Examining the role of the neighborhood environment on muscle function in older adults

PROJECT SUMMARY/ABSTRACT Poor muscle function is a pressing public health problem: half of all U.S. older adults meet criteria for muscle weakness. Poor muscle function, defined by low muscle strength and power, is a major risk factor for a host of negative health outcomes, including functional limitations, disability and multimorbidity. Neighborhood

characteristics predict functional limitations, disability and death, but the biologic mechanisms are poorly understood. Muscle function and its underlying physiology, including mitochondrial bioenergetics, are a biologically promising, but unexplored mechanism linking neighborhoods and disability. While previous

research has examined neighborhood effects on disability, almost no prior work has explored neighborhood effects on muscle function and no research has evaluated connections with skeletal muscle mitochondria. Neighborhood factors represent an untapped opportunity in musculoskeletal health research directly aligned

with NIA's strategic goals to “assess the interplay among environmental, sociocultural, behavioral, and biological determinants to understand and prevent disease” while “exploring the relationship among mitochondrial biogenesis and musculoskeletal function”. Understanding how neighborhood characteristics get

`under the skin' and contribute to poor muscle function, reduced physical activity, and alter mitochondrial bioenergetics will enhance our understanding of what social and biologic risk factors matter most for muscle function and could be targets for interventions. This study proposal leverages data from two well-characterized datasets, the Health and Retirement Study

(HRS) and the Study of Muscle Mobility and Aging (SOMMA) to identify which features of the neighborhood environment are related to muscle function, physical activity and mitochondrial health in older adults. This proposal seeks to: (1) assess which predictors of the neighborhood environment affect muscle function in older

adults; (2) examine the relationship between the neighborhood environment and skeletal muscle mitochondrial bioenergetics, and; (3) test the hypothesis that mitochondrial bioenergetics and physical activity mediate the link between the neighborhood environment and muscle function. Complementing this research, a detailed training plan, carried out at the University of California, San

Francisco, will build on the applicant's prior training in social and clinical epidemiology to include (1) neighborhood research on planning/design; (2) the assessment of skeletal muscle mitochondrial bioenergetics, and; (3) causal mediation analysis. This integrated sociobiologic training will prepare the applicant for a

successful independent research career focused on incorporating the social determinants of health into the study of musculoskeletal research. Findings from this proposal will provide critical insights into understanding the complex, multifactorial social and biologic contributors of poor muscle function in older adults.