The association between normalized creatinine-to-cystatin C ratio and incident Circadian Syndrome in middle-aged and older adults: a national cohort study

BACKGROUND: Evidence on the association between the normalized creatinine-to-cystatin C ratio (NCCR) and Circadian Syndrome (CircS) in the general population remains scarce. This study aimed to investigate this relationship using data from middle-aged and elderly participants in the China Health and Retirement Longitudinal Study (CHARLS). METHODS: We conducted a cross-sectional analysis of 5,981 participants (2011 wave) and a prospective cohort analysis of 2,053 participants (2015 wave, median follow-up 4.0 years). CircS was defined as a cluster including elevated blood pressure, dyslipidemia, hyperglycemia, abdominal obesity, depression, and abnormal sleep duration. RESULTS: During follow-up, 552 participants developed incident CircS. A significant inverse association was observed: the risk of new-onset CircS progressively decreased with higher baseline NCCR levels. After adjusting for multiple confounders, each standard deviation increase in NCCR was associated with a 40% reduced odds of CircS (adjusted odds ratio = 0.60, 95% confidence interval: 0.48 to 0.75). Subgroup and dose-response analyses confirmed the robustness of this inverse relationship. CONCLUSIONS: In conclusion, a lower NCCR is independently associated with an elevated risk of developing CircS. These findings support NCCR's role as a practical serum indicator of sarcopenia and implicate muscle loss as a potentially key underlying pathway in the pathogenesis of Circadian Syndrome.