Inverse Association between Helicobacter pylori Gastritis and Microscopic Colitis

Background: Inflammatory bowel disease is known to be inversely associated with Helicobacter pylori infection of the upper gastrointestinal tract. We hypothesized that a similar inverse association also applied to microscopic colitis. Methods: The associations between microscopic colitis and presence of H. pylori-positive chronic active gastritis (CAG), H. pylori-negative CAG, intestinal metaplasia, or gastric atrophy were expressed as odds ratios with their 95% confidence intervals. Multivariate logistic regression analyses were used to adjust these associations for sex, age, percentage residents per ZIP code with white, black, Hispanic, or Asian ethnicity, percentage with college education, average housing values, annual income, and population size of individual ZIP codes. Results: H. pylori-positive CAG was less common among patients with than without microscopic colitis (odds ratio 0.61; 95% confidence interval, 0.52-0.70). Intestinal metaplasia also occurred less frequently among patients with than without microscopic colitis (0.75, 0.65-0.86). These inverse associations remained unaffected by adjustments for parameters of ethnicity and socioeconomic status. In contradistinction with H. pylori-positive CAG, H. pylori-negative CAG was more common in patients with than without microscopic colitis (1.54, 1.17-1.97). Conclusions: H. pylori infection and microscopic colitis are inversely associated. This observation is consistent with similar inverse associations found between H. pylori and inflammatory bowel disease. These relationships may provide clues about the yet unknown etiology of microscopic colitis.