Loneliness and sarcopenia in aged care: the mediating role of fatigability.

Background and Objectives: Sarcopenia prevalence is higher in aged care facilities than in community settings, yet mechanistic pathways remain poorly understood. Although loneliness-sarcopenia associations are established, no studies have examined mediating mechanisms in institutional settings. We examined whether physical and mental fatigability mediate the loneliness-sarcopenia relationship in aged care residents. Methods: This cross-sectional study included 205 older adults ( Results: The sarcopenia prevalence was 58.0%. Physical fatigability significantly mediated the loneliness-sarcopenia association (odds ratio = 1.0, 95% confidence interval: 1.0-1.1), accounting for 15.0% of the total effect. The strongest mediation was for physical performance (44.2%). Substantial interaction effects between loneliness and both physical (74.7%) and mental fatigability (80.5%) suggested synergistic influences on sarcopenia risk. Discussion and Implications: Physical fatigability represents a novel, modifiable mediating pathway between loneliness and sarcopenia in aged care, with particularly strong effects on functional mobility. The substantial interaction effects support the use of combined interventions that address both psychosocial and physiological factors. Dual screening for loneliness and fatigability could identify high-risk residents, addressing the 15.0% mediation pathway. These findings inform integrated care approaches that could transform sarcopenia prevention in institutional settings. Replication in community-dwelling populations is warranted.