The 'Costa Rican enigma' of Helicobacter pylori CagA and gastric cancer.

摘要

Helicobacter pylori infection is related to a variety of disorders, including gastritis, gastroduodenal ulcers, and gastric cancers. This bacterium, a study of which earned the 2005 Nobel Prize, inhabits over half of the world's population, whereas the prevalence of the infection varies between populations and between groups within the same population. The prevalence of gastric cancer seems to be associated with that of H. pylori infection. However, there are several paradoxical and enigmatic findings that go against the H. pylori-gastric cancer association. For example, while the prevalence of H. pylori infection is high in southern Africa (African enigma) and some countries in South and Southeast Asia (Asian enigma), the incidence of gastric cancer is low. In Costa Rica, the standardized incidence of gastric cancer ranges from 61% to 140%, while the incidence of H. pylori infection is constant. Selection bias, extremely limited access to health care, and a short life expectancy may explain the African enigma. However, Costa Ricans' life expectancy is fairly long (78 years), and most Costa Ricans have access to medical facilities. Various factors such as food, chemical exposure, and H. pylori infection have been studied for their involvement in the prevalence of gastric cancer in this nation. However,no clear-cut explanations have yet become available for this "Costa Rican enigma."