# Risk Factors and Prevalence ofHelicobacter pylori Infection in Persistent High Incidence Area of Gastric Carcinoma in Yangzhong City

Authors: Yangchun Zhu; Xiaoying Zhou; Junbei Wu; Jing Su; Guoxin Zhang
Journal: Gastroenterology Research and Practice
 (2014)

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## Abstract

Aim. The aim of this study was to investigate the prevalence and risk factors of H. pylori infection in areas with high prevalence of gastric cancer in Jiangsu Province, China. Methods. A prospective epidemiologic survey of H. pylori infection was accomplished in a natural population of 5417 individuals in Yangzhong city. Questionnaires and 13C-urea breath test for H. pylori infection were performed. Results. Among 5417 subjects who completed questionnaires and 13C-urea breath test, 3435 (63.41%) were H. pylori positive. The prevalence reached a peak at the age of 30–39 years (90.82%). There was significant difference between sexes and women had a higher infection rate than men. The prevalence of H. pylori infection was also associated with eating kipper food and fried food. No association between H. pylori prevalence and smoking or drinking was found. Compared to healthy individuals, people with dyspeptic diseases (peptic ulcer, gastroenteritis) presented a high prevalence of H. pylori infection. Using multivariate logistic regression analysis, age and history of peptic ulcer and gastroenteritis were the independent predictors for H. pylori infection. Conclusions. Yangzhong city had a high prevalence of H. pylori infection and was related to several risk factors. The underlying mechanisms are needed to be further investigated.


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## Body

## 1. Introduction

Helicobacter pylori is a microaerophilic Gram-negative spiral bacterium [1]. Its helix shape is thought to have evolved to penetrate the mucoid lining of the stomach [2]. It is linked to the development of chronic gastritis, gastric ulcers, duodenal ulcers, and stomach mucosal atrophy. Moreover, Helicobacter pylori is well recognized as a class I carcinogen because chronic inflammation and atrophy can further lead to malignant transformation [3, 4]. At least half the world’s population is infected by this bacterium, making it the most widespread infection in the world, especially in the developing world where rates are estimated to be around 80% [5].H. pylori is contagious, although the exact route of transmission is not known [6, 7]. Person-to-person transmission by either the oral-oral or fecal-oral route is most likely. H. pylori may also be transmitted orally by means of fecal matter through the ingestion of waste-tainted water [2]. Many of the reported factors for H. pylori infection included poor hygiene, deficient sanitation, and crowded living conditions [8]. However, the roles of many other factors associated have not been elucidated.The aim of the current study was to determine the prevalence ofHelicobacter pylori in the census population in Yangzhong city of Jiangsu Province, where there is a high prevalence of gastric cancer, and to assess the risk factors for Helicobacter pylori by an extended anamnesis, involving data on sex, age, educational level, smoking, drinking, as well as dietary factors.


## 2. Methods

### 2.1. Study Population

A total of 5417 healthy individuals aged between 30 and 69 years old from six rural villages in Yangzhong counties, northern Jiangsu province, from August 2009 to October 2011 underwent a comprehensive medical survey at the Center for Preventive Medicine in Yangzhong hospital as part of a survey study. There are seven administrative sub-autonomous regions in Yangzhong city, 77 counties in total. We assigned a consecutive number from 1 toN numbering counties of each region. Then we used a computer programme randomly chose one county from each region, except which population is significantly less than others.All participants underwent a free screening program, including physical check-up, 13C breath test, upper gastrointestinal endoscopy, blood tests, and a doctor’s interview. The study protocol was approved by the Ethical Committee of the people’s Hospital of Yangzhong city. All participants received detailed written information about the study in advance and signed written informed consent before enrollment in the study.


### 2.2. Exclusion Criteria

The following individuals were excluded from our study: people taking medication for gastroesophageal reflux symptoms or malignant diseases; people with a history ofHelicobacter pylori (H. pylori) eradication or upper gastrointestinal surgery. Individuals with gastric or esophageal cancer detected at the time of endoscopic screening were also excluded.


### 2.3. Questionnaires

This was a population-based study. All participants had been trained before they fulfilled the questionnaires. Collected information included sex, age, height, weight, individual education level, size of family, annual family income, marital status, self-reported socioeconomic group, and smoking and drinking habits. Health status, medical history, and medications taken in the past 2 months (particularly the use of proton pump inhibitors and antibiotics) were also recorded. Each questionnaire contained a total of 57 questions possibly related toH. pyloriinfection and transmission.


### 2.4. Detection ofH. pyloriInfection

Subjects were diagnosed withH. pyloriinfection if 13C-urea breath test (13C-UBT) was positive. The 13C-UBT was performed in the morning after at least 6 hours of fasting. The system is comprised of the following components: (a) a kit containing 50 mg of 13C-urea (a 99% 13C-enriched urea tablet); (b) a packet of granulated Citrica (a 4.5 gram packet containing 4 g of citric acid, 0.149 mg of aspartame, orange aroma, FD&C yellow #6); (c) an IDcircuit-sampling device; and (d) a BreathID device. All patients received 50 mg of 13C-urea with a 4.5 gram citric acid based powder (Citrica). The IDcircuit, a continuous nasal breath sampling device, transported the breath sample from the patient to the BreathID and did not require active cooperation. All performances followed the instructions. Our cut-off value is 4%, and we considered the patients negative when the value was less than 4% and positive when the value was larger than 4%.


### 2.5. Statistical Analysis

The data were recorded and analyzed by using EPIDATA 3.1 by double-input. Stata 12.0 was used for all statistical analyses. Multivariate analyses were restricted to those subjects with all relevant data available. Aχ
2 test and Fisher’s exact test of independence were used to compare the following variables of interest: sex, age, educational level, height, weight, pulse, blood pressure, size of family, annual family income, smoking, drinking, and the history of gastroenterology diseases. All the reported P values, are two-sided, and P value < 0.05 was regarded as statistically significant for all included studies. Logistic regression was used to select significant predictor variables and to estimate odds ratios (ORs) of these variables and, if possible, to predict outcomes.


## 2.1. Study Population

A total of 5417 healthy individuals aged between 30 and 69 years old from six rural villages in Yangzhong counties, northern Jiangsu province, from August 2009 to October 2011 underwent a comprehensive medical survey at the Center for Preventive Medicine in Yangzhong hospital as part of a survey study. There are seven administrative sub-autonomous regions in Yangzhong city, 77 counties in total. We assigned a consecutive number from 1 toN numbering counties of each region. Then we used a computer programme randomly chose one county from each region, except which population is significantly less than others.All participants underwent a free screening program, including physical check-up, 13C breath test, upper gastrointestinal endoscopy, blood tests, and a doctor’s interview. The study protocol was approved by the Ethical Committee of the people’s Hospital of Yangzhong city. All participants received detailed written information about the study in advance and signed written informed consent before enrollment in the study.


## 2.2. Exclusion Criteria

The following individuals were excluded from our study: people taking medication for gastroesophageal reflux symptoms or malignant diseases; people with a history ofHelicobacter pylori (H. pylori) eradication or upper gastrointestinal surgery. Individuals with gastric or esophageal cancer detected at the time of endoscopic screening were also excluded.


