The changing face of Crohn's disease: a population-based study of the natural history of Crohn's disease in Orebro, Sweden 1963-2005

Objective: Changes in medical therapy and surgery might have influenced the natural history of Crohn's disease (CD). Our aim was to explore the short-term outcome of CD and to specifically assess trends in disease phenotype, medications and surgery in the first five years from diagnosis. Material and methods: A population-based cohort comprising 472 CD patients diagnosed within the primary catchment area of orebro University Hospital 1963-2005 were identified retrospectively and described. Data on medication, surgery, progression in disease location and behavior, were extracted from the medical records. Patients were divided into three cohorts based on year of diagnosis. Results: The proportion of patients with complicated disease behavior five years after diagnosis decreased from 54.4% (95%CI, 43.9-65.6) to 33.3% (27.4-40.0) in patients diagnosed 1963-1975 and 1991-2005, respectively (p=0.002), whereas the proportion of patients progressing to complicated disease behavior was stable among those with non-stricturing, non-penetrating disease at diagnosis (p=0.435). The proportion of patients undergoing surgery decreased from 65.8% (55.4-76.0) to 34.6% (28.6-41.5) in patients diagnosed 1963-1975 and 1991-2005, respectively (p<0.001). The reduction in surgery preceded an increased use of immunomodulators and was explained by a decrease in surgery within three months from diagnosis (p=0.001). Conclusions: We observed a striking decrease in complicated disease behavior and surgery five years after CD diagnosis, the latter largely due to a decrease in early surgery. Our findings suggest that the introduction of new treatments alone does not explain the reduction in surgery rates, the increasing proportion of patients with inflammatory disease at diagnosis also play an important role.