Original Contribution Population-based Prospective Study of the Combined Influence of Cigarette Smoking and Helicobacter pylori Infection on Gastric Cancer Incidence The Hisayama Study

The authors assessed the separate and joint influences of cigarette smoking and Helicobacter pylori infection on the development of gastric cancer in a population-based prospective study. A total of 1,071 Japanese men aged 40 years were followed up prospectively for 14 years (1998–2002). Compared with that for current nonsmokers, the multivariate-adjusted hazard ratios of gastric cancer for smokers of 1–9, 10–19, and 20 cigarettes per day were 1.36 (95 % confidence interval (CI): 0.50, 3.71), 1.93 (95 % CI: 1.01, 3.67), and 1.88 (95 % CI: 1.02, 3.43), respectively. The risk of gastric cancer increased steeply for subjects who had both a smoking habit and H. pylori infection compared with those who did not have both risk factors (hazard ratio 11.41, 95 % CI: 1.54, 84.67). If causal, the estimated population attributable fraction of gastric cancer for cigarette smoking was approximately half that for H. pylori infection (28.4 % vs. 56.2%). The overlap of the population attributable fractions for the 2 factors was 49.6%. Findings suggest that cigarette smoking and H. pylori infection are significant risk factors for gastric cancer in Japanese men, and the magnitude of their combined influence is considerable. cohort studies; Helicobacter pylori; smoking; stomach neoplasms Abbreviations: CI, confidence interval; HR, hazard ratio; PAF, population attributable fraction. A number of epidemiologic and clinical studies have demonstrated clear associations between cigarette smokin