Pathways explaining racial/ethnic disparities in incident all-cause and Alzheimer's disease dementia among older US men and women.

Abstract

IntroductionRacial disparities in Alzheimer's disease (AD) and all‐cause dementia (DEMENTIA) incidence may exist differentially among men and women, with unknown mechanisms.MethodsA retrospective cohort study examining all‐cause and AD dementia incidence was conducted linking Third National Health and Nutrition Examination Survey (NHANES III) to Centers for Medicare & Medicaid Services Medicare data over ≤26 years of follow‐up (1988 to 2014). Cox regression and generalized structural equation models (GSEMs) were constructed among men and women ≥60 years of age at baseline (N = 4592). Outcomes included onset ages of all‐cause and AD dementia, whereas the main exposures were race/ethnicity contrasts (RACE_ETHN). Potential mediators) included socio‐economic status (SES), lifestyle factors (dietary quality [DIET] nutritional biomarkers [NUTR], physical activity [PA], social support [SS], alcohol [ALCOHOL], poor health [or HEALTH], poor cognitive performance [or COGN]. In addition to RACE_ETHN, the following were exogenous covariates in the GSEM and potential confounders in Cox models: age, sex, urban‐rural, household size, and marital status.ResultsNon‐Hispanic Black (NHB) women had a higher risk of DEMENTIA versus non‐Hispanic White (NHW) women in GSEM, consistent with Cox models (age‐adjusted model: hazard ratio [HR] = 1.34, 95% confidence interval [CI]: 1.10 to 1.61). The total effect of this RACE_ETHN contrast in women was explained by four main pathways: (1) RACE_ETHN→ poor cognitive performance (COGN, +) → DEMENTIA (+); (2) RACE_ETHN → SES (−) → COGN (−) → DEMENTIA (+); (3) RACE_ETHN → SES (−) → physical activity (PA, +) → COGN (−) → DEMENTIA (+); and (4) RACE_ETHN → SES (−) → DIET (+) → COGN (−) → DEMENTIA (+). A reduced AD risk in Mexican American (MA) women versus NHW women upon adjustment for SES and downstream factors (HR = 0.53, 95% CI: 0.35 to 0.80). For the non‐White versus NHW contrast in incident DEMENTIA, pathways involved lower SES, directly increasing cognitive deficits (or indirectly through lifestyle factors), which then directly increases DEMENTIA .DiscussionSocioeconomic and lifestyle factors explaining disparities between NHB and NHW in dementia onset among women are important to consider for future observational and intervention studies.