Deciphering the association between uric acid and kidney stones: insights into the mediating roles of BMI and serum iron: a cross-sectional study based on NHANES 2007–2018

Background: The relationship between serum uric acid (UA) levels and the prevalence and recurrence of kidney stone (KS) remains unclear. This study aims to investigate the association between UA levels and the risk of KS in a large sample of U.S. adults. Methods: We analyzed the relationship between UA levels and the prevalence of KS among 24 039 U.S. adults from the 2007–2018 National Health and Nutrition Examination Survey. Multivariable logistic regression models were employed to assess the impact of UA on KS prevalence, while restricted cubic splines were used to explore potential nonlinear associations. