Association of sarcopenia index, based on serum creatinine and cystatin C, with incident diabetes mellitus

Sarcopenia, characterized by loss of muscle mass and strength, has been linked to various health outcomes, including diabetes mellitus. This study aims to investigate the association of sarcopenia index, based on serum creatinine and cystatin C levels, with incident diabetes mellitus in middle-aged and older adults in China. This study extracted data from 2015 to 2020 China Health and Retirement Longitudinal Study (CHARLS), including age ≥ 45-year adults without diabetes mellitus at baseline. Sarcopenia index was calculated based on serum creatinine and cystatin C levels, and incident diabetes mellitus was assessed through follow-up surveys. Cox proportional hazards regression models were used to analyze the association between sarcopenia index and incident diabetes mellitus, adjusting for potential confounders, with hazard ratio (HR) with 95% confidence interval (95% CI) reported. During a mean follow-up period of 5.0 years, a total of 501 new cases of diabetes were recorded. A total of 7718 participants were included in the analysis. The median age was 60 years, and 46.2% were male. During a mean follow-up period of 5.0 years, 501 cases of incident diabetes mellitus were identified. After adjusting for covariates, Compared with participants in the lowest quartile, the corresponding diabetes HRs (95% CIs) for participants in the second, third, and fourth quartiles were 0.930 (95% CI 0.724-1.193; P = 0.567); 0.892 (95% CI 0.685-1.162; P = 0.398), 0.869 (95% CI 0.657-1.150; P = 0.327). Restricted cubic spline curves revealed that incident rate decreased with increase in sarcopenia index. This study provides national longitudinal evidence in China on the association of sarcopenia index, based on serum creatinine and cystatin C levels, with incident diabetes mellitus in middle-aged and older adults. Our findings suggest that sarcopenia index may be a useful biomarker for predicting the risk of diabetes mellitus in this population.