Associations of obesity, sarcopenia, and sarcopenic obesity with the risk of kidney stones in the U.S. Adult: results from NHANES 2011-2018.

Kidney stones (KS), a globally prevalent urological disorder, are linked to metabolic abnormalities and inflammation. Sarcopenia, characterized by progressive skeletal muscle loss and functional decline, frequently coexists with metabolic dysregulation. Sarcopenic obesity (SO), defined by reduced muscle mass and/or function combined with excessive adiposity, may synergistically exacerbate health risks beyond isolated sarcopenia or obesity. However, current studies investigating the relationship between obesity, sarcopenia, SO and KS are limited to single-factor analyses, with limited exploration of inflammatory mediation. This study aims to examine the associations of obesity, sarcopenia, and SO with KS, and for the first time, evaluate the mediating effects of inflammatory biomarkers within these relationships. A total of 10, 043 participants aged ≥ 20 years from the National Health and Nutrition Examination Survey (NHANES) were included. Obesity was defined by body mass index and sarcopenia was assessed using the appendicular muscle index (AMI). SO was defined as the coexistence of sarcopenia and obesity. KS was identified through responses to the "Kidney Conditions-Urology" questionnaire. Weighted multivariable-adjusted logistic regression was used to evaluate the correlation between obesity, sarcopenia, SO and the risk of KS. Mediation models were constructed to assess the mediating role of inflammatory biomarkers. In the U.S. adult population, the prevalence of obesity, sarcopenia, and SO were 35.68%, 7.19%, and 5.27%, respectively. Among the population included in this study, the incidence rates of KS among individuals with obesity, sarcopenia, and SO were 9.77%, 10.92%, and 11.95%, respectively. Multiple regression analysis demonstrated significant independent positive associations between all three body composition disorders and KS incidence after comprehensive adjustment for potential confounding variables. Mediation analyses revealed that neutrophil mediated 11.38% (P = 0.0100), 13.60% (P = 0.0200), and 15.55% (P = 0.0120) of the potential effects of obesity, sarcopenia, and SO on KS formation, respectively. Obesity, sarcopenia, and SO were all positively associated with KS risk in U.S. adults. Neutrophil plays a critical mediating role in the relationship between obesity, sarcopenia, SO and KS.