The Epidemiology of Microscopic Colitis in Olmsted County, Minnesota: Population-Based Study From 2011 to 2019

Epidemiologic studies from Europe and North America have reported an increasing incidence of microscopic colitis (MC) in the late 20th century, followed by a plateau. This population-based study assessed recent incidence trends and the overall prevalence of MC over the past decade.

Residents of Olmsted County, MN, diagnosed with collagenous colitis (CC) or lymphocytic colitis (LC) between January 1, 2011, and December 31, 2019 were identified using the Rochester Epidemiology Project. Clinical variables were abstracted by chart review. Incidence rates were age- and sex-adjusted to the 2010 US population. Associations between incidence and age, sex, and calendar periods were evaluated using Poisson regression analyses.

A total of 268 incident cases of MC were identified with a median age at diagnosis of 64 years (range, 19-90 y); 207 (77%) were women. The age- and sex-adjusted incidence of MC was 25.8 (95% CI, 22.7-28.9) cases per 100,000 person-years. The incidence of LC was 15.8 (95% CI, 13.4-18.2) and CC was 9.9 (95% CI, 8.1-11.9) per 100,000 person-years. A higher MC incidence was associated with increasing age and female sex (P < .01). There was no significant trend in age- and sex-adjusted incidence rate over the study period (P = .92). On December 31, 2019, the prevalence of MC, LC, and CC (including cases diagnosed before 2011) was 246.2, 146.1, and 100.1 per 100,000 persons, respectively.

The incidence of MC and its subtypes was stable between 2011 and 2019, but its prevalence was higher than in previous periods. The incidence of MC continues to be associated with increasing age and female sex.