The association between sarcopenia and frailty in older adults: a moderated mediation model

The prevalence of sarcopenia and frailty among older adults has emerged as a significant public health concern. Despite the recognition of their impact on health outcomes, the mechanisms linking sarcopenia to frailty remain inadequately explored. This study aimed to investigate the mediating role of functional limitations in the relationship between sarcopenia and frailty, while also examining the moderating effect of handgrip strength in this context. The sample for this study was derived from the 2015 China Health and Retirement Longitudinal Study (CHARLS), which offers nationally representative data. This dataset includes information from 21,097 individuals aged 45 and above, spanning around 150 regions and 450 villages across China. A sample of 2,885 individuals was extracted using RStudio. The outcome variable was frailty, the independent variable was sarcopenia, the mediator was functional limitation, and the moderator was handgrip strength. Spearman correlation analysis was conducted to examine the associations between the primary variables. The mediation and moderation effects were tested using PROCESS version 3.5. In this study, the prevalence of sarcopenia was found to be 15.9% in the elderly population. Grip strength in older adults was negatively correlated with sarcopenia (ρ = − 0.241, P < 0.01), functional limitations (ρ = − 0.245, P < 0.01), and frailty (ρ = − 0.281, P < 0.01). Both sarcopenia (ρ = 0.156, P < 0.01) and functional limitations (ρ = 0.475, P < 0.01) showed positive correlations with frailty. Functional limitations were found to mediate the relationship between sarcopenia and frailty, accounting for 26.23% of the total effect. Additionally, grip strength moderated the initial pathway in the mediation model (β = -0.069, P < 0.05). The functional limitations in older adults mediated the effect of sarcopenia on frailty, and this mediating effect was moderated by handgrip strength.