Aim: To describe the development in incidence, disease localization, activity, surgery and prognosis in two Danish paediatric population-based inflammatory bowel disease (IBD) cohorts comparing the time periods 1962-1987 (period I) and 1998-2006 (period II).
Materials and methods: Incident IBD patients below 15 years of age were included. Disease localization was classified according to the Montreal classification for ulcerative colitis (UC) patients and into small bowel, large bowel and small and large bowel combined for Crohn's disease (CD) patients. Disease activity and surgery in the first 2 years after diagnosis were assessed. Standardized cancer incidence rates and standardized mortality rates were calculated.
Results: One hundred and nineteen IBD patients (77 UC and 42 CD) were included. Comparing periods II and I, the incidence rate ratios were 0.81 [95% confidence interval (CI): 0.5-1.4] and 15.6 (95% CI: 7.5-32.7) in UC and CD, respectively. The number of UC patients with extensive disease (E3) increased from period I to II (46.7 vs. 94.1%, P<0.001). No colectomies were performed in UC patients in period II compared with nine in period I (P = 0.13) within the first 2 years after diagnosis. For patients diagnosed in period I, the standardized cancer incidence rate for UC was 37.9 (95% CI: 4.6-136.7) after a median follow-up period of 26 years.
Conclusion: We found a significant 15-fold increase in the incidence of CD and a significant increase in the number of UC patients with extensive disease in period II compared with period I. After a median follow-up time of 26 years, a possible increased risk of colorectal cancer in UC patients was detected.