A recent study notes an increasing incidence of and high prevalence of inflammatory bowel disease (IBD) in Ontario, Canada (Inflamm Bowel Dis 2014; 20: 1761-69).
This article notes that between 1999-2008, there was an increased incidence of IBD from 21.3 to 26.2 per 100,000. This affected most age groups less than 65 years, but increased most rapidly in children younger than 10 years (increased 9.7% per year). The highest incidence remained in adults aged 20 to 29 years. The overall prevalence in Ontario was estimated to be 1 in 200 overall, which is among the highest in the world. This study relied on a validated health administrative data consisting of all Ontario residents.
The potential for misclassification bias is discussed and the potential difficulties with administrative health data is detailed in three related editorials (pages 1777-79, 1780-81, 182-83). The editorials are helpful, in part, because a separate study in the same journal (Inflamm Bowel Dis 2014; 20: 1770-76) indicates that the incidence of Crohn’s disease and Ulcerative Colitis declined in Quebec between 2001-08. However, the authors of this study used less-rigorous methods and had a much shorter “washout” period (two years versus eight years).
At the end of the day, with conflicting studies, there remains some uncertainty with regard to IBD epidemiology. That being said, the first study notes that “75% of CD studies and 60% of UC studies had reported increased incidence in the adult populations.”
This leads back to the question of what environmental exposures are leading to these changes in incidence.
Bottomline: This article and the associated editorials helps highlight the difficulties of using administrative health data and why many data points are needed to assess the epidemiology of IBD. In all likelihood, the incidence of IBD is increasing.
Related blog post: Global increases in IBD incidence | gutsandgrowth