Project Summary African Americans (AA) are at disproportionate risk for earlier and more pronounced cognitive and functional decline and increased frailty. Structural racism (SR)—the systems and processes that create and sustain race- based inequities—is posited as the fundamental driver of accelerated aging and multi-level determinants through its impact on the built and social environment (BSE). We posit that greater and prolonged exposure to historical, enduring, and contemporary (HEC) SR-BSE across the life course promotes greater cognitive and functional declines and increased frailty among AAs. It remains crucial to a) understand the longitudinal relations of cumulative, lifetime exposure to multiple indicators of HEC SR-BSE practices to cognitive aging, functional decline, and emerging frailty; b) delineate variations by race, age, sex and perosn-level socioecnoic status in these linkages; c) evaluate the role of interpersonal discrimination in this context; and d) identify underlying mechanistic pathways of risk (e.g., cardiometabolic disease) and resilience (e.g., social capital). The current project will be the first to thoroughly assess and integrate these goals. Linked to the ongoing Healthy Aging in Neighborhoods of Diversity across the Life Span (HANDLS) epidemiological cohort study, we propose an investigation of up to 800 midlife to older AA and White men and women (ages 30-64 at baseline), tracked up to 13 years across three waves, residing in Baltimore, Maryland. Our sample was born in Baltimore, the U.S. city with the longest history of legalized BSE-based structural racism. This will allow detailed study of cumulative life exposure to the H&C markers we characterize through lifetime residential histories and contemporary activity spaces, obtained by calendar interview and LexisNexis commercial data and linked to rich administrative and archival data from the last 100 years. We will first model potential interactive and independent relations of H&C SR to longitudinal change in cognitive and physical function and frailty with effect modification by race and sex. We will then build structural equation models to address the direct and indirect paths of influence exerted by H&C SR on trajectories of change in these outcomes via neighborhood BSE, interpersonal discrimination, and additional psychological, behavioral, and biomedical factors. We will partner with the Baltimore Neighborhood Indicators Alliance to disseminate our findings to support local, ongoing advocacy and policy work for transformative health equity changes to the BSE, particularly around housing. Understanding and disseminating patterns and mechanistic processes linking H&C SR to accelerated cognitive aging, functional decline, and frailty is critical to the development of appropriate strategies to disrupt racial inequities in accelerated aging via the BSEs where they live.