Predictive value of creatinine muscle index reflecting muscle mass for cardiovascular disease among middle-aged and older adults: a cohort study from the CHARLS database

Background The creatinine muscle index (CMI, mg/day/1.73m²) may be a potential indicator for evaluating muscle mass. We aimed to assess the correlation between CMI and muscle mass and investigate the association of CMI with CVD. Methods Participants aged 45–65 years from the 2011 China Health and Retirement Longitudinal Study were included and followed until 2020. CMI was calculated using serum creatinine and cystatin C-estimated glomerular filtration rate. Spearman’s correlation was used to assess the relationship between CMI and appendicular skeletal muscle mass (ASMM). Cox proportional hazards regression models and restricted cubic splines (RCS) were employed to analyze the association between CMI and CVD. Results Among the 5122 participants, 1100 participants developed CVD. CMI was correlated with ASMM in males (r = 0.60, P  < 0.001) and females (r = 0.53, P  < 0.001). After adjusting for multiple factors, higher CMI (tertile 3 versus 1) was associated with reduced risks of CVD in males (HR [95% CI]: 0.74 [0.57–0.95]) and females (HR [95% CI]: 0.79 [0.64–0.97]). RCS revealed a linear relationship between CMI and CVD (all P for non-linearity > 0.05). Conclusions CMI may is a practical indicator of muscle mass, and higher CMI levels are associated with lower CVD risk.