Prospective association of multidimensional dynamic characteristics of relative muscle strength with successful aging in middle-aged and older Chinese adults: a cohort study.

In the context of accelerating population aging globally, successful aging has emerged as a core objective in public health for older adults. Muscle function is a critical protective factor, but prior studies have largely relied on static, single-timepoint measures of grip strength. The prospective associations between the multidimensional dynamic characteristics of relative muscle strength (RMS) and successful aging in middle-aged and older Chinese adults remain unclear. This study aimed to construct a four-dimensional dynamic RMS assessment framework and examine its independent associations with successful aging. Data were from four waves of prospective follow-up in the China Health and Retirement Longitudinal Study (CHARLS) between 2011 and 2018. The final analytical sample included 1,872 middle-aged and older adults. The four-dimensional framework was created using baseline RMS level, cumulative average RMS, longitudinal variability characteristics, and duration of sustained high RMS. Multivariate logistic regression models were used to estimate associations with successful aging. The incidence of successful aging was 7.37% (138/1,872). After full adjustment, baseline RMS (OR = 2.131, 95% CI 1.224-3.669, P = 0.007) and cumulative average RMS (OR = 2.105, 95% CI 1.029-4.304, P = 0.041) were positively associated with successful aging. All longitudinal variability indicators were negatively associated; variability independent of the mean (VIM) showed the strongest association (OR = 0.029, 95% CI 0.003-0.216, P < 0.001). Long-term sustained high RMS (≥ 2 consecutive waves at or above the 75th percentile) was also associated with successful aging (OR = 1.841, 95% CI 1.025-3.229, P = 0.036). Robustness checks supported the main findings. Higher RMS level, lower longitudinal RMS variability, and sustained high RMS over time were each independently associated with successful aging in middle-aged and older Chinese adults. The four-dimensional framework may support health risk stratification and generate hypotheses for future muscle health interventions.