Helicobacter pylori is thought to be involved in the pathogenesis of gastric cancer, but the time point at which it produces its effects (critical time) is unknown. We measured the serum level of H. pylori antibody in 787 gastric cancer patients and 1007 controls aged 20 to 69. Odds ratios for different gastric cancer types and stages were determined for each 10-year age class. The overall odds ratio for gastric cancer decreased with age, being 7.0 for those aged 20-29, 14.5 for those aged 30-39, 9.1 for those aged 40-49, 3.5 for those aged 50-59, and 1.5 for those aged 60-69 (trend in odds ratios: P < < < <0.01). However, there was no such age-dependent trend for early diffuse-type cancer; the odds ratios were 12.6, 4.0, 7.2, 6.5, and 18.5 respectively (P = = = =0.29). Early cancer tended to show higher seroprevalence than advanced cancer, especially in older subjects. No significant difference in seroprevalence was observed between diffuse and intestinal cancers within each age-class. Seroreversion must have occurred in the time interval between the critical time and the diagnosis of the cancer, especially in older patients. The age-dependent relationship between H. pylori and gastric cancer may be due to seroreversion, which itself may be independent of age. This age-independence indicates that prolonged exposure to H. pylori does not increase the magnitude of its influence on gastric carcinogenesis. Possible mechanisms through which H. pylori exerts pathogenic effects are continuous inflammation in adulthood and/or irreversible damage to gastric mucosa in childhood or the teenage years. Key words: Gastric cancer -Helicobacter pylori -Age -Early diffuse-type cancerMany studies have shown that Helicobacter pylori is related to gastric cancer.1-3) While cancer prevention trials focusing on the eradication of H. pylori have already been started, the critical timeframe (critical time), during which it produces its carcinogenic effect, has not been identified yet. Identification of this critical time is important because eradication of H. pylori after this time would have no preventive effect on the incidence of gastric cancer.To begin to determine the critical time, we investigated the relationship between gastric cancer and H. pylori with respect to age. Previous studies on the relationship between smoking and lung cancer have shown that the longer the exposure to smoking, the greater the magnitude of its effect on the incidence of lung cancer. 4,5) In a previous study on H. pylori and gastric cancer, we found a high odds ratio of 13.3 for those under 40 years of age, 6) and a meta-analysis showed that the relationship is stronger in the younger population.7) However, other variables, such as geographic region and ethnicity, certainly affect the incidence of gastric cancer by age-class. 8,9) We sought to more clearly separate the influence of age from these other variables by taking a large sample from within a relatively well defined geographic and ethnic region, which is something that previous studies have la...

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A case-control study was conducted to evaluate the relationship between smoking or drinking doses and risk for stomach cancer, and to clarify whether the relationship is dose-dependent or U-shaped. Smoking dose was categorized as 0, 1-399, 400-799, or 800+ + + + cigarette-years, and drinking dose as 0, occasional/0.1-134.9, 135-1349.9, or 1350 + + + + alcohol-years (ml of pure alcohol intake per day multiplied by years of drinking). Helicobacter pylori status was determined by serology for adjustment. Using logistic regression, the adjusted effects of smoking and drinking doses on risk for stomach cancer were calculated for both genders. Among male subjects, the odds ratios (95% confidence intervals (

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