Risk factors associated with progression to intestinal complications of Crohn's disease in a population-based cohort

Background And Aims We sought to assess the evolution of Crohn's disease behavior in an American population-based cohort. Methods Medical records of all Olmsted County, Minnesota residents who were diagnosed with Crohn's disease from 1970 to 2004 were evaluated for their initial clinical phenotype, based on the Montreal Classification. The cumulative probabilities of developing structuring and/or penetrating complications were estimated using the Kaplan-Meier method. Proportional hazards regression was used to assess associations between baseline risk factors and changes in behavior. Results Among 306 patients, 56.2% were diagnosed between the ages of 17 and 40 years. Disease extent was ileal in 45.1%, colonic in 32.0%, and ileocolonic in 18.6%. At baseline, 81.4% had nonstricturing nonpenetrating disease, 4.6% had stricturing disease, and 14.0% had penetrating disease. The cumulative risk of developing either complication was 18.6% at 90 days, 22.0% at 1 year, 33.7% at 5 years, and 50.8% at 20 years after diagnosis. Among 249 patients with nonstricturing, nonpenetrating disease at baseline, 66 changed their behavior after the first 90 days from diagnosis. Relative to colonic extent, ileal, ileocolonic, and upper GI extent were significantly associated with changes in behavior, whereas the association with perianal disease was barely significant. Conclusions In a population-based cohort study, 18.6% of patients with Crohn's disease experienced penetrating or stricturing complications within 90 days after diagnosis; 50% experienced intestinal complications 20 years after diagnosis. Factors associated with development of complications were the presence of ileal involvement and perianal disease.