The TyG index is negatively associated with sarcopenia in nondiabetic middle-aged and elderly adults based on CHARLS data

Background: This study aimed to investigate the relationship between the TyG index, an alternative marker of insulin resistance, and sarcopenia in nondiabetic middle-aged and elderly people to provide a reference for the prevention and treatment of sarcopenia. Methods: Our study utilized data from the China Health and Retirement Longitudinal Study (CHARLS) 2011-2015 to investigate the prevalence of sarcopenia in nondiabetic middle-aged and elderly adults based on the diagnostic criteria published by the Asian Working Group for Sarcopenia (AWGS) in 2019. Triglyceride and fasting blood glucose values were obtained from physical examination data to calculate the TyG index. The associations between the TyG index and sarcopenia, as well as its components, were analysed using multifactorial logistic regression and restricted cubic spline regression. The relationship between the TyG index and incident sarcopenia was assessed using Cox proportional hazards regression modelling. Results: Of the 7190 subjects included in 2011, 1139 (15.8%) had sarcopenia. There was a significant negative association between the TyG index and sarcopenia in nondiabetic middle-aged and older adults (OR=0.699, 95% CI: 0.588 to 0.830, P <0.001) and a negative association with low muscle mass and low physical function, with adjusted risk ratios of 0.677 and 0.840, respectively.The restricted cubic spline regression analysis showed a nonlinear association, demonstrating a significant negative correlation with sarcopenia when the TyG index was greater than 8.51. During the four-year follow-up, 520 (12.9%) of the 4,034 participants developed sarcopenia. Cox regression analysis revealed that the risk of incident sarcopenia decreased as the TyG index increased (HR=0.631, 95% CI: 0.538-0.741 P <0.001). After adjusting the model based on age, sex, education level, smoking and drinking status, marital status, glycated haemoglobin, high-density lipoprotein, and comorbidities, the trend remained consistent (HR=0.762, 95% CI=0.629-0.923, P =0.005). The adjusted hazard ratio for sarcopenia in the highest quartile of the TyG index compared to the lowest quartile was 0.719 ( P =0.025), indicating a 28.1% reduced risk of new-onset sarcopenia. Conclusions: The TyG index of nondiabetic middle-aged and elderly people in China is negatively correlated with sarcopenia, which may provide a reference for the prevention and management of sarcopenia.