Incidence and Prevalence of Microscopic Colitis Between 2001 and 2016: A Danish Nationwide Cohort Study

Epidemiological studies suggest an increasing global incidence of microscopic colitis, including collagenous colitis and lymphocytic colitis. We aimed to investigate the incidence and prevalence of microscopic colitis in Denmark.

In a nationwide cohort study, we included all incident patients with a recorded diagnosis of collagenous colitis or lymphocytic colitis in the Danish Pathology Register between 2001 and 2016.

A total of 14 302 patients with microscopic colitis-8437 [59%] with collagenous and 5865 [41%] with lymphocytic colitis-were identified during the study period. The prevalence in December 2016 was estimated to be 197.9 cases per 100 000 inhabitants. Microscopic colitis was more prevalent among females (n = 10 127 [71%]), with a mean annual incidence of 28.8, compared with 12.3 per 100 000 person-years among males. The overall mean incidence during the study period was 20.7 per 100 000 person-years. Mean age at time of diagnosis was 65 years (standard deviation [SD]:14) for microscopic colitis, 67 [SD:13] for collagenous colitis, and 63 [SD:15] for lymphocytic colitis. The overall incidence increased significantly from 2.3 cases in 2001 to 24.3 cases per 100 000 person-years in 2016. However, the highest observed incidence of microscopic colitis was 32.3 cases per 100 000 person-years in 2011. Large regional differences were found, with the highest incidence observed in the least populated region.

The incidence of microscopic colitis in Denmark has increased 10-fold during the past 15 years and has now surpassed that of Crohn's disease and ulcerative colitis. However, incidence has stabilised since 2012, suggesting that a plateau has been reached.