Muscle mass has a greater impact on serum creatinine levels in older males than in females

BACKGROUND AND AIMS: We analyzed the effects of age and sex on the relationship between muscle mass and serum creatinine levels in an apparently healthy population, including older adults. MATERIALS AND METHODS: We retrospectively evaluated 1,502 individuals from the Korea National Health and Nutrition Examination Survey (KNHANES) and 4,586 individuals from the Health Check (HC) groups. We utilized data from the KNHANES and HC groups on serum creatinine levels and skeletal muscle mass index (SMI), determined using dual X-ray absorptiometry or bioelectric impedance analysis. RESULTS: A significant negative correlation between SMI and age was observed in both the KNHANES and HC groups in males but not in females. In males, serum creatinine levels showed a significant negative correlation with age in both the KNHANES (r = −0.522, P < 0.0001) and HC groups (r = −0.451, P < 0.0001). In females, there was no significant correlation between serum creatinine levels and age in the KNHANES (r = −0.016, P = 0.5985) and HC group (r = −0.011, P = 0.5618). CONCLUSIONS: Serum creatinine levels decrease more significantly in older males than in older females due to sex-specific muscle mass decline.