematic
Peer review status
Peer reviewed
Non–peer reviewed
Missing
Author affiliation
Tobacco industry
Non–tobacco industry
Topic
Lung cancer
Heart disease
Respiratory disorders
Multiple health outcomes
MiscellaneousYears of publication
1980-1986
1987-1992
1993-1995

of Articles(N = 106)67 (63)39 (37)11 (10)95 (90)64 (60)39 (37)3 (3)31 (29)75 (71)27 (25)10 (9)
17 (16)44 (42)8 (8)16 (15)47 (44)43 (41)*Percentages may not sum to 100 because ofrounding.

fied as harmful if the authors stated that
passive smoking was definitely or probably harmful. The conclusion was classified as not harmful if the authors statedthat passive smoking was definitely or
probably not harmful, that the statisticalassociation between passive smoking andadverse health outcomes was attributable to poor study design or bias, or thatthe evidence was inconclusive. Articles
concluding that the evidence was inconclusive were classified in the not harmful
category because this conclusion is consistent with an acceptance of the null hypothesis that there is no relationship between passive smoking and disease.
Article conclusions were classified independently by the 2 quality assessors,
who were blinded to study hypotheses
and all identifying aspects of the articles,
and by one of us (D.E.B.), who was blinded
to article quality scores. Interrater agreement was excellent: all 3 raters agreed on
the conclusion category for 89% (94/106)of the articles (overall k=0.83). When all 3
raters did not agree on the article conclusion category, the category assigned by
the majority was used.
Other Article Characteristics
Other descriptive characteristics ofthe articles were classified by one of us(D.E.B.), who was blinded to article quality scores. If the classification was unclear, the principal investigator (L.A.B.)
was consulted.
Peer Review Status.—The peer review status was classified as either peer
reviewed or non–peer reviewed based onstatements in the parent publication. A
publication was considered peer reviewed if it stated that it was peer re1568

JAMA, May 20, 1998—Vol 279, No. 19

Article Conclusion
Passive smoking harmful
Passive smoking not harmful
SignificanceTobaccoAffiliatedAuthors(n = 31)Non–
TobaccoAffiliatedAuthors(n = 75)

