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. While 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. Research Design and Methods This cross-sectional study included 205 older adults (Mage 80.5 ± 8.1 years; 52.2% male) from six aged care facilities in Taipei. Sarcopenia was assessed using the Asian Working Group for Sarcopenia 2019 criteria. Loneliness was measured via the UCLA Loneliness Scale and perceived fatigability via the validated Traditional Chinese Pittsburgh Fatigability Scale. Causal mediation analysis examined direct and indirect pathways, adjusting for demographic, health, and psychosocial confounders. 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 into institutional settings. Replication in community-dwelling populations is warranted.