Incidence and Prevalence of Crohn's Disease and Ulcerative Colitis in Olmsted County, Minnesota From 1970 Through 2010.

BACKGROUND & AIMS: The incidence and prevalence of inflammatory bowel diseases (IBD) continue to increase worldwide. We sought to update incidence rates of Crohn's disease (CD) and ulcerative colitis (UC) in a well-defined United States population, calculating values for Olmsted County, Minnesota through 2010. We also calculated prevalence values.

METHODS: The resources of the Rochester Epidemiology Project were used to identify county residents who were diagnosed with IBD (CD or UC), based on previously set criteria. Those with new diagnoses of CD or UC between 1970 and 2010 were identified as incidence cases, and those meeting diagnostic criteria on January 1, 2011, were identified as prevalence cases. Incidence rates were estimated (adjusted for age and sex to the US white population in 2010). Trends in incidence based on age at diagnosis, sex, and year of diagnosis were evaluated by Poisson regression.

RESULTS: The incidence cohort included 410 patients with CD (51% female) and 483 individuals with UC (56% male). Median age of diagnosis was 29.5 years for persons with CD (range, 4-93 years) and 34.9 years for UC (range, 1-91 years). From 2000 through 2010, the adjusted annual incidence rate for CD was 10.7 cases per 100,000 person-years (95% confidence interval [CI], 9.1-12.3 person-years) and for UC was 12.2 per 100,000 (95% CI, 10.5-14.0 person-years). On January 1, 2011, there were 380 residents with CD, with an adjusted prevalence of 246.7 cases per 100,000 persons (95% CI, 221.7-271.8 cases per 100,000 persons), and 435 residents with UC, with an adjusted prevalence of 286.3 (95% CI, 259.1-313.5 cases per 100,000 persons). Male sex was significantly associated with a higher incidence rate of UC, and younger age was significantly associated with a higher incidence rate of CD.

CONCLUSIONS: Estimated incidence rates for UC and CD in Olmsted County are among the highest in the United States. Extrapolating the adjusted prevalence to the most recent US Census, there could be approximately 1.6 million persons in the United States with IBD.