The mediating effect of depression on the association between grip strength-to-weight ratio and stroke in middle-aged and older adults: evidence from the China health and retirement longitudinal study

Objective Reduced grip strength-to-weight ratio (GSWR) and depression are both independently associated with increased stroke risk in middle-aged and older adults; Whether depression mediates the relationship between GSWR and stroke remains unclear.Methods We used data from the China Health and Retirement Longitudinal Study (CHARLS), including 8800 individuals aged ≥45 years without a history of stroke. Cox regression, restricted cubic splines (RCS), median, and receiver operating characteristic (ROC) curves were used to evaluate the associations and predictive performance.Results During the follow-up period, stroke occurred in 688 participants. Multivariate Cox regression identified both GSWR and depression as independent risk factors for stroke. Restricted cubic spline analysis demonstrated a significant non-linear association between GSWR and depression (p = 0.002). The combined model with GSWR and depression slightly improves discrimination (AUC = 0.677). Kaplan-Meier analysis revealed the highest stroke incidence among individuals with concurrent low GSWR (<1.052) and high depression scores (≥10) (p < 0.0001). Mediation analysis indicated that depression accounted for 13.42% of the total effect linking GSWR to stroke, whereas GSWR explained 4.18% of the depression-stroke pathway.Conclusion There is only a small improvement in the joint prediction of GSWR and depression. It may enhance stroke risk assessment accuracy in middle-aged and elderly individuals.