Incidence of Frailty, Dementia, and Disability Among Community-Living Older Americans According to County-Level Disadvantage

Background: County-level contextual disadvantage is a novel social determinant of health (SDOH) for older persons. No prior study has evaluated the national incidence of geriatric conditions according to county-level contextual disadvantage among older persons. Our objective was to estimate the incidence of frailty, probable dementia, and disability over a 5-year period on the basis of county-level contextual disadvantage among community-living older Americans. Methods: This prospective, nationally representative longitudinal study used data from the 2015 cohort of the National Health and Aging Trends Study (NHATS), linked to various publicly available, geographically based contextual datasets. County-level disadvantage was assessed using the Geriatric Index of County-Level Multi-Dimensional Contextual Disadvantage (GERi-County), which included nine contextual indicators from these linked datasets. Data on frailty, probable dementia, and activities of daily living (ADL) disability were obtained from the NHATS annual assessments (2015-2020). Results: Totally 7499 participants were included in the analysis, representing 40,728,543 community-living older Americans. The 5-year incidence rates per 1000 person-years were significantly higher in the disadvantaged compared to the non-disadvantaged counties: 52.8 (95% confidence interval (CI), 41.6-64.0) versus 40.3 (95% CI, 37.2-43.3) for frailty; 29.9 (95% CI, 25.4-34.3) versus 21.2 (95% CI, 19.0-23.4) for probable dementia; and 78.1 (95% CI, 70.2-86.0) versus 62.5 (95% CI, 58.2-66.8) for ADL disability. For participants who lived versus did not live in disadvantaged counties, the age- and sex-adjusted HRs were 1.38 (95% CI, 1.08-1.75) for frailty, 1.53 (95% CI, 1.25-1.86) for probable dementia, and 1.30 (95% CI, 1.13-1.49) for ADL disability. Conclusions: Community-living older Americans who reside in disadvantaged counties have a higher incidence of frailty, probable dementia, and ADL disability over a 5-year follow-up period compared to their non-disadvantaged counterparts. Findings underscore the vital, underappreciated role that county-level social contextual disadvantage plays on clinically meaningful outcomes in older persons in the U.S.