Ethnic distribution of microscopic colitis in the United States

Background: A large electronic database of histopathology reports was used to study the ethnic distribution of microscopic colitis in the United States. Methods: Miraca Life Sciences is a nation-wide pathology laboratory that receives biopsy specimens submitted by 1500 gastroenterologists distributed throughout the United States. In a case-control study, the prevalence of microscopic colitis in 4 ethnic groups (East Asians, Indians, Hispanics, and Jews) was compared with that of all other ethnic groups (composed of American Caucasians and African Americans), serving as reference group. Results: A total of 11,706 patients with microscopic colitis were included in the analysis. In all ethnic groups alike, microscopic colitis was more common in women than men (78% versus 22%, odds ratio 3.40, 95% confidence interval 3.26-3.55). In all ethnic groups, the prevalence of microscopic colitis showed a continuous age-dependent rise. Hispanic patients with microscopic colitis were on average younger than the reference group (59.4 ± 16.2 years versus 64.2 ± 13.8 years, P < 0.001). Jewish patients with microscopic colitis were slightly older than the reference group (65.6 ± 13.4 years, P 0.015). Compared with the reference group (prevalence 1.20%), microscopic colitis was significantly less common among patients of Indian (prevalence 0.28%, odds ratio 0.32, 95% confidence interval 0.13-0.65), East Asian (0.22%, 0.19, 0.14-0.26), or Hispanic decent (0.48%, 0.40, 0.36-0.45) and significantly more common among Jewish patients (1.30%, 1.10, 1.01-1.21). Conclusions: Microscopic colitis shows striking variations of its occurrence among different ethnic groups. Such variations could point at differences in the exposure to environmental risk factors.