## 2.3. Questionnaires

This was a population-based study. All participants had been trained before they fulfilled the questionnaires. Collected information included sex, age, height, weight, individual education level, size of family, annual family income, marital status, self-reported socioeconomic group, and smoking and drinking habits. Health status, medical history, and medications taken in the past 2 months (particularly the use of proton pump inhibitors and antibiotics) were also recorded. Each questionnaire contained a total of 57 questions possibly related toH. pyloriinfection and transmission.


## 2.4. Detection ofH. pyloriInfection

Subjects were diagnosed withH. pyloriinfection if 13C-urea breath test (13C-UBT) was positive. The 13C-UBT was performed in the morning after at least 6 hours of fasting. The system is comprised of the following components: (a) a kit containing 50 mg of 13C-urea (a 99% 13C-enriched urea tablet); (b) a packet of granulated Citrica (a 4.5 gram packet containing 4 g of citric acid, 0.149 mg of aspartame, orange aroma, FD&C yellow #6); (c) an IDcircuit-sampling device; and (d) a BreathID device. All patients received 50 mg of 13C-urea with a 4.5 gram citric acid based powder (Citrica). The IDcircuit, a continuous nasal breath sampling device, transported the breath sample from the patient to the BreathID and did not require active cooperation. All performances followed the instructions. Our cut-off value is 4%, and we considered the patients negative when the value was less than 4% and positive when the value was larger than 4%.


## 2.5. Statistical Analysis

The data were recorded and analyzed by using EPIDATA 3.1 by double-input. Stata 12.0 was used for all statistical analyses. Multivariate analyses were restricted to those subjects with all relevant data available. Aχ
2 test and Fisher’s exact test of independence were used to compare the following variables of interest: sex, age, educational level, height, weight, pulse, blood pressure, size of family, annual family income, smoking, drinking, and the history of gastroenterology diseases. All the reported P values, are two-sided, and P value < 0.05 was regarded as statistically significant for all included studies. Logistic regression was used to select significant predictor variables and to estimate odds ratios (ORs) of these variables and, if possible, to predict outcomes.


## 3. Results

### 3.1. Prevalence ofH. pylori Infection and Social Factors

Among 5500 subjects, 5417 completed both the questionnaire and theH. pylori detection test and were qualified for inclusion in data analysis. The mean age was 50.15 years old. There were 2342 men, whose average age was 50.27 years, and the rest were women, whose average age was 50.06 years. The overall prevalence of H. pylori was 63.41%. The prevalence of H. pylori among male and female was 61.74% and 64.47%, respectively, suggesting that there was a significant difference between sexes (P
=
0.026) and women had a higher infection rate than men. As shown in Table 1, 30–39 years had the highest rate of H. pylori infection than other age groups.Table 1
Relationships between prevalence ofH. pylori infection and general information.
Factors
No. of subjects in Hp positive group
No. of subjects in Hp negative group
Total no. of subjects
Prevalence
OR (95% CI)
P value
Sex
Male
1446
896
2342
61.74%
1.00
1.000
Female
1989
1086
3075
64.68%
0.97 (0.87–1.08)
0.573
Age
30–39
267
27
294
90.82%
1.00
1.000
40–49
1508
818
2326
64.83%
0.19 (0.13–0.28)
0.000
50–59
1374
921
2295
59.87%
0.16 (0.11–0.24)
0.000
60–69
285
215
500
57.00%
0.14 (0.09–0.22)
0.000
BMI
Underweight
67
34
101
66.34%
1.00
1.000
Normal
2178
1319
3497
62.28%
0.87 (0.58–1.32)
0.516
Obese
1190
629
1819
65.42%
1.02 (0.67–1.55)
0.943
Marriage
Unmarried
16
5
21
76.19%
1.97 (0.73–5.35)
0.183
Married
3326
1930
5256
63.28%
1.00
1.000
Divorced
27
18
45
60.00%
0.79 (0.44–1.44)
0.446
Loss of spouse
66
29
95
69.47%
1.32 (0.85–1.05)
0.217
Education level
Illiterate
89
38
127
70.08%
1.38 (0.94–2.04)
0.100
Primary school
1824
1085
2909
62.70%
1.00
1.000
Middle school
1333
746
2079
64.12%
1.05 (0.94–1.18)
0.371
University or above
189
113
302
62.58%
0.94 (0.74–1.20)
0.617
Number of family members
1
36
16
52
69.23%
1.00
1.000
2
237
151
388
61.08%
0.70 (0.37–1.30)
0.257
3
1000
602
1602
62.42%
0.74 (0.41–1.34)
0.320
4
491
280
771
63.68%
0.78 (0.42–1.43)
0.421
5
1466
820
2286
64.13%
0.79 (0.44–1.44)
0.449
6
152
83
235
64.68%
0.81 (0.43–1.55)
0.533
7 and above
53
30
83
63.86%
0.69 (0.25–1.92)
0.48
Annual income
≤5000
104
41
145
71.72%
1.00
1.000
5001–20000
549
367
916
59.93%
0.81 (0.55–1.16)
0.249
20001–50000
2235
1248
3483
64.17%
0.86 (0.61–1.23)
0.418
50001–80000
450
258
708
63.56%
0.89 (0.61–1.30)
0.546
>80000
97
68
165
58.79%
0.78 (0.49–1.24)
0.299The prevalence ofH. pylori in the group with one member only (69.23%) was higher than that in the group with other members, without statistical difference. As for the association of prevalence and annual family income, in the six groups (with an average level of RMB 35890.95, approximately $US 5000), we found that individuals with an annual family income of RMB >80000 had the lowest risk of H. pylori infection (58.79%), whereas those with annual family income of RMB5000 or less had the highest risk of H. pylori infection (71.72%), and there was a significant difference between the groups (P
=
0.017). Moreover, our study showed that the higher annual family income was, the lower the prevalence of H. pylori, which is significant in test for trend (P
=
0.022). As for the education level, H. pylori infection is higher in illiterate (70.08%) and those who received university education had the lowest H. pylori infection rate (62.58%). But there were no significant associations seen for the subjects’ level of education in general (P
=
0.138).Regarding the body mass index (BMI) value, healthy people (BMI = 18.5 to 24.9) had lowestH. pylori infection rate (62.28%) while those underweight (BMI < 18.5) people had highest infection rate (66.34%), but there was no significant difference between the groups.There was no apparent association between theH. pylori infection and other social factors, such as marriage status (P
=
0.369).


