Abstract ID: A4
1. Gastroenterology, Hepatology and Nutrition, Children's Hospital of Eastern Ontario, Ottawa, ON, Canada; 2. Univ Calgary, Calgary, AB, Canada; 3. Medicine, University of Calgary, Calgary, AB, Canada; 4. Medicine and Community Health Sciences, University of Calgary, Calgary, AB, Canada; 5. Children's Hospital of Eastern Ontario, Ottawa, ON, Canada; 6. University of Calgary, Calgary, AB, Canada; 7. University of British Columbia, Vancouver, BC, Canada; 8. University of British Columbia, Vancouver, BC, Canada
Background: Asthma and the inflammatory bowel diseases (IBD) both result from complex gene-environment interactions and share genetic and environmental risk factors.
Aims: To examine the association between asthma and the subsequent development of Crohn’s disease (CD) or ulcerative colitis (UC).
Methods: We performed a population-based case-control study using health administrative data from the province of Alberta. Incident cases of CD and UC were identified using a validated algorithm based on ICD9 (CD 555; UC 556) and ICD10 codes (CD K50; UC K51). An 8-year washout period was used to distinguish incident from prevalent cases for individuals ≥10 years of age at IBD diagnosis; a 3-year washout period was used for those <10 years of age. Controls were derived from an age-stratified random sample of 10% of Albertans. The diagnosis of asthma was confirmed using a validated algorithm (ICD9 493; ICD10 J45). The odds of a asthma preceding the diagnosis of either CD (n=3,087) or UC (n=2,377) was compared to the odds of diagnosis of asthma among those without IBD (n=402,800) using logistic regression. Effect measure modification by age at diagnosis of IBD as defined by the Montreal Classification (≤16 years, 17-40 years, or >40 years) was evaluated using a likelihood ratio test. Age-stratified models are presented in the presence of effect measure modification. Logistic regression models were adjusted for age at IBD diagnosis (in the absence of effect measure modification), sex, rural/urban environment, and quintile of median income for individuals living in a dissemination area. A sensitivity analysis was conducted in which the diagnosis of asthma could either precede or follow the diagnosis of IBD.
Results: A diagnosis of asthma was associated with increased odds of incident CD (adjusted OR 1.45, 95% CI 1.31 to 1.60) with no effect modification by age at diagnosis (p=0.42). Effect modification by age at diagnosis was observed for UC (p=0.01). Asthma was associated with ulcerative colitis diagnosed at ≤16 years of age (adjusted OR 1.49, 95% CI 1.08 to 2.07) and >40 years of age (adjusted OR 1.57, 95% CI 1.31 to 1.89). There was no association between asthma and UC among individuals diagnosed between ages 17 and 40 (OR 1.05, 95% CI 0.86 to 1.26). Results were consistent in a sensitivity analysis that allowed the diagnosis of asthma to precede or follow the diagnosis of IBD.
Conclusions: Asthma is associated with an increased risk of CD, as well as early- and late-onset UC. This association requires confirmation and investigation into potential preventative strategies to reduce IBD risk, as well as identify individuals with chronic gastrointestinal symptoms who should be investigated for IBD.