Abstract
BACKGROUND: Diabetes represents a growing global public health burden. Traditional risk assessments based on static metabolic markers may not adequately reflect underlying mechanisms such as insulin resistance. As the primary site of glucose disposal, skeletal muscle may offer additional insight through functional assessments. However, the predictive value of muscle function indicators, including grip strength and the five-times chair stand test (5-CST), remains uncertain. METHODS: This prospective cohort study comprised 6,604 participants drawn from the China Health and Retirement Longitudinal Study (CHARLS), with follow-up data collected from 2011 to 2020. Muscle strength and physical performance were assessed at baseline using grip strength and 5-CST, respectively. New-onset diabetes was identified through self-report of physician diagnosis. Cox proportional hazards models were used to estimate hazard ratios (HRs) and 95% confidence intervals (CIs) for the association between muscle function indicators and new-onset diabetes, adjusting for potential confounders. Subgroup and interaction analyses were performed by age, gender, and body mass index (BMI). Nomograms and Sankey diagrams were used for data visualization. RESULTS: Among the 6,604 participants, 3,020 were male (45.7%) and 3,584 were female (54.3%), with a median age of 58 years (IQR: 51-65). Low muscle strength was identified in 605 participants (9.2%), and low physical performance in 2,025 (30.7%). Low physical performance was associated with an elevated risk of new-onset diabetes (HR 1.354, 95% CI 1.174-1.561; p < 0.001), which persisted after multivariable adjustment (HR 1.219, 95% CI 1.052-1.414; p = 0.008). This association was stronger in participants aged 40-49 years (HR 1.835, 95% CI 1.249-2.696; p = 0.002), and those with BMI < 25 kg/m² (HR 1.528, 95% CI 1.266-1.845; p < 0.001). Although each 1-second longer 5-CST time was linked to a 2.6% higher risk before adjustment (HR 1.026, p < 0.001), this continuous association was not significant after full adjustment. Neither absolute nor relative grip strength showed independent associations with diabetes risk. CONCLUSIONS: Physical performance surpasses grip strength as a predictor of new-onset diabetes, particularly in middle-aged and non-obese individuals. As a brief, low-resource assessment of lower-limb performance, it provides a practical and scalable tool for identifying high-risk individuals, especially young lean adults who are often missed by traditional risk models.