2 (6)
65 (87)29 (94)10 (13)x21 = 60.69; P,.001

viewed, if it published a list of peer reviewers, or if it required that multiple
manuscript copies be submitted for review prior to publication; otherwise, it
was considered non–peer reviewed. Peerreview status was classified as missing
for 3 articles for which we were unable toobtain the publications’ instructions for
authors. These articles were automatically dropped from multivariate analyses
in which the peer review status variable
was included in the model.
Author Affiliation.—Of the 106 articles in our study, 77% failed to disclose
the sources of funding for the research.
Therefore, we assessed potential financial conflicts of interest by classifying theauthors of the articles as either tobacco
industry affiliated or non–tobacco industry affiliated. An article was classified ashaving tobacco industry–affiliated authors if 1 or more of the authors had ever(1) received funding from a tobacco company or the Tobacco Institute, based on
acknowledgments in articles gathered
for this study and for a prior study of theliterature on passive smoking18; (2) received funding from the tobacco industry–financed Council for Tobacco Research special projects division, basedon a published list32; (3) received funding
from the tobacco industry–financed
Center for Indoor Air Research (CIAR)
for a special-reviewed project, based on
information gathered from CIAR for aprior study19; (4) submitted a statement
on behalf of the tobacco industry regarding the EPA’s risk assessment on passive smoking, based on information gathered from the EPA for a prior study33; or(5) had participated in at least 2 tobacco
industry–sponsored symposia, based on
information gathered for a prior study.8
Otherwise, the article was classified ashaving non–tobacco-affiliated authors.
Article Topic.—The article topic wasclassified as lung cancer, heart disease,respiratory disease, multiple health outcomes, or other health effect.
Year of Publication.—The year of
publication was analyzed both continuously and categorically as 1980-1986,
1987-1991, or 1992-1995. These categorizations were used because the surgeon
general and the National Academy of
Sciences both published consensus re-ports on the health effects of passive
smoking in 1986, and the EPA publishedits risk assessment of passive smoking
early in 1992, and we hypothesized thatthe conclusions of review articles in thescientific literature might be influenced
by publication of these landmark documents.
Statistical Analyses
To compare mean quality scores invarious groups we used t tests and analysis of variance. Associations between categorical variables were evaluated using
x2 analyses. Multiple logistic regression
was used to determine which article characteristics were most highly associatedwith concluding that passive smoking is
not harmful to health. The predictor variables were article quality score (analyzed
as a continuous variable), peer review status, author affiliation, article topic, andyear of publication (examined as both acontinuous variable and a categoricalvariable). Multilevel categorical variables were modeled using indicator variables. Sensitivity analyses and diagnostic tests were performed to evaluate themultiple logistic regression model. Twotailed P values less than .05 were considered statistically significant in all tests.
RESULTS
Descriptive characteristics of the review articles identified are presented inTable 2. Overall, 37% of articles concluded that passive smoking is not harmful. Most reviews were unsystematic but
had been peer reviewed.
Thirty-one review articles (29%) were
written by authors with tobacco industry
affiliations. For 30 of the 31 articles, theauthor was affiliated with the tobacco industry either prior to or concurrent withthe year of publication of the review. For
the 1 review that was the exception, thearticle was published during the year
prior to the first documented affiliation.
Table 1 presents our results related tothe quality of review articles. The meanquality score was 0.36 (SD, 0.20; range,
0.04-0.94). This means that the average
review article in our study satisfied only
one third of the criteria on our quality
assessment instrument.
Table 3 shows that there was a strong
relationship between the conclusion of areview and the affiliation of its authors.
Ninety-four percent (29/31) of reviews by
tobacco industry–affiliated authors concluded that passive smoking is not harmful, compared with 13% (10/75) of reviewsby authors without tobacco industry affiliations (P,.001). In our study, the relative risk (RR) of concluding that passive
smoking is not harmful, comparing tobacco industry–affiliated authors withnonaffiliated authors, was 7.0 (95% con-

Review Articles About Passive Smoking—Barnes & Bero©1998 American Medical Association. All rights reserved.

fidence interval [CI], 3.9-12.6). The corresponding odds ratio (OR) was 94.2 (95%CI, 19.4-457.6). These measures are dissimilar because the outcome (concludingthat passive smoking is not harmful) was
not rare among the group of tobacco industry–affiliated authors.
The results of the full logistic regression model are presented in Table 4. The
odds that a review article with tobacco
industry–affiliated authors would conclude that passive smoking is not harmful were 88.4 times higher than the odds
for a review article with non–tobaccoaffiliated authors, when controlling forarticle quality, peer review status, article topic, and year of publication (95%CI, 16.4-476.5; P,.001).
We conducted sensitivity analyses to determine whether this finding was limited
to a particular subset of articles in our
sample. When we limited the analysis tohigher-quality articles (defined as articles receiving mean quality scores of 0.50
or higher), tobacco industry affiliation remained the only factor associated with concluding that passive smoking is not harmful (OR, 85; 95% CI, 3-2134; P=.007). (The
article topic variable was dropped from thisanalysis because of small cell sizes that produced instability in the model.) Similarly,
tobacco industry affiliation was the only
factor associated with concluding that passive smoking is not harmful when theanalysis was restricted to peer-reviewed
articles only (OR, 93; 95% CI, 9-945;
P,.001). No matter how we analyzed thedata, tobacco industry affiliation was the
only factor associated with concluding that
passive smoking is not harmful to healthin the multivariate analyses.
We also stratified the analysis by author affiliation to determine whether,
within either the group of articles by tobacco industry–affiliated authors or thegroup of articles by non–tobacco-affiliated authors, review article conclusions
might be associated with other factors.
However, within each group, we foundno other factors that were significantly
predictive of review article conclusions.
To determine whether our results had
been influenced by classification of reviews with “inconclusive” findings in the“passive smoking not harmful” category,
we reanalyzed the data after excludinginconclusive reviews. This resulted in exclusion of 24 reviews (17 by tobacco-affiliated authors, 7 by nonaffiliated authors).
Themagnitudeoftheassociationbetween
author affiliation and review article conclusion was stronger in this analysis (OR,130; 95% CI, 20-862; P,.001).
Finally, we conducted diagnostic tests
to determine whether some articles
were highly influential in our analyses.
We found that 2 articles by tobacco industry–affiliated authors that concluded
JAMA, May 20, 1998—Vol 279, No. 19

