Most studies concerning the clinical course in CD are retrospective or based on selected patient groups. Our aim was to assess the course of CD in a prospective population-based follow-up study and to identify possible prognostic risk factors for complications on the basis of information obtained at initial diagnosis.

From 1990–1994, a population-based cohort of 843 new cases of inflammatory bowel disease was recruited in South-Eastern Norway. The cohort was systematically followed up at 1, 5, and 10 years after diagnosis.

Of 237 patients classified as CD, 197 completed the 10 years of follow-up, 18 died, and 22 were lost to follow-up. The cumulative relapse rate during the first 10 years was 90% (95% confidence interval, 86%–94%), and the cumulative probability of surgery was 37.9% (95% confidence interval, 31.4%–44.4%). Terminal ileal location (P < .001), stricturing (P = .004), penetrating behavior (P < .001), and age younger than 40 years (P = .03) at diagnosis were independent risk factors for subsequent surgery. A total of 53% (n = 105) of the patients had developed stricturing or penetrating disease at 10 years. A large proportion of patients (44%) were in clinical remission during the last 5 years of follow-up.

The prognosis for CD seems better than previously reported. The probability of surgery was low, and fewer than expected developed complicated disease behavior. Nevertheless, the cumulative relapse rate of 90% and the finding of prognostic risk factors for subsequent surgery might call for attention to early effective medical treatment strategies.