Association between frailty and cognitive function in hospitalized older adults: a moderated serial mediation analysis involving functional status, depression, and social support

Abstract

This study aimed to examine whether impaired basic activities of daily living (BADL) and depression accounted for the association between frailty and cognitive function in hospitalized older adults, and whether social support moderated these relationships. A cross-sectional design was adopted in this study, including hospitalized older adults aged 60 years and above. Data were collected using a digital comprehensive geriatric assessment system, including mini mental state examination (MMSE), frailty scale, BADL scale, geriatric depression scale (GDS), and social support rating scale (SSRS). Hierarchical regression, serial mediation, and moderated mediation analyses were performed using PROCESS macro (Model 92) with 5,000 bootstrap resamples to examine potential statistical pathways from frailty to cognitive function and the moderating role of social support. Among 1,611 hospitalized older adults, frailty was statistically associated with lower MMSE scores. After adjustment for demographic, socioeconomic, and lifestyle-related variables, the direct association was not significant ( p  > 0.05), while the total indirect association was significant, statistically accounting for 88.8% of the observed total association within the specified model. Mediation analysis showed that the indirect association through the pathway of depressive symptoms was the largest, followed by the pathway through BADL and the sequential pathway via BADL and depressive symptoms. In the moderated serial mediation model, social support statistically moderated the link of frailty with BADL ( B  = 0.120, 95% CI 0.056–0.185, p  < 0.001) as well as the link of GDS with MMSE ( B  = 0.014, 95% CI 0.005–0.023, p  = 0.004). Further analysis indicated that as the level of social support increased, the indirect association through the pathways involving depressive symptoms and the sequential pathway gradually decreased. The moderation of social support was statistically significant for the pathways linking frailty with cognitive function through GDS (index = 0.134, 95% CI 0.039–0.227) and through BADL and GDS (index = 0.051, 95% CI 0.025–0.078). The relationship between frailty and cognitive function was mainly characterized by indirect associations involving BADL impairment and depression, with the depression pathway contributing the most statistically. Social support moderated specific associations within this statistical framework. These findings suggest that functional, psychological, and social factors should be considered together in efforts to maintain cognitive health and promote healthy aging among older adults.