### 3.2. Relationships betweenH. pyloriInfection and Dietary Factors, Smoking, and Drinking

The results suggest thatH. pylori infection increased for subjects who ate vegetable more than once a day (65.71%), compared to those who ate it less than every other day (64.71%, ) and every other day to once a day (63.19% P
=
0.309), and there was no difference in χ
2 for trend (P
=
0.562), as shown in Table 2.Table 2
Relationships between prevalence ofH. pylori infection and dietary-related factors.
Factors
No. of subjects in Hp positive group
No. of subjects in Hp negative group
Total no. of subjects
Prevalence of Hp
OR (95% CI)
P value
Frequency of eating vegetables
<Every other day
22
12
34
64.71%
1.00
1.000
Every other day-once a day
3114
1814
4928
63.19%
0.94 (0.46–1.89)
0.853
>Once a day
299
156
455
65.71%
1.05 (0.51–2.19)
0.844
Frequency of eating fruits
0
23
10
33
69.70%
1.00
1.000
<Every other day
3199
1851
5050
63.35%
0.64 (0.30–1.39)
0.261
Every other day-once a day
213
121
334
63.77%
0.72 (0.33–1.61)
0.427
Frequency of eating milk, egg, and meat
0
2
0
2
100.00%
1.00
1.000
<Every other day
3211
1863
5074
63.28%
1.38 (1.01–1.88)
0.039
Every other day-once a day
113
58
171
66.08%
1.35 (0.88–2.09)
0.172
>Once a day
109
61
170
64.12%
1.00
Frequency of eating beans
0
8
3
11
72.73%
1.00
1.000
<Every other day
3229
1874
5103
63.28%
1.00 (0.29–3.43)
0.997
Every other day-once a day
198
105
303
65.35%
0.81 (0.23–2.84)
0.746
Frequency of eating onion and garlic
0
11
6
17
64.71%
1.00
1.000
<Every other day
3271
1880
5151
63.50%
1.21 (0.46–3.19)
0.695
Every other day-once a day
146
92
238
61.34%
1.24 (0.45–3.37)
0.677
>Once a day
7
4
11
63.64%
0.84 (0.18–3.88)
0.823
Frequency of eating pickled foods
0
2175
1311
3486
62.39%
1.00
1.000
<Every other day
448
223
671
66.77%
0.87 (0.73–1.03)
0.103
Every other day-once a day
810
447
1257
64.44%
0.97 (0.85–1.11)
0.683
>Once a day
2
1
3
66.67%
1.12 (0.10–12.44)
0.923
Frequency of eating fried foods
0
3138
1826
4964
63.22%
1.00
1.000
<Every other day
294
155
449
65.48%
1.14 (0.93–1.40)
0.211
Every other day-once a day
3
1
4
75.00%
0.58 (0.08–4.14)
0.59
Frequency of eating hot foods
0
3242
1856
5098
63.59%
1.00
1.000
<Every other day
191
125
316
60.44%
0.90 (0.71–1.14)
0.375
Every other day-once a day
2
1
3
66.67%
1.15 (0.10–12.66)
0.911In contrast, the prevalence ofH. pylori was highest in subjects who never ate fruits (67.70%), compared to the lowest infection rate in those who ate fruits less than every other day (63.35%, P
=
0.45), and there was no significant difference in χ
2 for trend (P
=
0.786).Our study also showed that those who never ate milk, egg, or meat had 100% infection ofH. pylori and people who ate less than every other day had the lowest infection rate (63.28%, P
=
0.535). People who ate pickled food less than every other day had the highest infection (66.77%), while those who never ate pickled food had the lowest infection rate (62.39%, P
=
0.032).However, there was no apparent association betweenH. pylori infection and other dietary-related factors, such as beans consumption (P
=
0.625), onion and garlic use (P
=
0.926), eating fried foods (P
=
0.065), and hot food (P
=
0.526).Table3 shows that there was no association between the prevalence of H. pylori infection and the use of tobacco or alcohol (Table 3). But there was significant relationship observed between H. pylori infection and the amount of cigarettes which a person had been smoking per day. Our data showed that people smoking 1 to 10 cigarettes per day had significantly higher rate of H. pylori infection than people smoking 11 to 20 cigarettes (P
=
0.041).Table 3
Relationships between prevalence ofH. pylori infection and smoking and alcohol drinking.
Factors
No. of subjects in Hp positive group
No. of subjects in Hp negative group
Total
Prevalence
OR  (95% CI)
P value
Smoking
No. of cigarettes smoked per day
0
2691
1535
4226
63.68%
1.00
1.000
1–10
191
108
299
63.88%
0.86   (0.68–1.09)
0.218
11–20
509
298
807
63.07%
1.19   (1.01–1.40)
0.036
>20
44
41
85
51.76%
0.80   (0.52–1.23)
0.321
The period of smoking  (year)
0
2691
1535
4226
63.68%
1.00
1.000
0–10
186
105
291
63.92%
1.18   (0.92–1.52)
0.183
11–20
389
221
610
63.77%
1.14   (0.95–1.36)
0.152
>20
169
121
290
58.28%
0.88   (0.69–1.12)
0.286
Drinking
589
313
902
65.30%
Beer
15
14
29
51.72%
Beer consumption per day (mL/d)
0
3420
1968
5388
63.47%
1.00
1.000
0–200
4
4
8
50.00%
0.96   (0.23–4.04)
0.960
201–500
9
10
19
47.37%
2.17   (0.72–6.54)
0.170
>500
2
0
2
100.00%
0.58   (0.04–9.25)
0.699
The period of drinking beer (year)
0
3420
1968
5388
63.47%
1.00
1.000
0–10
10
9
19
52.63%
2.17   (0.72–6.54)
0.169
11–20
5
2
7
71.43%
0.77   (1.72–3.45)
0.734
>20
0
3
3
0.00%
1.74   (0.18–16.69)
0.633
Wine
577
301
878
65.72%
Wine consumption per day (g/d)
0
2858
1681
4539
62.97%
1.00
1.000
<250
480
248
728
65.93%
1.07   (0.90–1.25)
0.445
251–500
95
53
148
64.19%
0.96   (0.68–1.34)
0.791
>500
2
0
2
100.00%
The period of drinking wine  (year)
0
2858
1681
4539
62.97%
1.00
1.000
0–10
186
110
296
62.84%
1.16   (0.90–1.48)
0.250
11–20
275
136
411
66.91%
1.04 (0.85–1.29)
0.686
>20
116
55
171
67.84%
0.90 (0.66–1.23)
0.521


### 3.3. Relationships betweenH. pyloriInfection and Upper Gastroduodenal Diseases

The prevalence ofH. pylori infection in individuals with history of gastroenteral diseases (64.60%) was higher than those without a history of this disease (57.26%, P
=
0.000) (Table 4).Table 4
Relationships between prevalence ofH. pylori infection and history of digestive diseases.
Factors
No. of subjects in Hp positive group
No. of subjects in Hp negative group
Total no. of subjects
Prevalence of Hp
OR (95% CI)
P value
History of digestive diseases
501
374
875
57.26%
0.71 (0.61–0.82)
0.000
Gastroenteritis
324
262
586
55.29%
0.67 (0.57–0.80)
0.000
Peptic ulcer
91
87
178
51.12%
0.57 (0.42–0.76)
0.000
Esophagitis
53
32
85
62.35%
0.95 (0.61–1.49)
0.838
Hepatitis
73
46
119
61.34%
0.91 (0.63–1.33)
0.636


