Helicobacter pylori is present in approximately half the population of the world. It can exist innocuously for decades but is strongly implicated in the development of gastrointestinal disorders and cancers. In 13 September New England Journal of Medicine Naomi Uemura and colleagues from the Kure Kyosai Hospital, Kure, Japan examined 1,526 patients who had duodenal ulcers, gastric ulcers, gastric hyperplasia or nonulcer dyspepsia to ascertain how exposure to H. pylori related to incidence of cancer.

The patients were tested for an average of eight years for the presence of H. pylori. In all, 1,246 of the subjects were infected, leaving 280 who were not. The patients also underwent endoscopy at the start of the study, and then again between one and three years later.

Gastric cancer developed in 36 (2.9%) of those infected with H. pylori, compared with none of the uninfected patients. Significantly, the cancer also did...