Alcohol drinking and gastric cancer risk: An evaluation based on a systematic review of epidemiologic evidence among the Japanese population

Background: We reviewed epidemiologic studies on the association between alcohol drinking and gastric cancer among the Japanese population. This report is one of a series of articles by our research group, which is evaluating the existing evidence concerning the association between health-related lifestyles and cancer. Methods: Original data were collected by searches of MEDLINE using PubMed, or searches of the Ichushi database, complemented with manual searches. Evaluation of associations was based on the strength of evidence and the magnitude of association, together with biological plausibility as evaluated previously by the International Agency for Research on Cancer. Results: Of the 11 cohort studies evaluated, nine showed no association between alcohol drinking and gastric cancer, and one study showed a strong positive association among men. All of 11 case-control studies found no association between alcohol drinking and gastric cancer. By anatomical subsites of gastric cancer, only three studies have evaluated the association between alcohol drinking and gastric cancer, and one cohort study found a positive association for cardia and upper-third gastric cancer in men. Few studies conducted among the Japanese population have made a detailed assessment of alcohol drinking, possible important confounding factors such as smoking and diet and anatomical subsites of gastric cancer. Conclusion: We conclude that epidemiologic evidence for an association between alcohol drinking and gastric cancer risk remains insufficient due to the methodological quality of studies that have been conducted among the Japanese population.