Smoking behavior and risk of Helicobacter pylori infection, gastric atrophy and gastric cancer in Japanese.

Although many studies have shown that smoking is an established risk factor for gastric cancer, relatively few studies have investigated on which step smoking has effects in Helicobacter pylori (H. pylori) related gastric carcinogenesis. In this study we investigated the association of smoking with risk of three steps leading to gastric cancer: H. pylori infection, gastric atrophy, and gastric cancer. Among the participants who visited Aichi Cancer Center Hospital from year 2001 to 2005, 583 cases diagnosed as gastric cancer and age-and sex-frequency-matched 1,742 cancer free controls were sampled, from whom those without serum samples or without information about smoking habit were excluded, leaving 576 cases and 1,599 controls eligible for the analyses. Anti- H. pylori IgG antibody and serum pepsinogens (PG) were measured to detect H. pylori infection and gastric atrophy. Smoking status was asked by a self-administered questionnaire. The odds ratio (OR) of H. pylori infection, as well as the OR of gastric atrophy among the H. pylori seropositive controls was not significant for smokers. The age- and sex-adjusted OR of gastric cancer was significantly elevated relative to the subjects with gastric atrophy: OR=1.62 (95% confidence interval (CI), 1.19-2.22; P=0.002) for ever smokers and 2.52 (1.75-3.64; P<0.001) for current smokers, relative to never smokers. This study revealed that smoking behavior contributed to the increased risk of gastric carcinogenesis from gastric atrophy, and had little influence on H. pylori infection or gastric atrophy development.