Prevalence of Inflammatory Bowel Disease Far Exceeds Estimates

Approximately three million U.S. adults are estimated to have ever received a diagnosis of inflammatory bowel disease, according to a CDC report published October 28, 2016. This is almost three times the number of adults previously estimated to have inflammatory bowel disease based on less comprehensive data sources.


Crohn’s disease and ulcerative colitis, collectively known as inflammatory bowel disease (IBD), are characterized by chronic inflammation of the gastrointestinal tract. IBD has been associated with poor quality of life and extensive morbidity and often results in complications requiring hospitalizations and surgical procedures. Most previous studies of IBD have used administrative claims data or data collected from limited geographic areas to demonstrate increases in estimated prevalence of IBD within the United States. Few national prevalence estimates of IBD among adults based on large, nationally representative data sources exist, and those that do tend to be based on older data. For example, the most recent national study used 1999 National Health Interview Survey (NHIS) data and estimated that 1.8 million (0.9%) of U.S. adults had IBD. Previous research indicates the burden of IBD to be extensive, including decreased health-related quality of life, high hospitalization rates (8.2–17.1 per 100,000 persons with IBD annually), and direct treatment costs estimated to exceed 6.8 billion dollars in 2008. Understanding the prevalence of IBD in the United States is important to both identify the health and financial burdens created by this disease and to inform policy and resource allocation.


Researchers used data from a nationally representative source to estimate the prevalence of inflammatory bowel disease in the U.S. Specifically, data from the 2015 NHIS were analyzed. The NHIS is a household survey that provides nationally representative estimates on a broad range of health measures for the civilian, noninstitutionalized population. Overall, an estimated 3.1 million, or 1.3%, of U.S. adults have received a diagnosis of IBD. Within population subgroups, a higher prevalence of IBD was identified among adults 45 and older, Hispanics, non-Hispanic whites, and adults with less than a high school level of education, not currently employed, born in the United States, living in poverty, or living in suburban areas. The use of a nationally representative data source such as the NHIS to estimate the prevalence of IBD overall and by population subgroups is important to understand the burden of IBD on the U.S. health care system.


The number of IBD cases and prevalence of IBD (with accompanying 95% confidence intervals) were estimated for the U.S. adult population overall and by various sociodemographic characteristics, including sex, age, race/ethnicity, education level, marital status, current employment status, nativity, health insurance coverage type (reported separately for adults aged under 65 and 65 and older), poverty status (calculated using NHIS imputed income files), urbanicity, and region of residence. Comparisons among subgroups used age-adjusted estimates of IBD prevalence, which were calculated using the projected 2000 U.S. population as the standard population and four age groups: 18 to 24-year-olds, 25 to 44-year-olds, 45 to 64-year-olds, and 65 and older.


Differences in IBD prevalence among a number of sociodemographic subgroups reveal that prevalence is not uniform across the U.S. adult population. Consistent with past research that found the prevalence of both Crohn’s disease and ulcerative colitis increase with age, a higher prevalence of IBD was found among adults 45 and older in this nationally representative population. Furthermore, a significantly higher prevalence of IBD among non-Hispanic whites was found, consistent with racial/ethnic differences previously reported using 1999 NHIS data.


However, other results differed from previous reports. For example, although the current study found no significant differences in the prevalence of IBD by health insurance coverage type among adults aged under age 65 or 65 and older, previous analyses using claims data found that commercially insured persons had a higher prevalence of IBD than did persons insured by Medicaid. Furthermore, significant regional and sex differences identified in past research were not found in this study. Finally, significant differences among sociodemographic characteristics such as education level, employment status, nativity, and poverty status were identified in this study, but not elsewhere. Other researchers have speculated that subgroup differences likely exist for many of the same measures, but small sample sizes and less heterogeneous populations have limited their ability to produce stable, reliable estimates.


Examination of 2015 NHIS data indicates that the prevalence of IBD among adults has increased and far exceeds estimates based on non–nationally representative data sources. Using the NHIS to monitor the prevalence of IBD among U.S. adults can enhance understanding of the health and financial burdens IBD places on the U.S. health care system and help identify subgroups with higher prevalence rates that might be most in need of resources to manage and treat this potentially fatal chronic disease.


See the CDC Report


See also: Medical Law Perspectives December 2016 Report: Gastrointestinal Disorder Liability Risks (to be published December 6, 2016)