The Rising Burden of Inflammatory Bowel Disease in Denmark Over Two Decades: A Nationwide Cohort Study

Background & aims: Shifts in epidemiological stages of inflammatory bowel disease (IBD) carry implications toward understanding IBD etiology and managing clinical care. We conducted a temporal analysis of the epidemiology of IBD between 1995 and 2016 in the Danish nationwide cohort.

Methods: We used the Danish registers to obtain data on demographics and IBD-related outpatient and inpatient contacts between 1995 and 2016. IBD diagnosis was defined as having ≥2 registrations related to Crohn's disease (CD) or ulcerative colitis (UC) within a 2-year period. We estimated overall and annual incidence rates and prevalence of CD and UC standardized with respect to age and sex.

Results: A total of 47,830 individuals met the criteria for IBD diagnosis, of which 33% were diagnosed with CD and 67% with UC. Between 1995 and 2016, the incidence rate (95% confidence interval) per 100,000 person-years rose from 9.1 (8.3-10.0) to 17.8 (16.8-19.0) for CD, and from 21.0 (19.8-22.3) to 28.4 (27.0-29.8) for UC. The highest increase in CD and UC incidence rates occurred in children and young adults, respectively. The prevalence of IBD doubled from 1995 to 2016; the greatest increase (2.5-fold) was in UC prevalence among individuals aged >40 years. During this period, the median age of the IBD population increased by 6 to 7 years.

Conclusions: In Denmark, the incidence and prevalence of IBD have increased during the last 2 decades. The IBD population is shifting toward an older age. These findings have implications towards understanding environmental shifts as well as preparing health care systems for an aging IBD population.