Prevalence of Alzheimer Disease in US States

To the Editors: Alzheimer disease dementia (AD) poses increasing challenges to US states, which dedicate substantial resources to AD care. Chief among these services is long-term nursing home care, a service that many, possibly most, persons with AD require during the course of their illness.1–3 Federal and state governments jointly fund, but individual states manage, Medicaid—the only public health insurance program that provides coverage for this care. However, surveillance systems are not available for gauging the scale of these challenges, and it would be extremely difficult to devise mandatory reporting requirements for AD. Using an alternative approach, we estimated the number of adults, age ≥65 years, with AD in each US state and the District of Columbia (DC) from 2010 to 2025. We computed these estimates by applying the annual AD incidence and AD mortality hazard identified in a large, systematically evaluated community to each state’s population, accounting for each state’s age structure, mortality patterns, and other demographic characteristics. The Supplementary material (eAppendix, https://links.lww.com/EDE/A845) provides extensive detail on these computations, outlined below (as well as presenting further background and sensitivity analyses). We obtained AD incidence and mortality data from the Chicago Health and Aging Project (CHAP),4–6 a longitudinal, population-based study of older adults (60% of whom were black, 40% white). Each 3-year, in-home data-collection cycle included identical clinical evaluations for AD dementia of a stratified, random sample. Between 1997 and 2010, 402 cases of incident AD were identified in 2577 evaluations among 1913 persons who had been classified as free of AD at the previous cycle. Criteria for AD were those of the Work Group of the National Institute of Neurological and Communicative Disorders and Stroke and the Alzheimer’s Disease and Related Disorders Association for probable AD,7 except that persons who met these criteria and had another condition impairing cognition were retained. There were 990 deaths. From these data, we calculated separate annual incidence estimates for 432 groups defined by single year of age (65–100 years); sex, 2 race groups; and 3 education groups. For each state and DC, we applied the incidence estimates computed from CHAP data to the corresponding state subpopulation jointly defined by year of age (beginning with age 65), sex, and calendar year. We then estimated the AD prevalence proportion in each state and DC in each subpopulation jointly defined by year of age, sex, race, and calendar year, incorporating information on the AD and mortality experience of the corresponding birth cohort in previous years. Finally, we multiplied the proportion of prevalent AD by the census estimate of number of people in each age, sex, and race group and summed across groups to obtain total numbers of people with AD. States with larger older adult populations had larger estimated AD prevalences. Between 2010 and 2025, all states, but not DC, are expected to experience double-digit to triple-digit percentage increases in AD prevalence (range, 19% [Pennsylvania] to 116% [Alaska]), with the largest increases occurring in the West and Southeast (Figure 1, e-Table 1, https://links.lww.com/EDE/A845). Some states with the largest predicted percentage increases—California, Florida, and Texas—already have large numbers of adults with the condition. The burden of AD on the AD-free population also will grow: in 2025 older adults with AD are expected to comprise a larger fraction of state populations than they did in 2010 (eTable 2, https://links.lww.com/EDE/A845).FIGURE: Percentage change from 2010 to 2025 in the number of older adults (65 years and older) with AD dementia, by state.Even within age–sex–race–education strata, the experience of the CHAP population might not generalize to state-specific populations or to different points in time. Uncertainty in state population projections contributes additional uncertainty to our estimates. Nonetheless, these limitations are minor compared with the magnitude of the estimated trajectories that portend a substantial increase in the burden of AD on state populations. Jennifer Weuve Liesi E. Hebert Paul A. Scherr Denis A. Evans Rush Institute for Healthy Aging Rush University Medical Center Chicago, IL [email protected]