Update on the incidence and prevalence of Crohn's disease and ulcerative colitis in Olmsted County, Minnesota, 1940-2000.

BACKGROUND: We previously reported that the prevalence of Crohn's disease (CD) and ulcerative colitis (UC) in Olmsted County, Minnesota, had risen significantly between 1940 and 1993. We sought to update the incidence and prevalence of these conditions in our region through 2000.

METHODS: The Rochester Epidemiology Project allows population-based studies of disease in county residents. CD and UC were defined by previously used criteria. County residents newly diagnosed between 1990 and 2000 were identified as incidence cases, and persons with these conditions alive and residing in the county on January 1, 2001, were identified as prevalence cases. All rates were adjusted to 2000 US Census figures for whites.

RESULTS: In 1990-2000 the adjusted annual incidence rates for UC and CD were 8.8 cases per 100,000 (95% confidence interval [CI], 7.2-10.5) and 7.9 per 100,000 (95% CI, 6.3-9.5), respectively, not significantly different from rates observed in 1970-1979. On January 1, 2001, there were 220 residents with CD, for an adjusted prevalence of 174 per 100,000 (95% CI, 151-197), and 269 residents with UC, for an adjusted prevalence of 214 per 100,000 (95% CI, 188-240).

CONCLUSION: Although incidence rates of CD and UC increased after 1940, they have remained stable over the past 30 years. Since 1991 the prevalence of UC decreased by 7%, and the prevalence of CD increased about 31%. Extrapolating these figures to US Census data, there were approximately 1.1 million people with inflammatory bowel disease in the US in 2000.