Table 4.—Factors Associated With Concluding That Passive Smoking Is Not Harmful to Health: Multiple Logistic
Regression Analysis
Odds Ratio*
Factors
Mean quality score (continuous)
Peer review status
Non–peer reviewed vs peer reviewed(95% Confidence Interval)

P
Value

1.5 (,0.1-67.5).83

1.3 (0.3-5.4).70Author affiliation
Tobacco industry vs non–tobacco industry

88.4 (16.4-476.5)

,.001

Topic
Lung cancer vs multiple health effects

1.6 (0.2-10.3).63

Heart disease vs multiple health effects

1.6 (0.2-14.7).67

Respiratory disorders vs multiple health effects

1.8 (0.3-11.9).56

Other health effects vs multiple health effects

4.6 (0.6-32.8).13

1.1 (0.9-1.3).45

Year of publication (continuous)*Odds ratio corresponds to factors associated with concluding that passive smoking is not harmful.

passive smoking is harmful were highly
influential; however, when these 2 articles were excluded from the analysis,
100% of the reviews by tobacco industry–affiliated authors concluded that
passive smoking is not harmful.
COMMENTThe goal of our study was to determine whether review article quality, author affiliation, or other article characteristics were associated with concluding that passive smoking is not harmful
to health. We had initially hypothesizedthat review articles would be more likely
to conclude that passive smoking is notharmful if they were poor in quality, published in non–peer-reviewed journals or
symposium proceedings, or written byauthors with tobacco industry affiliations. We also speculated that the topic
of a review and its year of publication
might be associated with its conclusion.
We found that very few reviews had
been conducted systematically, resulting in overall mean quality scores thatwere quite low. The low quality scores
may be attributable in part to poor reporting in some of the articles; for example, several authors implied that they
had conducted a review of the literatureby making statements such as “there are
currently x number of published studies
on a particular topic.” These results
highlight the need for accurate reporting of study methods in reviews as wellas original research articles.
The quality of a review was not associated with its conclusion when controlling
for the effect of author affiliation. Using
multivariate logistic regression analysis,
the only factor that predicted a review article’s conclusion was whether its author
was affiliated with the tobacco industry.
This finding was consistent and emerged
no matter how we analyzed the data.
A total of 10 reviews34-43 by authors classified as non–industry affiliated concluded that passive smoking may not be
harmful. In 7 cases,34-40 the authors foundthat the evidence was inconclusive. For ex-

ample, 1 review37 stated that “[w]hile a few
well-designed studies demonstrate a significant effect of passive smoking on childhealth, most studies had significant design problems that prevent reliance on
their conclusions.” Two of the other 3 reviews42,43 had authors who had some affiliation with the tobacco industry, although
they did not meet the stringent criteria
used to define affiliation in this study; inboth cases, the authors had participatedin a single tobacco industry–sponsored
symposium prior to or concurrent withpublication of the review. Therefore, we
identified only 1 review40 written by an author without any known tobacco industry
affiliations that concluded that passive
smoking is not harmful to health.
Our findings suggest that the discrepancy between consensus documents andpublished reviews related to the healthhazards of passive smoking is primarily
attributable to large numbers of reviews
written by authors with tobacco industry
affiliations. For example, although 37%(39/106) of reviews in our study concluded
that passive smoking is not harmful, 74%(29/39) of these were written by authors
with tobacco industry affiliations. From
the time our search ended in 1995, at least
17 reviews of the health effects of passive
smoking have been published. Two of themost recent reviews by authors not affiliated with the tobacco industry conclude
that passive smoking is harmful.44,45
These findings suggest that the tobacco
industry may be attempting to influencescientific opinion by flooding the scientific
literature with large numbers of review
articles supporting its position that passive smoking is not harmful to health. Thisconclusion is consistent with the industry’s previous strategies related to tobacco. For example, internal documents
have shown that one of the tobacco industry’s key strategies has been to suggestthat there is doubt or controversy about
scientific knowledge related to the healtheffects of tobacco.46-48 In this way, the industry is able to argue that government
regulations are not warranted.

