BMI mediates the association between red cell distribution width to serum albumin index and kidney stone risk: a...

This study aimed to further investigate the relationship between the ratio of red cell distribution width to serum albumin (RAR) index and the risk of kidney stones in the US population, focusing on the mediating effect of body mass index (BMI), and to provide new insights into the prevention and management of kidney stone disease.

This was a cross-sectional study derived from the National Health and Nutrition Examination Survey (NHANES) 2009-2018. The total sample size of the study was 20,755, and the association between RAR and kidney stones was studied using multiple logistic regression, subgroup analysis and mediation analysis.

The findings of this study demonstrate a substantial positive correlation between the prevalence of kidney stones and the RAR index (OR: 1.37, 95% CI: 1.27, 1.49). This association remains consistent even after adjusting for relevant covariates (OR: 1.23, 95% CI: 1.12, 1.36). Utilising curve fitting, threshold effect analysis and restrictive cubic spline methods, an 'S'-shaped non-linear dose-response relationship between the RAR index and the prevalence of kidney stones was identified (p for overall < 0.001, p for non-linear = 0.002). In subgroup analyses, the association between RAR index and the risk of kidney stones was more significant in the obese population (OR: 1.33, 95% CI: 1.18, 1.51, p for interaction = 0.021). The results of the mediation analysis found that BMI played a 24.5% mediating role between the RAR index and kidney stones. Sensitivity analysis also confirmed the stability of this result.

A non-linear association has been identified between the RAR index and the prevalence of kidney stones. The study found that BMI is a mediating variable in this association. In obese individuals of Other Race - Including Multi-Racial, the RAR index has been shown to have a more marked effect on the prevalence of kidney stones.