### 3.4. Logistic Regression Model Analysis forH. pylori Infection

Thirty-six variables possibly related toH. pylori infection were assessed by using univariate logistic regression models analysis. The prevalence of H. pylori infection had a positive correlation with gender (P
=
0.022), kipple food (P
=
0.012), frequency of eating pickled food (P
=
0.052), frequency of eating fried foods (P
=
0.036), and digestive diseases (P
=
0.000), and negative correlation with factors of age (P
=
0.000), gastroenteral inflammation (P
=
0.000) and peptic ulcer (P
=
0.000) (Table 5(a)).Table 5
(a)  Risk factors forH. pylori infection. (b)  Logistic multivariate regression analysis of H. pylori infection.
(a)
Risk factors
B
Sx
Wald
P value
OR
95% CI
Gender
0.13
0.057
5.207
0.022
1.14
1.01–1.27
Age
-
0.037
0.004
78.336
0.000
0.96
0.95–0.97
Marriage
0.073
0.1
0.527
0.468
1.08
0.88–1.31
Education level
-
0.011
0.044
0.064
0.800
1.00
0.91–1.08
Family number
0.013
0.02
0.436
0.570
1.01
0.97–1.05
Annual income
0.000
0.000
0.212
0.748
1.00
1.00–1.00
Smoking
-
0.076
0.08
0.902
0.722
0.98
0.85–1.11
Number of cigarettes per day
0.003
0.003
0.934
0.347
1.00
0.99–1.01
The period of smoking
-
0.059
0.036
2.643
0.356
0.97
0.91–1.03
Alcohol
0.108
0.09
1.458
0.404
1.66
0.92–1.24
Beer  consumption per day
0.000
0.001
0.039
0.455
1.00
1.00–1.00
The period of drinking beer
-
0.033
0.037
0.768
0.220
0.97
0.93–1.02
Wine consumption per day
0.001
0.001
0.862
0.208
1.00
1.00–1.00
The period of drinking beer
0.003
0.007
0.177
0.333
1.00
0.99–1.01
Tea
-
0.043
0.137
0.099
0.831
0.97
0.74–1.27
Frequency of eating vegetables
0.002
0.003
0.488
0.485
1.00
0.99–1.01
Fruit
-
0.166
0.184
0.812
0.336
0.84
0.58–1.20
Frequency of eating fruits
-
0.001
0.005
0.011
0.918
1.00
0.99–1.01
Meat, milk, and eggs
-
2.527
3.536
0.511
Frequency of eating milk, egg, and meat
0.002
0.003
0.31
0.577
1.00
0.99–1.01
Bean
-
0.395
0.715
0.305
0.524
0.65
0.17–2.45
Frequency of eating beans
0.002
0.006
0.151
0.698
1.00
0.99–1.01
Onion and garlic
-
0.059
0.42
0.02
0.738
0.88
0.41–1.89
Frequency of eating onion and garlic
0.011
1.007
2.516
0.112
1.01
1.00–1.02
Kipper food
0.164
0.065
6.349
0.012
1.16
1.03–1.30
Frequency of eating pickled foods
0.006
0.003
3.774
0.052
1.01
1.00–1.02
Fried food
0.183
0.132
1.931
0.245
1.13
0.92–1.38
Frequency of eating fried foods
0.073
0.035
4.309
0.036
1.08
1.00–1.15
Scalding food
-
0.347
0.147
5.568
0.321
0.89
0.70–1.12
Frequency of eating hot foods
0.009
0.033
0.072
0.788
1.01
0.95–1.08
Digestive diseases
0.171
0.207
0.683
0.000
0.71
0.61–0.82
Gastroenteral inflammation
-
0.523
0.206
6.457
0.000
0.67
0.57–0.80
Peptic ulcer
-
0.64
0.217
8.706
0.000
0.57
0.42–0.76
Esophageal inflammation
-
0.047
0.226
0.044
0.838
0.95
0.61–1.49
Hepatitis
-
0.239
0.26
0.85
0.636
0.91
0.63–1.33
BMI
-
0.001
0.001
0.685
0.426
1.00
1.00–1.00
(b)
Risk factors
B
S.E.
Wald
P value
OR
95% CI
Gender
0,112
0.058
3.756
0.053
1.12
1.00–1.25
Age
-
0.04
0.004
88.709
0.000
0.96
0.95–0.97
Kipper food
0.142
0.115
1.524
0.217
1.15
0.92–1.44
Frequency of eating pickled foods
-
0.003
0.006
0.254
0.614
1.00
0.99–1.01
Frequency of eating fried foods
0.045
0.035
1.697
0.193
1.05
0.98–1.12
Digestive disease
0.131
0.155
0.705
0.401
1.14
0.84–1.54
Gastroenteritis
-
0.493
0.166
8.795
0.003
0.61
0.44–0.85
Peptic ulcer
-
0.51
0.193
7.001
0.008
0.6
0.41–0.88These eight factors then were introduced in the multivariate logistic regression analysis. Factors ultimately into the main effects model were independent factors forH. pylori infection. They were age (P
=
0.000), history of gastroenteritis (P
=
0.003), and history of peptic ulcer (P
=
0.008) (Table 5(b)).


## 3.1. Prevalence ofH. pylori Infection and Social Factors

Among 5500 subjects, 5417 completed both the questionnaire and theH. pylori detection test and were qualified for inclusion in data analysis. The mean age was 50.15 years old. There were 2342 men, whose average age was 50.27 years, and the rest were women, whose average age was 50.06 years. The overall prevalence of H. pylori was 63.41%. The prevalence of H. pylori among male and female was 61.74% and 64.47%, respectively, suggesting that there was a significant difference between sexes (P
=
0.026) and women had a higher infection rate than men. As shown in Table 1, 30–39 years had the highest rate of H. pylori infection than other age groups.Table 1
Relationships between prevalence ofH. pylori infection and general information.
Factors
No. of subjects in Hp positive group
No. of subjects in Hp negative group
Total no. of subjects
Prevalence
OR (95% CI)
P value
Sex
Male
1446
896
2342
61.74%
1.00
1.000
Female
1989
1086
3075
64.68%
0.97 (0.87–1.08)
0.573
Age
30–39
267
27
294
90.82%
1.00
1.000
40–49
1508
818
2326
64.83%
0.19 (0.13–0.28)
0.000
50–59
1374
921
2295
59.87%
0.16 (0.11–0.24)
0.000
60–69
285
215
500
57.00%
0.14 (0.09–0.22)
0.000
BMI
Underweight
67
34
101
66.34%
1.00
1.000
Normal
2178
1319
3497
62.28%
0.87 (0.58–1.32)
0.516
Obese
1190
629
1819
65.42%
1.02 (0.67–1.55)
0.943
Marriage
Unmarried
16
5
21
76.19%
1.97 (0.73–5.35)
0.183
Married
3326
1930
5256
63.28%
1.00
1.000
Divorced
27
18
45
60.00%
0.79 (0.44–1.44)
0.446
Loss of spouse
66
29
95
69.47%
1.32 (0.85–1.05)
0.217
Education level
Illiterate
89
38
127
70.08%
1.38 (0.94–2.04)
0.100
Primary school
1824
1085
2909
62.70%
1.00
1.000
Middle school
1333
746
2079
64.12%
1.05 (0.94–1.18)
0.371
University or above
189
113
302
62.58%
0.94 (0.74–1.20)
0.617
Number of family members
1
36
16
52
69.23%
1.00
1.000
2
237
151
388
61.08%
0.70 (0.37–1.30)
0.257
3
1000
602
1602
62.42%
0.74 (0.41–1.34)
0.320
4
491
280
771
63.68%
0.78 (0.42–1.43)
0.421
5
1466
820
2286
64.13%
0.79 (0.44–1.44)
0.449
6
152
83
235
64.68%
0.81 (0.43–1.55)
0.533
7 and above
53
30
83
63.86%
0.69 (0.25–1.92)
0.48
Annual income
≤5000
104
41
145
71.72%
1.00
1.000
5001–20000
549
367
916
59.93%
0.81 (0.55–1.16)
0.249
20001–50000
2235
1248
3483
64.17%
0.86 (0.61–1.23)
0.418
50001–80000
450
258
708
63.56%
0.89 (0.61–1.30)
0.546
>80000
97
68
165
58.79%
0.78 (0.49–1.24)
0.299The prevalence ofH. pylori in the group with one member only (69.23%) was higher than that in the group with other members, without statistical difference. As for the association of prevalence and annual family income, in the six groups (with an average level of RMB 35890.95, approximately $US 5000), we found that individuals with an annual family income of RMB >80000 had the lowest risk of H. pylori infection (58.79%), whereas those with annual family income of RMB5000 or less had the highest risk of H. pylori infection (71.72%), and there was a significant difference between the groups (P
=
0.017). Moreover, our study showed that the higher annual family income was, the lower the prevalence of H. pylori, which is significant in test for trend (P
=
0.022). As for the education level, H. pylori infection is higher in illiterate (70.08%) and those who received university education had the lowest H. pylori infection rate (62.58%). But there were no significant associations seen for the subjects’ level of education in general (P
=
0.138).Regarding the body mass index (BMI) value, healthy people (BMI = 18.5 to 24.9) had lowestH. pylori infection rate (62.28%) while those underweight (BMI < 18.5) people had highest infection rate (66.34%), but there was no significant difference between the groups.There was no apparent association between theH. pylori infection and other social factors, such as marriage status (P
=
0.369).


