Geographic Variation of Prevalence of Alzheimer's Disease and Related Dementias in Central Appalachia.

Background: Alzheimer's disease and related dementias (ADRD) prevalence varies geographically in the United States. Objective: To assess whether the geographic variation of ADRD in Central Appalachia is explained by county-level sociodemographics or access to care. Methods: Centers for Medicare and Medicaid Services Public Use Files from 2015- 2018 were used to estimate county-level ADRD prevalence among all fee-for-service (FFS) beneficiaries with≥1 inpatient, skilled nursing facility, home health agency, hospital outpatient or Carrier claim with a valid ADRD ICD-9/10 code over three-years in Central Appalachia (Kentucky, North Carolina, Ohio, Tennessee, Virginia, and West Virginia). Negative binomial regression was used to estimate prevalence overall, by Appalachian/non-Appalachian designation, and by rural/urban classification. Models were then adjusted for county-level: 1) FFS demographics (age, gender, and Medicaid eligibility), comorbidities; 2) population sociodemographics (race/ethnicity, education, aging population distribution, and renter-occupied housing); and 3) diagnostic access (PCP visits, neurology visits, and imaging scans). Results: Across the 591 counties in the Central Appalachian region, the average prevalence of ADRD from 2015- 2018 was 11.8%. ADRD prevalence was modestly higher for Appalachian counties both overall (PR: 1.03; 95% CI: 1.02, 1.04) and after adjustment (PR: 1.02; 95% CI: 1.00, 1.03) compared to non-Appalachian counties. This difference was similar among rural and urban counties (p = 0.326) but varied by state (p = 0.004). Conclusions: The relative variation in ADRD prevalence in the Appalachian region was smaller than hypothesized. The case mixture of the dual eligible population, accuracy of the outcome measurement, and impact of educational attainment in this region may contribute to this observation.