Lung function as a mediator: bridging appendicular skeletal muscle mass and dementia in middle-aged and older Chinese...

The link between appendicular skeletal muscle mass (ASM) and dementia remains unclear. This study investigates whether lung function (LF) mediates the relationship between ASM and dementia in both cross-sectional and longitudinal analyses.

This study utilized data from the China Health and Retirement Longitudinal Study (CHARLS) collected between 2011 and 2018, involving 8,391 participants for cross-sectional and 5,053 for longitudinal analysis. Multivariate logistic regression and Cox proportional hazards models evaluated the links between ASM, LF, and dementia risk. Nonlinear dose-response relationships were assessed with restricted cubic spline (RCS) analysis, and subgroup analyses examined demographic differences. The R package mediation was used for causal mediation analysis, with 95% confidence intervals estimated via a nonparametric bootstrap method (1000 resamples).

In the cross-sectional analysis, logistic regression showed that higher ASM was significantly linked to lower dementia prevalence (OR = 0.94, 95% CI 0.97-0.98, p = 0.009). LF was also strongly and non-linearly associated with lower dementia prevalence (OR = 0.69, 95% CI 0.57-0.85, p < 0.001; nonlinear p < 0.05 from RCS model). LF mediated 14.10% of the ASM-dementia link. In the longitudinal analysis, Cox models found that higher ASM reduced dementia risk (HR = 0.94, 95% CI 0.90-0.98, p = 0.005), as did LF (HR = 0.76, 95% CI 0.62-0.93, p = 0.008). LF accounted for 24.22% of the effect of ASM on dementia incidence.

Higher ASM and better LF are independently linked to lower dementia risk, with LF partially mediating the ASM-dementia association. These results suggest that preserving muscle mass and LF may help prevent dementia in middle-aged and older adults.