Gastric cancer is related to early Helicobacter pylori infection in a high-prevalence country

Background and Aims: Chile ranks fifth in the world among countries with the highest incidence of gastric cancer. The aim was to quantify the association between Helicobacter pylori infection and gastric cancer mortality at the county of residence. Methods: A cross-sectional household survey, a probability sample of the Chilean adult population, provided 2,615 participants in whom serum H. pylori IgG antibodies were measured (ELISA). The spatial pattern of 48,367 deaths due to gastric cancer which occurred from 1985 to 2002 was analyzed using a hierarchical Poisson regression model; 333 counties were categorized as low, medium, and high gastric cancer mortality with median gastric cancer death rates of 11.4, 19.1, and 26.0 per 100,000 inhabitants, respectively. The association between H. pylori positivity and gastric cancer mortality in the county of residence was assessed by multivariate Poisson regression for complex samples. Results: H. pylori prevalence was 73.0% [95% confidence intervals (CI), 70.0-76.01, higher in men [prevalence rate ratio (PRIZ), 1.1 (95% Cl, 1.01-1.20)], peaked at ages 45 to 64, and dropped after age 65. It was higher among residents in counties with high gastric cancer mortality (79.7%; 95% Cl, 76.4-82.6) compared to counties with low gastric cancer mortality (62.3%; 95% Cl, 53.8-70.2; corresponding PRR, 1.3; 95% Cl, 1.1-1.5); under age 24, H. pylori infection was 79.7% (95% CI, 72.2-85.6) versus 39.8% (95% Cl, 19.6-64.2) among residents in counties with high and low gastric cancer mortalities, respectively (PRR, 2.0; 95% CI, 1.1-3.7). Conclusions: The high prevalence of H. pylori at younger ages was associated with high gastric cancer mortality in the base population.