The Incidence and Prevalence of Inflammatory Bowel Disease Among Veterans: A National Cohort Study

Abstract

Purpose: The incidence and prevalence of Inflammatory Bowel Disease (IBD) has been reported in primarily Caucasian populations. Users of the Veterans Affairs (VA) health care system are diverse in both age and ethnic distribution. There is increasing recognition of IBD among non-Caucasian patients and the elderly. The incidence and prevalence of IBD among (VA) users are unknown. The aim of this study was to identify the incidence and prevalence of IBD among VA users using the national VA datasets. Methods: We identified veterans with IBD during fiscal years 1998 to 2009 in the national VA administrative datasets, specifically the Patient Treatment Files (PTF) and the Outpatient Care (OPC) files. VA users with ulcerative colitis (UC) and Crohn's disease (CD) were identified by International Classification of Diseases, 9th Revision (ICD-9) diagnosis codes. Prevalent cases of IBD for each fiscal year were identified by presence of any VA encounter during that year in a patient with an ICD-9 code for UC or CD prior to or during that year. Incident cases of IBD for each fiscal year were identified by first appearance of a diagnosis code for UC or CD in subjects with no prior diagnosis code for either UC or CD. Prevalence was calculated based on the total number of VA users in each fiscal year. Incidence was calculated based on the total number of VA users in each fiscal year minus prior prevalent IBD cases. Prevalence and incidence were adjusted for age and gender by direct standardization of the distribution in 1998. Results: The prevalence of both UC and CD are steadily rising among VA users. Age and gender adjusted prevalence of UC increased from 163 per 100,000 VA users in 1998 to 397 per 100,000 in 2009. The adjusted prevalence of CD increased from 112 per 100,000 VA users in 1998 to 285 per 100,000 in 2009. There was no temporal trend in the incidence of UC among VA users between 1998 and 2009, with a range from 27 to 74 per 100,000 per year. Likewise, there was no temporal trend in the incidence of CD among VA users in the same time period, with a range of 22 to 56 per 100,000 per year. Conclusion: Prevalence of both UC and CD are increasing among VA users. As seen in other studies in non-VA populations, there were no consistent temporal trends of incidence of UC or CD among VA users in the past 10 years. This study shows that IBD is prevalent among VA users and the temporal trend of incidence reflects that of the non-VA population.