A population-based case control study of potential risk factors for IBD.

We aimed to pursue potential etiological clues to Crohn's disease (CD) and ulcerative colitis (UC) through a population-based case control survey study. Cases with CD (n = 364) and UC (n = 217), ages 18-50 yr were drawn from the population-based University of Manitoba IBD Research Registry. Potential control subjects were drawn from the population-based Manitoba Health Registry by age, gender, and geographic residence matching to the cases (n = 433). Subjects were administered a multiitem questionnaire. By univariate analysis, some of the variables predictive of CD included lower likelihood of living on a farm, of having drunk unpasteurized milk or having eaten pork, and UC patients were less likely to have drunk unpasteurized milk and to have eaten pork. On multivariate analysis, variables significantly associated with CD were being Jewish (OR = 4.32, 95% CI 1.10-16.9), having a first degree relative with IBD (OR = 3.07, 95% CI 1.73-5.46), ever having smoked (OR = 1.54, 95% CI, 1.06-2.25), living longer with a smoker (OR = 1.03, 95% CI, 1.01-1.04). Being a first generation Canadian (OR = 0.33, 95% CI, 0.17-0.62), having pet cats before age 5 (OR = 0.66, 95% CI, 0.46-0.96) and having larger families (OR = 0.87, 95% CI, 0.79-0.96) were protective against CD. For UC being Jewish (OR = 7.46, 95% CI, 2.33-23.89), having a relative with IBD (OR = 2.23, 95% CI, 1.27-3.9), and ever smoking (OR = 1.62, 95% CI, 1.14-2.32) were predictive. This study reinforced the increased risk associated with family history, being Jewish, and smoking history, however, a number of significant associations with CD and UC on univariate and multivariate analysis may support the "hygiene hypothesis" and warrant further exploration in prospective studies.