The incidence of ulcerative colitis (UC) and Crohn's disease (CD) has increased during the 20th century in North America and Western Europe. However, there are conflicting reports whether the incidence has declined, stabilized or even continued to increase. No nationwide Danish data on the incidence of UC and CD exist after 1992, and therefore we studied the incidence of UC (1995 through 2011) and CD (1995 through 2012).
Based on data from the Danish National Patient Registry we identified patients recorded with a first time diagnosis of UC or CD in the study periods. Among these - patients were only included in the study as incident cases if they had at least one more discharge diagnosis of UC/CD or at least three subsequent outpatient visits.
We identified 17,500 patients with UC and 7863 patients with CD. The mean incidence rate for UC in 1995-1998 was 14.4 per 100,000 per year for women and 13.8 for men, increasing to 23.2 per 100,000 per year for women and 23.4 for men in the period of 2009-2011. The mean incidence rate for CD in 1995-1998 was 7.8 per 100,000 per year for women and 5.6 for men, increasing to 10.3 per 100,000 per year for women and 8.9 for men in the period of 2009-2012.
Based on nationwide Danish data from the last two decades, the incidence rates of UC and CD have continued to increase.