## 3.2. Relationships betweenH. pyloriInfection and Dietary Factors, Smoking, and Drinking

The results suggest thatH. pylori infection increased for subjects who ate vegetable more than once a day (65.71%), compared to those who ate it less than every other day (64.71%, ) and every other day to once a day (63.19% P
=
0.309), and there was no difference in χ
2 for trend (P
=
0.562), as shown in Table 2.Table 2
Relationships between prevalence ofH. pylori infection and dietary-related factors.
Factors
No. of subjects in Hp positive group
No. of subjects in Hp negative group
Total no. of subjects
Prevalence of Hp
OR (95% CI)
P value
Frequency of eating vegetables
<Every other day
22
12
34
64.71%
1.00
1.000
Every other day-once a day
3114
1814
4928
63.19%
0.94 (0.46–1.89)
0.853
>Once a day
299
156
455
65.71%
1.05 (0.51–2.19)
0.844
Frequency of eating fruits
0
23
10
33
69.70%
1.00
1.000
<Every other day
3199
1851
5050
63.35%
0.64 (0.30–1.39)
0.261
Every other day-once a day
213
121
334
63.77%
0.72 (0.33–1.61)
0.427
Frequency of eating milk, egg, and meat
0
2
0
2
100.00%
1.00
1.000
<Every other day
3211
1863
5074
63.28%
1.38 (1.01–1.88)
0.039
Every other day-once a day
113
58
171
66.08%
1.35 (0.88–2.09)
0.172
>Once a day
109
61
170
64.12%
1.00
Frequency of eating beans
0
8
3
11
72.73%
1.00
1.000
<Every other day
3229
1874
5103
63.28%
1.00 (0.29–3.43)
0.997
Every other day-once a day
198
105
303
65.35%
0.81 (0.23–2.84)
0.746
Frequency of eating onion and garlic
0
11
6
17
64.71%
1.00
1.000
<Every other day
3271
1880
5151
63.50%
1.21 (0.46–3.19)
0.695
Every other day-once a day
146
92
238
61.34%
1.24 (0.45–3.37)
0.677
>Once a day
7
4
11
63.64%
0.84 (0.18–3.88)
0.823
Frequency of eating pickled foods
0
2175
1311
3486
62.39%
1.00
1.000
<Every other day
448
223
671
66.77%
0.87 (0.73–1.03)
0.103
Every other day-once a day
810
447
1257
64.44%
0.97 (0.85–1.11)
0.683
>Once a day
2
1
3
66.67%
1.12 (0.10–12.44)
0.923
Frequency of eating fried foods
0
3138
1826
4964
63.22%
1.00
1.000
<Every other day
294
155
449
65.48%
1.14 (0.93–1.40)
0.211
Every other day-once a day
3
1
4
75.00%
0.58 (0.08–4.14)
0.59
Frequency of eating hot foods
0
3242
1856
5098
63.59%
1.00
1.000
<Every other day
191
125
316
60.44%
0.90 (0.71–1.14)
0.375
Every other day-once a day
2
1
3
66.67%
1.15 (0.10–12.66)
0.911In contrast, the prevalence ofH. pylori was highest in subjects who never ate fruits (67.70%), compared to the lowest infection rate in those who ate fruits less than every other day (63.35%, P
=
0.45), and there was no significant difference in χ
2 for trend (P
=
0.786).Our study also showed that those who never ate milk, egg, or meat had 100% infection ofH. pylori and people who ate less than every other day had the lowest infection rate (63.28%, P
=
0.535). People who ate pickled food less than every other day had the highest infection (66.77%), while those who never ate pickled food had the lowest infection rate (62.39%, P
=
0.032).However, there was no apparent association betweenH. pylori infection and other dietary-related factors, such as beans consumption (P
=
0.625), onion and garlic use (P
=
0.926), eating fried foods (P
=
0.065), and hot food (P
=
0.526).Table3 shows that there was no association between the prevalence of H. pylori infection and the use of tobacco or alcohol (Table 3). But there was significant relationship observed between H. pylori infection and the amount of cigarettes which a person had been smoking per day. Our data showed that people smoking 1 to 10 cigarettes per day had significantly higher rate of H. pylori infection than people smoking 11 to 20 cigarettes (P
=
0.041).Table 3
Relationships between prevalence ofH. pylori infection and smoking and alcohol drinking.
Factors
No. of subjects in Hp positive group
No. of subjects in Hp negative group
Total
Prevalence
OR  (95% CI)
P value
Smoking
No. of cigarettes smoked per day
0
2691
1535
4226
63.68%
1.00
1.000
1–10
191
108
299
63.88%
0.86   (0.68–1.09)
0.218
11–20
509
298
807
63.07%
1.19   (1.01–1.40)
0.036
>20
44
41
85
51.76%
0.80   (0.52–1.23)
0.321
The period of smoking  (year)
0
2691
1535
4226
63.68%
1.00
1.000
0–10
186
105
291
63.92%
1.18   (0.92–1.52)
0.183
11–20
389
221
610
63.77%
1.14   (0.95–1.36)
0.152
>20
169
121
290
58.28%
0.88   (0.69–1.12)
0.286
Drinking
589
313
902
65.30%
Beer
15
14
29
51.72%
Beer consumption per day (mL/d)
0
3420
1968
5388
63.47%
1.00
1.000
0–200
4
4
8
50.00%
0.96   (0.23–4.04)
0.960
201–500
9
10
19
47.37%
2.17   (0.72–6.54)
0.170
>500
2
0
2
100.00%
0.58   (0.04–9.25)
0.699
The period of drinking beer (year)
0
3420
1968
5388
63.47%
1.00
1.000
0–10
10
9
19
52.63%
2.17   (0.72–6.54)
0.169
11–20
5
2
7
71.43%
0.77   (1.72–3.45)
0.734
>20
0
3
3
0.00%
1.74   (0.18–16.69)
0.633
Wine
577
301
878
65.72%
Wine consumption per day (g/d)
0
2858
1681
4539
62.97%
1.00
1.000
<250
480
248
728
65.93%
1.07   (0.90–1.25)
0.445
251–500
95
53
148
64.19%
0.96   (0.68–1.34)
0.791
>500
2
0
2
100.00%
The period of drinking wine  (year)
0
2858
1681
4539
62.97%
1.00
1.000
0–10
186
110
296
62.84%
1.16   (0.90–1.48)
0.250
11–20
275
136
411
66.91%
1.04 (0.85–1.29)
0.686
>20
116
55
171
67.84%
0.90 (0.66–1.23)
0.521


