Background: Epidemiological studies suggest an increasing global incidence of microscopic colitis, including collagenous colitis and lymphocytic colitis.
Aims: To investigate the incidence and prevalence of microscopic colitis in Denmark.
Methods: 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.
Results: A total of 14,302 microscopic colitis patients - 8,437 (59%) with collagenous and 5,865 (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 to 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 (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.
Conclusions: The incidence of microscopic colitis in Denmark has increased 10-fold during the last 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.
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