Decreasing incidence of inflammatory bowel disease in Eastern Canada: a population database study

Background: Nova Scotia has one of the highest incidences of inflammatory bowel disease (IBD) in the world. We wished to determine trends of IBD over time. Methods: All Provincial residents have government provided health insurance and all interactions with the hospital, and physician billing systems, are captured on an administrative database. We used a validated measure to define incident cases of Crohn's (CD), ulcerative colitis (UC) and undifferentiated IBD (IBDU). Incidence rates of these diseases for the years 1996-2009 were calculated. Results: Over the study period, 7,153 new cases of IBD were observed of which 3,046 cases were categorized as CD (42.6%), 2,960 as UC (41.4%) and 1,147 as IBDU (16.0%). Annual age standardized incidence rates were very high but have declined for CD from 27.4 to 17.7/100,000 population and for UC from 21.4 to 16.7/100,000. The decline was seen in all age groups and both genders. The decrease was not explained by a small increase in IBDU. Conclusion: The incidence of CD and UC are decreasing in Nova Scotia. If replicated elsewhere this indicates a reversal after a long period of increasing occurrence of IBD. This has implications for both epidemiology and health planning.