Associations of inflammation/nutrition-related indicators (RAR and MAR) with chronic kidney disease: evidence from NHANES 2005–2018

Objective Ratios of red blood cell distribution width over albumin (RAR) and monocyte count over albumin (MAR) have recently emerged as inflammation- and nutrition-related biomarkers, demonstrating promise has been widely examined for its connection with the manifestation and clinical impact of several diseases. The research seeks to explore a potential link between RAR and MAR and the prevalence of chronic kidney disease (CKD). Methods A cross-sectional analysis was conducted on 27,072 participants from the 2005–2018 NHANES dataset, representative of the U. S. population. Analyses included univariate and multivariate logistic regression, restricted cubic spline modeling, stratified analyses with interaction testing, mediation analyses, and assessment of clinical utility using calibration plots and decision curve analyses. Results The proportion of participants with CKD was found to be 17.7%. After adjusting for a broad set of covariates, logistic regression models with multiple covariates indicated that both RAR and MAR showed significant positive correlations with CKD, with individuals in the highest RAR category exhibiting the strongest associations (OR = 1.68, 95% CI: 1.56–1.80) and highest MAR group (OR = 1.33, 95% CI: 1.24–1.43) had increased odds of CKD. RCS modeling revealed notable nonlinear relationships between RAR and MAR with CKD (nonlinearity test, p < 0.001). Both biomarkers matched observed risks and offered positive net clinical benefit. A significant modification by sex of the link of RAR and CKD prevalence was also detected (interaction p < 0.001). Mediation analyses further indicated that hemoglobin and neutrophil-to-lymphocyte ratio (NLR) partially mediated the associations of RAR and MAR with CKD, respectively. Sensitivity analyses produced consistent outcomes, supporting the robustness of these findings. These findings were further corroborated in an independent hospital-based validation cohort, which showed consistent directions of association of RAR and MAR with CKD. Conclusion Higher levels of the inflammation- and nutrition-related markers RAR and MAR show a link to an increased prevalence of CKD, with these associations partially mediated by hemoglobin and NLR and moderated by sex. Given their simplicity and low cost, RAR and MAR could serve as potential markers for detecting CKD among individuals, although the cross-sectional design precludes causal inference or predictive conclusions.