Relative Grip Strength and Incident Disability Among Middle-Aged and Older Chinese Adults: A Prospective Cohort Study from CHARLS

Background Disability poses a significant public health challenge in aging populations. Relative grip strength, defined as handgrip strength standardized by body mass index, is considered a more precise indicator of muscle quality than absolute grip strength. However, its longitudinal association with the risk of disability among middle-aged and older adults in China has not been thoroughly investigated. Methods In this prospective cohort study, we utilized data from the China Health and Retirement Longitudinal Study (CHARLS). We enrolled 10,232 participants aged 45 years or older without disability at baseline in 2011. Relative grip strength was calculated as absolute grip strength divided by body mass index. Disability was defined as needing assistance with at least one of six basic activities of daily living during follow-up. Cox proportional hazards regression models were employed to examine the association between relative grip strength and disability risk, with adjustment for multiple potential confounders. Results During a mean follow-up of 9 years, 3,045 cases of disability were identified, yielding a cumulative incidence of 29.7%. After adjustment for age, sex, lifestyle factors, chronic diseases, and cognitive function, multivariable Cox regression analysis revealed a significant inverse association between relative grip strength and disability risk (HR 0.73, 95% CI 0.66–0.81). When relative grip strength was categorized into quartiles, a significant dose–response relationship was observed (P for trend < 0.001). Participants in the highest quartile (Q4) had a 28% lower risk of disability compared with those in the lowest quartile (Q1) (HR 0.72, 95% CI 0.63–0.83). Restricted cubic spline analysis demonstrated a linear inverse association (P for nonlinearity = 0.442). Subgroup analyses indicated that this association remained consistent across strata defined by age, sex, BMI status, and other characteristics. Conclusion In this middle-aged and older Chinese population, higher relative grip strength is independently associated with a reduced risk of future disability in a dose–response manner. As a simple and practical measure, relative grip strength may serve as a useful indicator for identifying individuals at elevated risk of disability, highlighting its potential value in early screening and preventive public health strategies.