Review Articles About Passive Smoking—Barnes & Bero©1998 American Medical Association. All rights reserved.

1569

Our findings are unlikely to be attributable to bias. Review articles wereidentified using a systematic strategy
and well-defined inclusion and exclusion
criteria. Article quality was evaluatedby independent assessors who weretrained, used a slightly modified version
of a valid and reliable instrument, andwere blinded to study hypotheses. In
addition, article conclusions were classified independently by 3 people, 2 ofwhom were blinded to all identifying aspects of the articles, including authornames and affiliations. Furthermore, we
do not feel that our findings were biased
by inclusion of symposium studies that
we had identified for a prior study, because our results were the same whenthese articles were excluded.
Our findings are consistent with previous research on both the quality and conclusions of review articles. Several studies have found that most publishedreviews are unsystematic and that their

quality is therefore low.10,11,13,25 In addition, other studies have found an association between the conclusions of review articles and the affiliations of their authors.
For example, Assendelft et al25 found that
reviews were more likely to conclude thatspinal manipulation was beneficial if oneof the authors was a spinal manipulator.
Similarly, Chalmers et al26 showed that,for several types of controversial procedures, an author’s enthusiasm for theprocedure was associated with his or her
specialty. Furthermore, several investigators have found that original research
articles that acknowledge sponsorshipfrom the pharmaceutical industry,20,21,23
the chemical industry,24 or the tobacco industry19 tend to draw pro-industry conclusions. Ultimately, the conclusion of any
review article must be based on the judgment and interpretation of the author.
Because research studies on a variety
of topics have consistently found an association between the affiliations of anThis research was sponsored by the Robert WoodJohnson Foundation (grant 024783) as part of alarger study on the content, quality, and use of
tobacco industry–sponsored research.
We would like to thank Phillip Lollar for administrative assistance; the Writing Seminar at the Institute for Health Policy Studies, University of California,SanFrancisco,andIraTager,MD,MPH,forfeedback on the manuscript; and our quality assessors,
Peggy Lopipero, MPH, and Carolyn Klassen, MPH.

lished in journal supplements compared with thequality of those published in the parent journal.
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for Indoor Air Research. J Health Polit Policy Law.
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20. Cho MK, Bero LA. The quality of drug studies
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21. Rochon PA, Gurwitz JH, Simms RW, et al. A
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22. Gotzsche PC. Methodology and overt and hidden bias in reports of 196 double-blind trials of nonsteroidal antiinflammatory drugs in rheumatoid arthritis. Controlled Clin Trials. 1989;10:31-56.
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characteristics on the outcome of retrospective cohort studies. Br J Ind Med. 1988;45:624-629.
25. Assendelft WJJ, Koes BW, Knipschild PG,
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27. Mulrow CD, Oxman A. How to Conduct a
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33. Bero LA, Glantz SA. Tobacco industry response
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author and the conclusions of his or her
published research, we feel that our findings may be generalizable to review articles on topics other than passive smoking. That is, the conclusions of a review
article may be suspect whenever the author has a financial interest in the outcome of the review. Therefore, our findings suggest that the authors of review
articles should disclose their affiliations,sources of funding, and other potential
financial conflicts of interest, and thatthe readers of review articles should consider these disclosures when deciding
how to judge an article’s conclusions.

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Review Articles About Passive Smoking—Barnes & Bero©1998 American Medical Association. All rights reserved.