Trends in the incidence of gastric cancer in Japan and their associations with Helicobacter pylori infection and gastric mucosal atrophy

Background. Although age-adjusted mortality from gastric cancer has been decreasing in Japan, the crude incidence of gastric cancer shows a slight increase. Methods. We have observed trends in the incidence of gastric cancer by sex and 20-year age groups over the past two decades (1976-1996). Source data were obtained from the cancer statistics materials provided by the Research Group for Population-Based Cancer Registration in Japan. Simultaneously, we observed changes in the prevalence of Helicobacter pylori infection and in serological atrophy of the gastric mucosa, and compared the results with those involving changes hi the incidence of gastric cancer. Results. A slight decline was observed in all age groups over 40 years old, in both men and women, between 1986 and 1996. However, a marked decline in incidence was observed for those aged 20-39 years. The prevalence of H. pylori infection declined in both sexes between 1989 and 1998. The frequency of serological atrophy of the gastric mucosa significantly declined in all age groups between 1989 and 1996, with young age groups experiencing a more marked decrease. Conclusion. The marked decline in gastric cancer incidence observed in the young population will also begin to occur in the elderly population in the future.