Estimating the prevalence and economic burden of overactive bladder among Medicare beneficiaries prior to Medicare Part D coverage.

OBJECTIVE: The goal of this study is to provide annual estimates for the treated prevalence and expenditures attributable to overactive bladder (OAB) in the elderly prior to Medicare Part D drug coverage. RESEARCH DESIGN AND METHODS: All Medicare claims were extracted for beneficiaries over 65 with continuous coverage for Medicare Parts A and B during 2003-2004. Two OAB definitions were created: (1) the base case included diagnosis codes that narrowly defined OAB, and (2) the sensitivity variant included additional codes indicative of OAB. Descriptive comparisons of baseline characteristics, annual expenditures, and events and procedures were performed for OAB vs. non-OAB subjects meeting the inclusion criteria. CMS expenditures (2004 US dollars) for individuals were totaled and multiple regression techniques were used to estimate costs attributable to OAB after adjusting for demographic characteristics and comorbid conditions.
RESULTS: The prevalence of subjects with an OAB diagnosis ranged from 8.8 to 13.6% for the base and sensitivity definitions, respectively. While mean total annual expenditures ranged from $9331 to $9655, mean annual expenditures attributable to OAB ranged from $825 to $1184 per subject (9-12% of total medical expenditures for OAB subjects), with aggregate total OAB-attributable expenditures of $1.8-3.9 billion per year.
CONCLUSIONS: The treated prevalence of individuals seeking treatment for OAB in the elderly Medicare population is comparable to some common chronic conditions in that population, and OAB-attributable CMS expenditures are considerable. However, due to study limitations this is a conservative estimate of the direct cost of OAB in the elderly population. The reported estimates exclude pharmacy and out-of-pocket costs, are extrapolated to only two-thirds of the elderly Medicare population, and do not include expenditures by Medicaid for long-term care. Additionally, claims data limits detection of chronic conditions to patients who receive treatment or consultation for OAB; diagnosis codes used were based on expert opinion rather than a review of medical records to identify OAB patients; and long-term care costs are not included.