Handgrip strength asymmetry and cardiometabolic multimorbidity in Chinese middle-aged and older adults: a longitudinal cohort study.

BACKGROUND: Handgrip strength asymmetry has been associated with adverse health outcomes, but its longitudinal association with incident cardiometabolic multimorbidity (CMM) remains unclear. We examined this association and conducted exploratory analyses across sleep duration and restless-sleep frequency categories. METHODS: This longitudinal cohort study included 8132 Chinese adults aged 45-80 years without CMM at baseline from the China Health and Retirement Longitudinal Study (2011-2020). Handgrip asymmetry was defined as a ≥ 10% relative difference between hands, and low grip strength was defined according to the Asian Working Group for Sarcopenia 2019 criteria. Participants were categorized as symmetric with normal strength (G1), asymmetric only (G2), weak only (G3), or both asymmetric and weak (G4). Incident CMM was defined as the presence of at least two conditions among diabetes, heart disease, and stroke during follow-up. Cox proportional hazards models, restricted cubic splines, stratified analyses, and sensitivity analysis were performed. RESULTS: During follow-up, 848 participants (10.4%) developed incident CMM. In the fully adjusted model, G2 was associated with a 23% higher risk of incident CMM compared with G1 (HR = 1.23, 95% CI: 1.06-1.42), while G4 was associated with a 67% higher risk (HR = 1.67, 95% CI: 1.27-2.20). G3 was not significantly associated with incident CMM (HR = 1.09, 95% CI: 0.76-1.56). Continuous asymmetry was positively associated with CMM risk, and restricted cubic spline analysis showed a significant overall association but no statistically significant evidence of nonlinearity. No significant multiplicative interactions were observed between handgrip status and restless-sleep frequency or sleep duration (P for interaction = 0.444 and 0.350, respectively), and additive interaction analyses were also non-significant. Sensitivity analyses yielded broadly similar estimates in several alternative models, although the associations for G2 and G4 were attenuated in the analysis restricted to participants without baseline cardiometabolic disease. CONCLUSIONS: Handgrip strength asymmetry was associated with a higher risk of incident CMM, particularly when accompanied by low grip strength. Weakness alone was not significantly associated with CMM in this cohort. Exploratory analyses provided no evidence that sleep duration or restless-sleep frequency significantly modified these associations.