Prevalence of Inflammatory Bowel Disease Among Adults Aged ≥18 Years — United States, 2015

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. 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). 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. 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.

Data regarding the health care costs of inflammatory bowel disease (IBD) in the United States are limited. The objectives of this study were to estimate the direct costs of Crohn's disease (CD) and ulcerative colitis (UC) in the United States, describe the distribution of costs among inpatient, outpatient, and pharmaceutical services, and identify sociodemographic factors influencing these costs. We extracted medical and pharmacy claims from an administrative database containing insurance claims from 87 health plans in 33 states, occurring between 2003 and 2004. We identified cases of CD and UC using an administrative definition. For each case, we selected up to 3 non-IBD controls. Claims were classified as inpatient, outpatient, or pharmaceutical according to Current Procedural Terminology codes or National Drug Codes. Costs were based on the paid amount of each claim. IBD-attributable costs were estimated by subtracting costs for non-IBD patients from those for patients with IBD. Logistic regression was used to identify the sociodemographic factors affecting these costs. We identified 9056 patients with CD and 10,364 patients with UC. Mean annual costs for CD and UC were $8265 and $5066, respectively. For CD, 31% of costs were attributable to hospitalization, 33% to outpatient care, and 35% to pharmaceutical claims. The corresponding distribution for UC was 38%, 35%, and 27%, respectively. Costs were significantly higher for children younger than 20 years compared with adults, but this did not vary substantially by sex or region. This study demonstrates a substantial economic burden of IBD and can be used to inform health policy.