Body roundness index vs. Relative fat mass: associations with cardiovascular-kidney-metabolic syndrome in a cross-sectional study

BACKGROUND: Research has indicated that the primary cause of cardiovascular-kidney-metabolic (CKM) syndrome is excess or dysfunctional adipose tissue. However, traditional anthropometric measures have proven challenging in accurately predicting the likelihood of advanced CKM. The objective of this study was to ascertain the correlation between body roundness index (BRI) and relative fat mass (RFM) and advanced CKM. METHODS: This cross-sectional analysis included data from 12,564 individuals who participated in the National Health and Nutrition Examination Survey (NHANES) between 1999 and 2018. The associations of BRI, RFM and advanced CKM were analyzed using weighted multivariate logistic regression and weighted restricted cubic spline (RCS). Subsequent subgroup analyses were then performed to demonstrate the associations that resulted from the categorization of diverse populations. Furthermore, the capacity of BRI and RFM to distinguish advanced CKM was evaluated using Receiver-operating characteristic (ROC) curves. RESULTS: The advanced CKM group demonstrated higher values for BRI (6.04 ± 0.08 vs. 5.02 ± 0.04) and RFM (35.79 ± 0.26 vs. 34.07 ± 0.13) in comparison to the early CKM group. Following the adjustment of potential confounders in a weighted multivariate logistic model, an independent positive correlation was identified between BRI, RFM, and advanced CKM. The application of restricted cubic splines revealed a positive linear correlation between BRI and advanced CKM (nonlinear p = 0.931), as well as a positive linear relationship between RFM and advanced CKM (nonlinear p = 0.455). Statistically significant effect modifications were observed in the subgroup analyses. The impact of BRI on advanced CKM was found to be modified by both age (P for interaction < 0.05) and smoking status (P for interaction < 0.05). Furthermore, an interaction was identified, suggesting that the association between RFM and advanced CKM was influenced by age, smoking status, and marital status (P for interaction < 0.001). The BRI demonstrated superior discriminatory ability for advanced CKM (AUC 0.63, 95% CI 0.62-0.64) in comparison to all four anthropometric indices in this analysis. CONCLUSIONS: The present study has demonstrated a strong association between BRI and RFM and advanced CKM. BRI has been shown to possess a greater degree of efficacy in differentiating advanced CKM compared to RFM.