Neighborhood Environment and Late-Life Cognition: Exploring the Mediating Effect of Sleep and Differential Pathways by Race.

Introduction: Cognition is influenced by the neighborhood social and built environment, but the underlying mechanisms through which neighborhood environments affect cognition are unclear and may differ by race/ethnicity. The authors tested the hypothesis that sleep mediates the association between environmental characteristics and cognition. The authors also explored environment-sleep-cognition interrelationships separately for non-Hispanic White, non-Hispanic Black, and Hispanic older adults in the U.S. Methods: Analyses included older adults from Round 2 of the National Social Life, Health, and Aging Project (N=3,111). The social environment latent variable was constructed using indicators for social cohesion, social ties, and perceived neighborhood danger. The built environment was operationalized using indicators for litter, noise, traffic, pollution, and building conditions. Gross cognitive ability was characterized using the Chicago Cognitive Function Measure as an estimate of Montreal Cognitive Assessment scores. Actigraphic sleep characteristics included sleep fragmentation, time spent awake after sleep onset, and sleep percentage. Results: Participants with better cognition lived in supportive social environments and less hazardous, disruptive (e.g., noisy, polluted) built environments. The sleep mediation hypothesis was partially supported in the full sample: time spent awake after sleep onset mediated the social environment-cognition relationship, but sleep characteristics did not mediate the built environment-cognition relationship. However, in exploratory subgroup analyses, sleep mediated the social environment-cognition relationship among White older adults and mediated the built environment-cognition relationship among Black older adults. Sleep did not mediate any environment-cognition relationships among Hispanic older adults. Conclusions: These results demonstrate that although the social and built environment influence cognition directly and indirectly through sleep, the mediational pathways may vary by specific racial/ethnic subgroups.