Serum creatinine to cystatin C ratio and risk of incident digestive diseases in middle-aged and older adults: a prospective national cohort study

Evidence regarding the association between the serum creatinine-to-cystatin C ratio (CCR) and digestive disease risk remains limited. This study examined whether CCR is associated with incident digestive diseases among middle-aged and older adults in China. This prospective cohort study included 5,234 participants from the China Health and Retirement Longitudinal Study (CHARLS). CCR was calculated as serum creatinine divided by cystatin C. Incident digestive diseases were identified through self-reports. Multivariable Cox regression models were used to estimate hazard ratios (HRs), and restricted cubic spline analysis was performed to assess the dose-response relationship. Stratified analyses were also conducted. During a mean follow-up of 8.23 ± 2.01 years, 1,131 participants developed digestive diseases (26.25 per 1000 person-years). Each standard deviation increase in CCR was associated with a lower risk of digestive disease (HR = 0.92, 95% CI 0.86-0.98). Compared with the lowest tertile, the middle and highest tertiles showed reduced risks (HR = 0.80, 95% CI 0.70-0.92; HR = 0.78, 95% CI 0.67-0.92). Restricted cubic spline analysis indicated a significant inverse linear association. Lower CCR levels were associated with an increased risk of digestive diseases among middle-aged and older adults. CCR may serve as a simple indicator for early risk assessment, with a preliminary cutoff of < 0.70 identifying high-risk individuals.