Incidence and natural history of ulcerative colitis in the Uppsala Region of Sweden 2005-2009 - results from the IBD cohort of the Uppsala Region (ICURE).

Background And Aims: The incidence of ulcerative colitis (UC) increased during the 20th century in Western Europe and the North America, but there are conflicting reports whether the incidence has declined, stabilized or continued to increase. The aim of this study was to evaluate the incidence of UC in the Uppsala Region, Sweden.

Methods: All new UC patients in Uppsala County (305,381 inhabitants) were prospectively registered during 2005-2006 and the same for all new UC patients in the Uppsala Region (642,117 inhabitants) during 2007-2009. The extent and severity of disease according to the Montreal classification, relapse rates and surgery were assessed.

Results: 526 UC patients were included. The mean overall incidence for the time period was 20.0 (95% CI: 16.1-23.9) cases per 100,000 inhabitants. The incidence among children <17 years of age was 8.9 per 100,000. The extent at diagnosis was evenly distributed (E1: n=167, 32%, E2: n=161, 31%, E3: n=163, 31%). Half of the cases had moderate to severe symptoms (S1: n=269, 51%, S2: n=209, 40%, S3: n=45, 8.6%). 228 (43%) relapsed and 13 (2.5%) required colectomy during the first year. Children had a higher proportion of extensive disease vs adults (27/42 vs 136/484), but no increased risk for severe symptoms or colectomy.

Conclusion: In this prospective population-based study we found one of the highest incidences of UC in the world. The proportion of severe cases is comparable with historical data. The conclusion is that the nature of UC has not changed, only the incidence.