Increase in incidence and prevalence of inflammatory bowel disease in northern Denmark: a population-based study, 1978-2002.

Objectives: Although incidence rates of inflammatory bowel disease have been reported worldwide, few long-term population-based studies with current time-trend analyses exist. We therefore examined time trends in the incidence rate of inflammatory bowel disease in a 25-year study period, and estimated the prevalence in 2002. All patients diagnosed between 1978 and 2002 were included as incident cases (n=2,326) and all patients living in North Jutland County on 31 December 2002 were used to estimate prevalent cases (n=2,205).

Methods: Medical records of all patients diagnosed with ulcerative colitis and Crohn's disease in the North Jutland County Hospital Discharge Registry were reviewed to examine if the diagnostic criteria were fulfilled. Age-specific and gender-specific standardized incidence rates were calculated.

Results: For ulcerative colitis, incidence rates in women increased from 8.3 (95% confidence interval (CI): 6.7-9.9) in 1978-1982 to 17.0 (95% CI: 14.7-19.3) per 100,000 person-years in 1998-2002. The corresponding figures for men were 7.7 (95% CI: 6.1-9.3) and 16.7 (95% CI: 14.4-18.8) per 100,000 person-years. For Crohn's disease, the incidence rates in women increased from 4.1 (95% CI: 3.0-5.2) in 1978-1982 to 10.7 (95% CI: 8.8-12.5) per 100,000 person-years in 1998-2002. The corresponding figures for men were 3.2 (95% CI: 2.1-4.2) and 8.5 (95% CI: 6.9-10.2) per 100,000 person-years. The prevalence of ulcerative colitis and Crohn's disease was 294 and 151 per 100,000 inhabitants, respectively.

Conclusions: A marked and parallel increase was seen in both ulcerative colitis and Crohn's disease in both genders during the last 25 years, with a corresponding high prevalence of both diseases.