Association between relative fat mass (RFM) and chronic kidney disease (CKD): data from NHANES 2005-2018

Relative fat mass (RFM) serves as an emerging metric for estimating body fat composition. This study evaluates the association between RFM and chronic kidney disease (CKD) using data from the National Health and Nutrition Examination Survey (NHANES) covering the years 2005-2018. Descriptive statistics were applied to characterize the study population, and logistic regression models assessed the relationships between body mass index (BMI), waist circumference (WC), RFM, and CKD. To further elucidate the RFM-CKD association, subgroup analyses, restricted cubic spline (RCS) modeling, sensitivity analyses, and mediation analyses were conducted. A positive trend was observed, with higher RFM values correlating with increased CKD risk. Compared to the lowest RFM quartile, individuals in the highest quartile exhibited a significantly elevated CKD risk (OR = 1.82; 95% CI 1.46-2.27; p < 0.001). Mediation analysis identified neutrophil-to-lymphocyte ratio, hemoglobin, glycated hemoglobin, and uric acid as significant mediators in this association, with hemoglobin exerting a potentially protective influence. RFM is associated with CKD, suggesting that attention to RFM may be helpful for CKD research.