## 3.3. Relationships betweenH. pyloriInfection and Upper Gastroduodenal Diseases

The prevalence ofH. pylori infection in individuals with history of gastroenteral diseases (64.60%) was higher than those without a history of this disease (57.26%, P
=
0.000) (Table 4).Table 4
Relationships between prevalence ofH. pylori infection and history of digestive diseases.
Factors
No. of subjects in Hp positive group
No. of subjects in Hp negative group
Total no. of subjects
Prevalence of Hp
OR (95% CI)
P value
History of digestive diseases
501
374
875
57.26%
0.71 (0.61–0.82)
0.000
Gastroenteritis
324
262
586
55.29%
0.67 (0.57–0.80)
0.000
Peptic ulcer
91
87
178
51.12%
0.57 (0.42–0.76)
0.000
Esophagitis
53
32
85
62.35%
0.95 (0.61–1.49)
0.838
Hepatitis
73
46
119
61.34%
0.91 (0.63–1.33)
0.636


## 3.4. Logistic Regression Model Analysis forH. pylori Infection

Thirty-six variables possibly related toH. pylori infection were assessed by using univariate logistic regression models analysis. The prevalence of H. pylori infection had a positive correlation with gender (P
=
0.022), kipple food (P
=
0.012), frequency of eating pickled food (P
=
0.052), frequency of eating fried foods (P
=
0.036), and digestive diseases (P
=
0.000), and negative correlation with factors of age (P
=
0.000), gastroenteral inflammation (P
=
0.000) and peptic ulcer (P
=
0.000) (Table 5(a)).Table 5
(a)  Risk factors forH. pylori infection. (b)  Logistic multivariate regression analysis of H. pylori infection.
(a)
Risk factors
B
Sx
Wald
P value
OR
95% CI
Gender
0.13
0.057
5.207
0.022
1.14
1.01–1.27
Age
-
0.037
0.004
78.336
0.000
0.96
0.95–0.97
Marriage
0.073
0.1
0.527
0.468
1.08
0.88–1.31
Education level
-
0.011
0.044
0.064
0.800
1.00
0.91–1.08
Family number
0.013
0.02
0.436
0.570
1.01
0.97–1.05
Annual income
0.000
0.000
0.212
0.748
1.00
1.00–1.00
Smoking
-
0.076
0.08
0.902
0.722
0.98
0.85–1.11
Number of cigarettes per day
0.003
0.003
0.934
0.347
1.00
0.99–1.01
The period of smoking
-
0.059
0.036
2.643
0.356
0.97
0.91–1.03
Alcohol
0.108
0.09
1.458
0.404
1.66
0.92–1.24
Beer  consumption per day
0.000
0.001
0.039
0.455
1.00
1.00–1.00
The period of drinking beer
-
0.033
0.037
0.768
0.220
0.97
0.93–1.02
Wine consumption per day
0.001
0.001
0.862
0.208
1.00
1.00–1.00
The period of drinking beer
0.003
0.007
0.177
0.333
1.00
0.99–1.01
Tea
-
0.043
0.137
0.099
0.831
0.97
0.74–1.27
Frequency of eating vegetables
0.002
0.003
0.488
0.485
1.00
0.99–1.01
Fruit
-
0.166
0.184
0.812
0.336
0.84
0.58–1.20
Frequency of eating fruits
-
0.001
0.005
0.011
0.918
1.00
0.99–1.01
Meat, milk, and eggs
-
2.527
3.536
0.511
Frequency of eating milk, egg, and meat
0.002
0.003
0.31
0.577
1.00
0.99–1.01
Bean
-
0.395
0.715
0.305
0.524
0.65
0.17–2.45
Frequency of eating beans
0.002
0.006
0.151
0.698
1.00
0.99–1.01
Onion and garlic
-
0.059
0.42
0.02
0.738
0.88
0.41–1.89
Frequency of eating onion and garlic
0.011
1.007
2.516
0.112
1.01
1.00–1.02
Kipper food
0.164
0.065
6.349
0.012
1.16
1.03–1.30
Frequency of eating pickled foods
0.006
0.003
3.774
0.052
1.01
1.00–1.02
Fried food
0.183
0.132
1.931
0.245
1.13
0.92–1.38
Frequency of eating fried foods
0.073
0.035
4.309
0.036
1.08
1.00–1.15
Scalding food
-
0.347
0.147
5.568
0.321
0.89
0.70–1.12
Frequency of eating hot foods
0.009
0.033
0.072
0.788
1.01
0.95–1.08
Digestive diseases
0.171
0.207
0.683
0.000
0.71
0.61–0.82
Gastroenteral inflammation
-
0.523
0.206
6.457
0.000
0.67
0.57–0.80
Peptic ulcer
-
0.64
0.217
8.706
0.000
0.57
0.42–0.76
Esophageal inflammation
-
0.047
0.226
0.044
0.838
0.95
0.61–1.49
Hepatitis
-
0.239
0.26
0.85
0.636
0.91
0.63–1.33
BMI
-
0.001
0.001
0.685
0.426
1.00
1.00–1.00
(b)
Risk factors
B
S.E.
Wald
P value
OR
95% CI
Gender
0,112
0.058
3.756
0.053
1.12
1.00–1.25
Age
-
0.04
0.004
88.709
0.000
0.96
0.95–0.97
Kipper food
0.142
0.115
1.524
0.217
1.15
0.92–1.44
Frequency of eating pickled foods
-
0.003
0.006
0.254
0.614
1.00
0.99–1.01
Frequency of eating fried foods
0.045
0.035
1.697
0.193
1.05
0.98–1.12
Digestive disease
0.131
0.155
0.705
0.401
1.14
0.84–1.54
Gastroenteritis
-
0.493
0.166
8.795
0.003
0.61
0.44–0.85
Peptic ulcer
-
0.51
0.193
7.001
0.008
0.6
0.41–0.88These eight factors then were introduced in the multivariate logistic regression analysis. Factors ultimately into the main effects model were independent factors forH. pylori infection. They were age (P
=
0.000), history of gastroenteritis (P
=
0.003), and history of peptic ulcer (P
=
0.008) (Table 5(b)).


