H. pylori and gastric cancer: the Asian enigma.

The actual distribution of Helicobacter pylori infection and its related diseases in various Asian countries is controversial. Only limited information is available regarding this issue. We discuss the etiological role of H. pylori in gastric cancer through the Asian experience. Seroprevalence of H. pylori infection in asymptomatic subjects and the annual incidence rate of gastric cancer per 100,000 in various Asian countries are summarized from literature reviews and World Health Organization statistics, respectively. There is a large intercountry variation in incidence of gastric cancer and H. pylori seroprevalence among Asian countries. There is a strong link between H. pylori infection and gastric cancer in many countries, such as Japan. By contrast, the prevalence of H. pylori infection is high in some countries, including India and Bangladesh, but low gastric cancer rates have been reported. These disparate observations represent the Asian enigma. Factors that may influence the etiology of gastric cancer include the genetic diversity of the infecting H. pylori strains and differences in the host genetic background in various ethnic groups, including gastric acid secretion and genetic polymorphisms in proinflammatory cytokines. These factors, in addition to environmental factors, such as personal hygiene and dietary habits, reflect the multifactorial etiology of gastric cancer.