Sleep quality and possible sarcopenia in community-dwelling older adults: physical and mental fatigability as mediators

Assessment of ‘possible sarcopenia’, introduced by the Asian Working Group for Sarcopenia (AWGS) 2019 guidelines, facilitates earlier identification of at-risk individuals. In this study, we examined the association between sleep quality and possible sarcopenia in community-dwelling older adults, and investigated whether physical and mental fatigability mediate this relationship. This cross-sectional study included 200 community-dwelling older adults (mean age 77.52 ± 6.23 years, 48% women) in Taipei, Taiwan. Possible sarcopenia was defined according to AWGS 2019 criteria as low handgrip strength (< 28 kg for men and < 18 kg for women) or poor five-times sit-to-stand test performances (≥ 12 s). Sleep quality was assessed using the Pittsburgh Sleep Quality Index (PSQI; with a score of > 5 indicating poor sleep quality). Physical and mental fatigability were measured using the Pittsburgh Fatigability Scale. After adjusting for age and sex, exploratory mediation analyses examined potential statistical mediation patterns among sleep quality, fatigability dimensions, and possible sarcopenia in these cross-sectional data. Of the 200 participants, 48% (n = 96) met criteria for possible sarcopenia, while 84.5% (n = 169) exhibited poor sleep quality. Participants with poor sleep quality showed a significantly higher prevalence of possible sarcopenia than those with good sleep quality (55.6% vs. 6.5%, p < 0.001). Normal muscle strength was more prevalent among good sleepers (90.3%) compared to poor sleepers (52.1%) (p < 0.001). Participants with possible sarcopenia exhibited significantly higher physical (30.44 ± 7.87 vs. 15.08 ± 5.65, p < 0.001) and mental fatigability scores (27.69 ± 8.78 vs. 12.84 ± 6.29, p < 0.001) with large effect sizes (Cohen’s d ranged 1.53–2.24). A mediation analysis showed statistical associations between poor sleep quality and possible sarcopenia (B = 0.58, standard error (SE) = 0.14, p < 0.001, 95% confidence interval (CI) [0.31, 0.85]). A bootstrap analysis revealed significant indirect effects through physical fatigability (Effect = 0.36, 95% CI [0.20, 0.72]) and mental fatigability (Effect = 0.10, 95% CI [0.01, 0.37]), with physical and mental fatigability accounting for 34.6% and 9.6% of the total statistical effect, respectively. Poor sleep quality showed strong statistical associations with possible sarcopenia among older adults, with physical and mental fatigability showing significant statistical associations. However, the cross-sectional design limited the ability to infer causal relationships among these variables. While these cross-sectional associations cannot establish causation, screening for sleep quality and fatigability may help identify individuals at risk of sarcopenia before significant functional declines occur, though prospective studies are needed to determine whether interventions targeting both factors could serve as components of sarcopenia prevention strategies.