## 4. Discussion

To our knowledge, the present study was the first to demonstrate risk factors ofH. pylori infection in Yangzhong country. However, five years ago, Shi et al. [9] also conducted a clinical trial investigating the prevalence of H. pylori infection in different areas, and compared to this previous study, our study found that the prevalence of H. pylori remained a continuously high rate in recent 5 years in Jiangsu province and that there were different risk factors related to H. pylori infection. The prevalence and onset of H. pylori in the general population are not clear since asymptomatic healthy individuals usually do not undergo endoscopic examination. Considering the large sample size and adjusting for various potential confounders, we believe that the results of this study accurately represent the risk factors of H. pylori infection in Yangzhong population.In the present study, we determined an overall prevalence and investigated the risk factors ofH. pylori in Yangzhong country. The prevalence of H. pylori infection varies all over the world, with less than 40% prevalence in developed countries and more than 80%–90% in developing countries [10]. The overall prevalence of H. pylori was 63.41% in Yangzhong city, similar to another previous study in Jiangsu Province by Shi et al. (62.07%) [9]. Since Yangzhong country is a high epidemic area of gastric cancer and lots of previous studies demonstrated that H. pylori infection can lead to gastric cancer [11, 12], our study was of great clinical importance. Recently, more attention has been given to the risk factors of H. pylori infection, such as gender, age, and socioeconomic status, but the result has still been controversial [13, 14].Yangzhong is a relatively enclosed country with limited population shifts. So the prevalence ofH. pylori infection is in its natural status. Thus, we randomly selected six regions in this country for the present study.


### 4.1. Prevalence ofH. pylori Infection and Social Factors

Malcolm et al. [15] reported that the H. pylori infection was associated with age, sex, and socioeconomic conditions. In a previous study [9], there was no relationship between H. pylori and gender, age in adults, but annual family income was an important risk factor. Ariizumi et al. [16] found that the H. pylori infection rate was associated with age, but there was no statistical difference between H. pylori infection with gender and BMI. In Dore et al. study [17], no statistical difference was observed between different socioeconomic groups and age groups.In our study, significant difference was observed in gender, age, and annual family income. We suggested that female had a higher infection rate than male. The explanation for this difference can only be speculative at this moment, being most probably related to the hormonal differences between the two genders, as recent studies identified an important role of oxytocin in the gastric evacuation rate (GER) [18]. Multivariate logistic regression model analysis also revealed that age was an important risk factor of H. pylori infection. The age group of 30–39 has shown a significant higher rate of H. pylori infection than other age groups. And the prevalence of H. pylori infection decreased with age. Previous studies showed that the infection rate was higher in childhood probably because people were usually infected with H. pylori when they were young [19]. A lower prevalence rate of H. pylori infection in the elderly has also been reported by others and two hypotheses have been proposed to explain these findings: H. pylori could have been present in a small number or low activation which might not have been detected. And H. pylori could have been present in the past, but was eliminated on account of the development of an unfavorable gastric environment with age. At the mean time, there is a progressive gastric migration in a proximal direction. As for the annual household income, we found that the prevalence increased when it was less than RMB5000 and the higher it was, the lower the prevalence of H. pylori, which was consistent with other reports [20, 21]. This might be related to the better living and sanitary conditions, with separate bedrooms for children.The risk factors forH. pylori infection also include more family members, lower education level, and abnormal BMI. We found that there was no statistical different between each group. Among these factors, higher educational level was slight but not significant decrease with the H. pylori infection, which may be explained by their difference kinds of occupation. We also found that normal body mass index had lowest infection rate and those underweight had the highest rate probably due to their decreased nutritional status and immunity.


### 4.2. Relationships betweenH. pyloriInfection and Dietary Factors

H. pylori infection could also be related to food and eating habits [22]. We investigated several dietary factors and found that eating kipper and fried food was positively associated with H. pylori infection. The consequence may be related to the way in which food is prepared, and dietary administration of salt may induce mucosal damage, such as diffuse erosion and degeneration, and destroy the mucosal barrier in the stomach. These changes in the gastric mucosa may be associated with an increased chance of persistent infection with H. pylori. Furthermore, salty food itself may be a source of H. pylori. The exact reason still needs to be further investigated.


### 4.3. Association betweenH. pylori and Drinking and Smoking

Two Japanese studies reported that smoking is negatively related toH. pylori infection [23, 24], but another study from Northern Ireland reported a positive relationship [25]. Other studies [26–29] found no relationship between smoking and H. pylori infection.In our study, there was no association between the prevalence ofH. pylori infection and the use of tobacco. And no significant relationship was observed between H. pylori infection and the period of time over which a person had been smoking, consistent with our previous study [9]. But in the present study, there was significant relationship observed between H. pylori infection and the amount of cigarettes smoked per day. Our data showed that people smoking 1 to 10 cigarettes per day had significantly higher rate of H. pylori infection than people smoking 11 to 20 cigarettes (P
=
0.041), suggesting that the risk of H. pylori infection decreased with cigarette consumption per day.The observed association of smoking with activeH. pylori infection may result from various mechanisms with partly antagonistic effects on the risk of infection. Potentially relevant effects of smoking include an increase in acid and pepsin secretion and changes in gastric motility, prostaglandin synthesis, gastric mucosal blood flow, and mucus secretion [30].As for drinking, our study showed that those who never drank beer had slightly higher rate ofH. pylori infection than people who consumed mild and moderate beverage. Meanwhile, people never drinking wine had lower incidence of H. pylori infection. However, the difference has no significance.Several previous studies have found the relation betweenHelicobacter pylori infection and alcohol consumption. Most of them did not find a significant association [31–35]. Interestingly, Brenner et al. [36] suggested a major protective effect of alcohol at moderate and high consumption but not at low consumption. Alcoholic beverages may directly and indirectly affect gastric mucosa, gastric acid secretion [37], and gastric emptying [38], leading to living condition changes of H. pylori in the stomach. In particular, moderate alcohol consumption might invigorate mucosal defense by its effects on prostaglandins [39]. Last, alcoholic beverages are known to have strong direct antibacterial activity [40–42].But our study showed that there was no association between the prevalence ofH. pylori infection and the use of alcohol, due to small sample size and heterogeneity between different groups. Besides consumption beverage, we also addressed other more details such as the type of alcoholic consumed and history of alcohol consumption. However there was no significant founding. Further studies involving larger numbers of subjects and multicenters should address more detailed additional factors and potential interactions between alcohol consumption and other factors that might affect active H. pylori infection.


### 4.4. Relationships betweenH. pyloriInfection and Digestive Diseases

Shi et al. [9] found that there was no association between H. pylori infection and histories of upper gastrointestinal diseases. However, our present study showed that there was no association between H. pylori infection and hepatitis and esophagitis, but a positive correlation was found between peptic ulcer and gastroenteritis. The data were confirmed by multivariate logistic regression analysis.H. pylori is motile, even in the highly viscous mucus layer. This may allow the organisms to evade both gastric motility and peristalsis, and also to some extent gastric acidity. Although it is motile, it also may adhere to the gastric mucosa through specific adhesion mechanisms. The secretion of large amounts of urease results in any urea in the environment being converted into ammonia-with the result that the intense acidity of the stomach may be ameliorated in the microenvironment surrounding the bacterium.About 50% ofH. pylori strains produce cytotoxins, of which some have been specifically linked to active gastritis and peptic ulceration. These cytotoxins can cause local inflammation, though other secretions by the organism, such as proteases and phospholipases, can attack and damage mucosal cell membranes. Weakening the gastric-mucosal barrier permits back-diffusion of hydrogen ions resulting in further tissue injury, as well as causing local immune responses to the organism.


