Author ORCID Identifier
https://orcid.org/0009-0001-7316-6031
Defense Date
2026
Document Type
Dissertation
Degree Name
Doctor of Philosophy
Department
Rehabilitation and Movement Science
First Advisor
Youngdeok Kim
Abstract
Physical frailty is a prevalent geriatric syndrome characterized by age-related decline across multiple physiological systems. Physical frailty is associated with an elevated risk of adverse health outcomes, including chronic disease progression and all-cause mortality, representing a significant and growing public health concern. Disrupted circadian rest-activity rhythms (RARs) are increasingly recognized as clinically meaningful markers of physical frailty in older adults. However, the extent to which biological sex and social determinants of health (SDoH), particularly social capital, contribute to or modify the associations between RARs and physical frailty remains underexplored.
Therefore, this dissertation summarizes the existing literature on age-related changes in RARs, their association with physical frailty, and possible underlying physiological mechanisms. Then, it further examined the role of biological sex and social capital in the relationships between RAR – characterized using multiple parametric and non-parametric approaches – and physical frailty among older adults.
Consistent with existing literature, population level analyses demonstrated that disrupted RARs, including lower rhythmic strength and greater rhythmic fragmentation, were significantly associated with higher odds of physical frailty, with biological sex emerging as a significant moderator of RAR-frailty associations. In a community-dwelling older adult sample, structural and cognitive dimensions of social capital independently moderate specific RAR-frailty associations. These moderating effects were sex-specific and observed exclusively among older females, suggesting a dynamic role for sex and social capital in shaping the relationship between RAR and physical frailty.
These findings advance a biopsychosocial perspective that links RARs to the risk of physical frailty in later life. Standardized RAR modeling approaches and frailty measurement, together with the systematic integration of SDoH into behavioral epidemiological frameworks, represent important priorities for future research. With such effort, leveraging actigraphy-measured RARs as accessible biobehavioral markers within sex-specific, socially and cognitively informed frailty management strategies may contribute to more equitable and effective approaches to promoting healthy aging in global aging populations.
Rights
© The Author
Is Part Of
VCU University Archives
Is Part Of
VCU Theses and Dissertations
Date of Submission
4-20-2026