Tobacco smoking increases the risk for gastric adenocarcinoma among Helicobacter pylori-infected individuals.
BACKGROUND
The importance of tobacco smoking and Helicobacter pylori infection as risk factors in the development of gastric carcinoma was investigated through multivariate conditional logistic regression analysis in a nested case-control study.


METHODS
Blood samples and a questionnaire on smoking habits were collected from a cohort of 32,906 city residents during a health screening programme from 1974 to 1992. Fifty-six cases of gastric cancer and 224 matched controls were selected. The mean interval between screening and cancer diagnosis was 5.7 years. H. pylori infection was determined by IgG-serology. Occupation categorized into blue-collar workers, white-collar workers, self-employed and unknown occupation was included in the statistical analysis as an indicator of socio-economic status.


RESULTS
The proportion of current smokers was 61% among gastric cancer cases, versus 41% among controls. H. pylori seropositivity was present in 82% of the cases and 49% of the controls. In a multivariate model current smokers had an odds ratio (OR) of 2.2 (95% confidence interval (CI): 1.2-4.2). With different levels of tobacco consumption, smoking less than 20 g tobacco each day gave the OR of 2.1 (95% CI: 0.98-4.4), and the OR when smoking more than 20 g tobacco per day was 2.5 (95% CI: 1.1-5.6). The OR of H. pylori infection was 5.0 (95% CI: 2.2-11.2). Among H. pylori-seropositive citizens, current smoking was associated with an increased risk of 2.3 (95% CI: 1.1-4.7) compared with non-smoking H. pylori-positive persons.


CONCLUSIONS
Tobacco smoking and H. pylori are both risk factors in the development of gastric cancer, and tobacco smoking is still a risk factor among H. pylori-infected individuals. The risk of gastric cancer among H. pylori-infected current smokers is 11 times that of non-infected individuals not currently smoking.
Simán
J H
JH
Dept. of Medicine, Lund University, Malmö University Hospital, Sweden.
Forsgren
A
A
Berglund
G
G
Florén
C H
CH
D000230:Adenocarcinoma / Q000209:etiology*; D000328:Adult; D005260:Female; D016481:Helicobacter Infections / Q000150:complications*; D016480:Helicobacter pylori; D006801:Humans; D008297:Male; D008875:Middle Aged; D009790:Occupations; D016017:Odds Ratio; D012307:Risk Factors; D012907:Smoking / Q000009:adverse effects*; D013274:Stomach Neoplasms / Q000209:etiology*