## 4.1. Prevalence ofH. pylori Infection and Social Factors

Malcolm et al. [15] reported that the H. pylori infection was associated with age, sex, and socioeconomic conditions. In a previous study [9], there was no relationship between H. pylori and gender, age in adults, but annual family income was an important risk factor. Ariizumi et al. [16] found that the H. pylori infection rate was associated with age, but there was no statistical difference between H. pylori infection with gender and BMI. In Dore et al. study [17], no statistical difference was observed between different socioeconomic groups and age groups.In our study, significant difference was observed in gender, age, and annual family income. We suggested that female had a higher infection rate than male. The explanation for this difference can only be speculative at this moment, being most probably related to the hormonal differences between the two genders, as recent studies identified an important role of oxytocin in the gastric evacuation rate (GER) [18]. Multivariate logistic regression model analysis also revealed that age was an important risk factor of H. pylori infection. The age group of 30–39 has shown a significant higher rate of H. pylori infection than other age groups. And the prevalence of H. pylori infection decreased with age. Previous studies showed that the infection rate was higher in childhood probably because people were usually infected with H. pylori when they were young [19]. A lower prevalence rate of H. pylori infection in the elderly has also been reported by others and two hypotheses have been proposed to explain these findings: H. pylori could have been present in a small number or low activation which might not have been detected. And H. pylori could have been present in the past, but was eliminated on account of the development of an unfavorable gastric environment with age. At the mean time, there is a progressive gastric migration in a proximal direction. As for the annual household income, we found that the prevalence increased when it was less than RMB5000 and the higher it was, the lower the prevalence of H. pylori, which was consistent with other reports [20, 21]. This might be related to the better living and sanitary conditions, with separate bedrooms for children.The risk factors forH. pylori infection also include more family members, lower education level, and abnormal BMI. We found that there was no statistical different between each group. Among these factors, higher educational level was slight but not significant decrease with the H. pylori infection, which may be explained by their difference kinds of occupation. We also found that normal body mass index had lowest infection rate and those underweight had the highest rate probably due to their decreased nutritional status and immunity.


## 4.2. Relationships betweenH. pyloriInfection and Dietary Factors

H. pylori infection could also be related to food and eating habits [22]. We investigated several dietary factors and found that eating kipper and fried food was positively associated with H. pylori infection. The consequence may be related to the way in which food is prepared, and dietary administration of salt may induce mucosal damage, such as diffuse erosion and degeneration, and destroy the mucosal barrier in the stomach. These changes in the gastric mucosa may be associated with an increased chance of persistent infection with H. pylori. Furthermore, salty food itself may be a source of H. pylori. The exact reason still needs to be further investigated.


## 4.3. Association betweenH. pylori and Drinking and Smoking

Two Japanese studies reported that smoking is negatively related toH. pylori infection [23, 24], but another study from Northern Ireland reported a positive relationship [25]. Other studies [26–29] found no relationship between smoking and H. pylori infection.In our study, there was no association between the prevalence ofH. pylori infection and the use of tobacco. And no significant relationship was observed between H. pylori infection and the period of time over which a person had been smoking, consistent with our previous study [9]. But in the present study, there was significant relationship observed between H. pylori infection and the amount of cigarettes smoked per day. Our data showed that people smoking 1 to 10 cigarettes per day had significantly higher rate of H. pylori infection than people smoking 11 to 20 cigarettes (P
=
0.041), suggesting that the risk of H. pylori infection decreased with cigarette consumption per day.The observed association of smoking with activeH. pylori infection may result from various mechanisms with partly antagonistic effects on the risk of infection. Potentially relevant effects of smoking include an increase in acid and pepsin secretion and changes in gastric motility, prostaglandin synthesis, gastric mucosal blood flow, and mucus secretion [30].As for drinking, our study showed that those who never drank beer had slightly higher rate ofH. pylori infection than people who consumed mild and moderate beverage. Meanwhile, people never drinking wine had lower incidence of H. pylori infection. However, the difference has no significance.Several previous studies have found the relation betweenHelicobacter pylori infection and alcohol consumption. Most of them did not find a significant association [31–35]. Interestingly, Brenner et al. [36] suggested a major protective effect of alcohol at moderate and high consumption but not at low consumption. Alcoholic beverages may directly and indirectly affect gastric mucosa, gastric acid secretion [37], and gastric emptying [38], leading to living condition changes of H. pylori in the stomach. In particular, moderate alcohol consumption might invigorate mucosal defense by its effects on prostaglandins [39]. Last, alcoholic beverages are known to have strong direct antibacterial activity [40–42].But our study showed that there was no association between the prevalence ofH. pylori infection and the use of alcohol, due to small sample size and heterogeneity between different groups. Besides consumption beverage, we also addressed other more details such as the type of alcoholic consumed and history of alcohol consumption. However there was no significant founding. Further studies involving larger numbers of subjects and multicenters should address more detailed additional factors and potential interactions between alcohol consumption and other factors that might affect active H. pylori infection.


## 4.4. Relationships betweenH. pyloriInfection and Digestive Diseases

Shi et al. [9] found that there was no association between H. pylori infection and histories of upper gastrointestinal diseases. However, our present study showed that there was no association between H. pylori infection and hepatitis and esophagitis, but a positive correlation was found between peptic ulcer and gastroenteritis. The data were confirmed by multivariate logistic regression analysis.H. pylori is motile, even in the highly viscous mucus layer. This may allow the organisms to evade both gastric motility and peristalsis, and also to some extent gastric acidity. Although it is motile, it also may adhere to the gastric mucosa through specific adhesion mechanisms. The secretion of large amounts of urease results in any urea in the environment being converted into ammonia-with the result that the intense acidity of the stomach may be ameliorated in the microenvironment surrounding the bacterium.About 50% ofH. pylori strains produce cytotoxins, of which some have been specifically linked to active gastritis and peptic ulceration. These cytotoxins can cause local inflammation, though other secretions by the organism, such as proteases and phospholipases, can attack and damage mucosal cell membranes. Weakening the gastric-mucosal barrier permits back-diffusion of hydrogen ions resulting in further tissue injury, as well as causing local immune responses to the organism.


## 5. Conclusion

In conclusion, the prevalence ofH. pylori infection was 63.41% in the populations of Yangzhong country, Jiangsu province, which is also a region of high-risk gastric cancer in China. The prevalence of H. pylori infection was linked to sex, age, kipper food, frequency of eating kipper foods and fried food, peptic ulcer, and gastroenteritis. The relationship between H. pylori infection and other risk factors, such as upper gastrointestinal symptoms and some health habits, is still to be investigated.


## Conflict of Interests

The authors declare that there is no conflict of interests regarding the publication of this paper.



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*Source: 481365-2014-01-14.xml*