Age at establishment of Helicobacter pylori infection and gastric carcinoma, gastric ulcer, and duodenal ulcer risk.

Helicobacter pylori is an important risk factor for gastric cancer, gastric ulcer, and duodenal ulcer, yet most infected persons do not develop disease. We examined two correlates of acquisition age, sibship size and birth order, to evaluate the hypothesis that early life acquisition of H. pylori is a risk factor for the development of these illnesses. In earlier nested case-control studies of a cohort of Japanese American men in Hawaii, evidence of H. pylori infection was associated with the development of gastric cancer or gastric or duodenal ulceration during the subsequent period, 1968-1989. The present analysis included 102, 147, and 64 men who developed adenocarcinoma of the distal stomach, gastric ulcer, and duodenal ulcer, respectively, and a matched control for each. Sibship size and birth order data were analyzed as risk factors for development of these diseases. H. pylori-infected but not H. pylori-uninfected men from larger sibships (odds ratio, 2.06) and of higher birth order (odds ratio, 1.67) were at increased risk for developing gastric cancer. H. pylori- infected men but not uninfected men at higher birth order had increased risk of gastric (odds ratio, 1.64) but not duodenal ulcers. These data are consistent with the hypothesis that early life acquisition of H. pylori increases the risk of developing both gastric cancer and gastric ulcer but not duodenal ulcer.