The relationship between disability and quality of life among older adults: the roles of sleep, depression, and living arrangements

BACKGROUND: The acceleration of population aging, especially in China, has led to a rapid growth in the number of older adults living with disabilities, posing significant challenges to public health and quality of life (QoL). From the perspective of the biopsychosocial framework, the adverse impact of disability (a biological and functional factor) on QoL has been well documented. However, the underlying mechanisms linking disability to QoL within this framework, especially the mediating roles of psychological factors (e.g., depression) and physiological correlates (e.g., sleep quality), remain insufficiently understood. Furthermore, living arrangements, as a key social factor in the biopsychosocial model, may moderate these mediating pathways. Therefore, this study aimed to examine the mediating roles of sleep quality and depression in the association between disability and QoL and to explore whether living arrangements moderate these pathways within the biopsychosocial framework. METHODS: A total of 3,855 adults aged ≥60 years were recruited through the Household Health Interview Survey in Taian City, China, using a multi-stage stratified cluster sampling method. Data were collected on disability [measured using the Physical Self-Maintenance Scale (PSMS)], sleep quality [assessed using the Pittsburgh Sleep Quality Index (PSQI)], depression [assessed using the Patient Health Questionnaire-9 (PHQ-9)], living arrangements, QoL (assessed using the EQ-5D-5L), and relevant covariates. Statistical analyses included descriptive analysis, logistic regression, and moderated mediation analysis using the PROCESS macro. RESULTS: Disability was significantly associated with poorer QoL (OR = 1.816-1.928, P < 0.001), total effect B = 0.767). Sleep quality and depression partially mediated this association via both parallel and serial pathways, with the serial mediation effect through sleep quality and depression being significant (B = 0.046, P < 0.001). The total indirect effect accounted for 17.00% of the total effect. Furthermore, living arrangements significantly moderated the associations of disability with sleep quality and depression, with stronger adverse effects observed among older adults living alone. CONCLUSION: Disability was associated with poorer QoL among older adults, and this relationship was partially explained by sleep quality and depression, with living arrangements further moderating the pathways linking disability to sleep quality and depression. These findings highlight the importance of integrated interventions that address physical, psychological, and social factors to improve QoL among older adults with disabilities. Targeted strategies, including sleep management, depression screening, and enhanced social support, particularly for those living alone, may help improve QoL and promote healthy aging.