Issue 23

Clinical Question

Are incidence rates of IBD dissimilar between rural and urban residential areas in Canada?

Editor’s Bottom Line

Rural residence in early childhood is associated with a lower incidence of IBD later in life.

Reference

Benchimol EI, Kaplan GG, Otley AR, et al. Rural and urban residence during early life is associated with risk of inflammatory bowel disease: a population-based inception and birth cohort study. Am J Gastroenterol. 2017 Sep;112(9):1412–22. https://www.ncbi.nlm.nih.gov/pubmed/28741616

Synopsis

Using validated classification algorithms for Crohn’s disease (CD) and ulcerative colitis (UC), provincial administrative databases were searched for incident IBD cases. In addition to the main definition discriminating between rural and urban areas (MIZ*), 13 other definitions were also explored to assess sensitivity. Data were presented as sex-standardized incidence (per 100,000 patient-years) and incident rate ratios (IRR) using Poisson regression for the retrospective cohort study and birth cohort study, respectively.

At the time of IBD diagnosis, 6,662 people resided in rural communities versus 38,905 in urban areas. Incidence rates for CD in rural versus urban areas were 14.88 vs. 15.57 per 100,000 people and were not significantly different. Incidence rates for UC were significantly lower in rural versus urban areas (13.83 vs. 15.55 per 100,000 people). The protective impact of rural residence against IBD was strongest in those of age <10 years (IRR 0.58) and 10–17.9 years (IRR 0.72). The birth cohort (rural, 331; urban, 2,302) living in rural areas during the first 1–5 years of life had a low risk of IBD diagnosis later in life (IRR 0.75–0.78).

* MIZ, Metropolitan Area and Census Agglomeration Influenced Zones

Details

Study Design: Retrospective cohort study and a birth cohort study
Funding: Janssen Future Leaders in IBD Program, Canadian Institutes of Health Research (CIHR), and others
Allocation: n/a
Setting: Retrospective study: Alberta 1999–2008, Manitoba and Ontario 1999–2010, Nova Scotia 2000–2008
Birth cohort study: Alberta 1996–2010, Manitoba 1988–2010, Ontario 1991–2010
Level of Evidence: 2b (Oxford Levels of Evidence)

The summary and conclusion in this issue of E-mentoring in IBD pertains to the manuscript(s) being reviewed, and should be considered in the context of what is already known surrounding the topic and incorporated into practice as deemed appropriate by the individual learner.