Dissertation Defense: Hajin Jang

"Obesity and Muscle Phenotypes as Predictors of Falls in Aging Populations" School of Public Health Department of Epidemiology. Committee: Elsa S. Strotmeyer (chair, advisor), EPIIva Miljkovic, EPISamaneh Farsijani, EPIYing Ding, Biostatistics and Health Data ScienceAbstract Background: Falls are the leading cause of injury and mortality among adults aged 65 years and older in the United States, with 1 in 4 experiencing at least one fall annually. Age-related changes in body composition, characterized by increased adiposity, ectopic fat deposition, and deterioration in muscle quantity and composition, may play a central role in elevated fall risk. However, few studies have examined varied obesity and muscle phenotypes to determine which predict falls in community-dwelling older adults. Objectives: This dissertation examined the associations of (1) whole-body, abdominal, and sarcopenic obesity; (2) D3-creatine (D3Cr) muscle mass and magnetic resonance imaging (MRI)-derived muscle volume and muscle fat infiltration; and (3) computed tomography (CT)-derived fat and muscle area and density, with incident, recurrent, and number of falls in older adults longitudinally. Methods: Participants included: (1) Falls Cross-Cohort Study (FCCS) data, harmonizing the Health, Aging and Body Composition Study (Health ABC), Cardiovascular Health Study (CHS), the Osteoporotic Fractures in Men (MrOS) Study, and Women’s Health Initiative (WHI) (N=15,054, age 75.8 ± 6.2 years); (2) the Study of Muscle, Mobility and Aging (SOMMA) (N=734, age 76.4 ± 5.0 years); and (3) Health ABC (N=2,372, age 73.6 ± 2.9 years), for the three aims. Generalized estimating equations estimated longitudinal odds ratios (ORs) or incidence rate ratios (IRRs) of incident, recurrent, and number of falls, adjusting for demographic, behavioral, and health status-related covariates. Results: In FCCS, whole-body, abdominal, non-sarcopenic obese, sarcopenic non-obese, and sarcopenic obesity were associated with h