title: The prevalence and geographic distribution of Crohn's disease and ulcerative colitis in the United States.
abstract: OBJECTIVE
  Previous US studies of inflammatory bowel disease (IBD) prevalence have sampled small, geographically restricted populations and may not be generalizable to the entire nation. This study sought to determine the prevalence of Crohn's disease (CD) and ulcerative colitis (UC) in a large national sample and to compare the prevalence across geographic regions and other sociodemographic characteristics.
  
  
  METHODS
  We analyzed the health insurance claims for 9 million Americans, pooled from 87 health plans in 33 states, and identified cases of CD and UC using diagnosis codes. Prevalence was determined by dividing the number of cases by the number of persons enrolled for 2 years. Logistic regression was used to compare prevalence estimates by geographic region, age, sex, and insurance type (Medicaid vs commercial).
  
  
  RESULTS
  The prevalence of CD and UC in children younger than 20 years was 43 (95% confidence interval [CI], 40-45) and 28 (95% CI, 26-30) per 100,000, respectively. In adults, the prevalence of CD and UC was 201 (95% CI, 197-204) and 238 (95% CI, 234-241), respectively. The prevalence of both conditions was lower in the South, compared with the Northeast, Midwest, and West. IBD appears to be more common in commercially insured individuals, compared with those insured by Medicaid.
  
  
  CONCLUSIONS
  This estimation of the prevalence of IBD in the US should help quantify the overall burden of disease and inform the planning of appropriate clinical services.
authors: Center for Inflammatory Bowel Disease, Division of Gastroenterology and Nutrition, Children's Hospital Boston and Harvard Medical School, Boston, Massachusetts, USA. michael_kappelman@med.unc.edu
authors: Michael D
authors: MD
authors: Kappelman
authors: Sheryl L
authors: SL
authors: Rifas-Shiman
authors: Ken
authors: K
authors: Kleinman
authors: Dan
authors: D
authors: Ollendorf
authors: Athos
authors: A
authors: Bousvaros
authors: Richard J
authors: RJ
authors: Grand
authors: Jonathan A
authors: JA
authors: Finkelstein
mesh_terms: D000293:Adolescent; D000328:Adult; D002648:Child; D002675:Child, Preschool; D003093:Colitis, Ulcerative / Q000453:epidemiology*; D016001:Confidence Intervals; D003424:Crohn Disease / Q000453:epidemiology*; D005260:Female; D006801:Humans; D008297:Male; D016017:Odds Ratio; D015995:Prevalence; D012044:Regression Analysis; D012189:Retrospective Studies; D012307:Risk Factors; D014481:United States / Q000453:epidemiology