Supplementary Material for: Association of remnant cholesterol with rapid kidney function decline in middle-aged and older adults with normal kidney function

Introduction
Emerging evidence suggests a potential association between dyslipidemia and renal dysfunction. Remnant cholesterol, defined as the cholesterol content of triglyceride-rich lipoproteins, has not been thoroughly investigated in relation to rapid renal function decline in individuals with preserved kidney function. Therefore, our study aimed to clarify this association in a nationwide Chinese cohort.
Methods
Our study used data from the 2011 and 2015 waves of the China Health and Retirement Longitudinal Study. Remnant cholesterol level was derived using the following equation: total cholesterol minus low-density lipoprotein cholesterol (LDL-C) and high-density lipoprotein cholesterol. The study outcomes were rapid kidney function decline or the progression to chronic kidney disease (CKD). To determine the associations between remnant cholesterol and CKD outcomes, we used multivariable logistic regression, subgroup analyses, restricted cubic spline models, and receiver operating characteristic curve analysis.
Results
A total of 4039 individuals (59 ± 8.7 years, 52.5% female) were enrolled in our study. Over a 4-year follow-up, 195 (4.8%) individuals experienced rapid renal function decline, and 367(9.1%) individuals experienced progression to CKD. Elevated remnant cholesterol levels were strongly linked to an elevated risk of rapid renal function decline (OR=1.89, 95%CI: 1.59-2.26, P-value < 0.001) and the progression to CKD (OR=1.76, 95%CI: 1.51-2.04, P-value < 0.001). The restricted cubic spline analysis revealed that these associations were nonlinear. Additionally, subgroup analysis demonstrated that this relationship was more evident in individuals with LDL-C ＞ 2.6 mmol/L than those in LDL-C ≤ 2.6 mmol/L.
Conclusion
Our study demonstrated elevated remnant cholesterol concentrations were associated with a higher risk of rapid renal function decline among middle-aged and older Chinese adults. These findings suggest that remnant cholesterol may serve as a valuable biomarker for identifying individuals at elevated risk for renal dysfunction.