Increased Incidence of Inflammatory Bowel Disease among Québec Patients with Airway Diseases

Abstract

Purpose: Inflammatory bowel disease (IBD) and airway diseases may be associated through common inflammatory pathways, genetic, and environmental factors. The prevalence of both Crohn's disease (CD) and ulcerative colitis (UC) seems to be increased among patients with airway diseases. Québec is the province with the second highest incidence and prevalence of IBD in Canada, and with a prevalence of asthma and chronic obstructive pulmonary disease (COPD) above the Canadian average. To date, there are no reports of an association between airway diseases and the incidence of IBD. We sought to compare the incidence of CD and UC in Québec patients with airway diseases, and in the general population. Methods: A population-based retrospective cohort study was conducted using the administrative health databases of the Province of Québec, Canada, a province with about 7 million inhabitants. Individuals with airway diseases, including asthma and COPD, were identified by the dispensation of three or more prescriptions for respiratory medication in a one-year period on at least two separate occasions. Individuals with IBD were identified using a validated case definition requiring at least one hospitalization or four physician claims with either a CD or UC diagnosis within a two-year period. Incident IBD cases were defined as individuals who had been free of IBD for at least two years prior to the two-year time span of the case definition, and who met the criteria in the year they were counted as incident. Incidence rates (IR) were calculated for the 2001-2007 period in the defined airway disease cohort and in the Québec general population, standardized by age and sex using the 2001 Québec Census population. Results: Among the 436,008 individuals with airway disease, 731 also had CD, and 526 had UC during a mean follow-up of 6.8 years. The mean age at diagnosis was 53.5 and 64.7 years for CD and UC, respectively. The IR was 25.2 CD and 14.9 UC cases/100,000 person-years (p-y) (Table). Compared to the Québec general population, the incidence among patients with airway diseases was more than 40% higher for both CD and UC. The CD IR was highest in the 20-29 year age group (33.8/100,000 p-y), and gradually decreased with increasing age (Table). The IR for UC was highest in the 55+ age group (24.5/100,000 p-y). The incidence rate ratio for females vs. males was 1.45 (95% CI 1.40-1.50) for CD and 1.02 (95% CI 0.98-1.07) for UC.Table: Table. Incidence of Crohn's disease and ulcerative colitis in patients with airway diseases, Québec 2001-2007*Conclusion: During 2001-2007, the incidence of both CD and UC in patients with airway disease was significantly higher than in the Québec general population. Women with airway disease were more likely to develop CD.