Sex, Race, and Age Differences in Prevalence of Dementia in Medicare Claims and Survey Data

This study provides the first comparison of trends in dementia prevalence in the US population using three different dementia ascertainments/data sources: neuropsychological assessment, cognitive tests, and diagnosis codes from Medicare claims.We used data from the nationally representative Health and Retirement Study and Aging, Demographics and Memory Study, and a 20% random sample of Medicare beneficiaries. We compared dementia prevalence across the three sources by race, gender, and age. We estimated trends in dementia prevalence from 2006 to 2013 based on cognitive tests and diagnosis codes utilizing logistic regression.Dementia prevalence among older adults aged 70 and above in 2004 was 16.6% (neuropsychological assessment), 15.8% (cognitive tests), and 12.2% (diagnosis codes). The difference between dementia prevalence based on cognitive tests and diagnosis codes diminished in 2012 (12.4% and 12.9% respectively), driven by decreasing rates of cognitive test-based and increasing diagnosis codes-based dementia prevalence. This difference in dementia prevalence between the two sources by sex and for age groups 75 to 79 and 90 and above vanished over time. However, there remained substantial differences across measures in dementia prevalence among blacks and Hispanics (10.9 and 9.8 percentage points respectively) in 2012.Our results imply that ascertainment of dementia through diagnosis may be improving over time, but gaps across measures among racial/ethnic minorities highlight the need for improved measurement of dementia prevalence in these populations.