Recent trends in the epidemiology of IBD in the U.S

Abstract

Objectives: Most U.S. studies of inflammatory bowel disease (IBD) epidemiologyhave sampled small, geographically restricted populations that may not be generalizableto the entire nation and have not examined time trends. This studysought to determine the incidence and prevalence of Crohn's disease (CD) and ulcerativecolitis (UC) in a commercially insured U.S. population and to comparethe prevalence across sociodemographic characteristics and over time. Methods: Using inpatient, outpatient, and pharmaceutical insurance claims datafrom approximately 12 million Americans, we performed 3 consecutive cross-sectionalstudies for the following two-year time periods: 2004-2005, 2006-2007, and 2008-2009. Among those with continuous plan enrollment for each time period, cases of CD and UC were identified using a previously described algorithm basedon diagnosis codes and outpatient pharmaceutical dispensings. Prevalence wasestimated by dividing the number of identified cases by the corresponding numberof individuals in the source population. Cases were assumed to be "incident" if they were continuously enrolled but had no claims for IBD or IBD medicationsin the prior two-year time period. Incidence and prevalence rates were thenstandardized to the age, gender, and regional distribution of the U.S. populationaccording to 2009 census data. Results: The 2009 incidence of CD and UC in individuals younger than 20 years(children) was 12 (95% confidence interval [CI], 10-13) and 7 (95% CI, 7-9) per100, 000, respectively. In individuals 20 years or older (adults), the incidence of CDand UC was 20 (95% CI, 20-21) and 34 (95% CI, 33-35), respectively. The prevalencesof CD and UC in children were 58 (95% CI, 55-60) and 34 (95%CI, 32-36)respectively. In adults, the prevalences were 241 (95% CI, 238-245) and 263(95%CI, 260-266) respectively. Standardized incidence rates for CD and UC havebeen stable in recent years; approximately 8 and 6 respectively among childrenand 21 and 32 respectively among adults. However, the prevalences of both CDand UC have slightly increased. Among children, standardized CD prevalence estimatesrose from 43 to 48 and UC prevalence rose from 27 to 29. Among adults, CD prevalence increased from 214 to 236 and UC prevalence increased from 235to 248. As of 2009, we estimate that approximately 1, 171, 000 Americans have IBD(565, 000 CD and 593, 000 UC). Conclusions: This epidemiological data suggest an increasing prevalence of IBDin recent years, and may be used to inform policy.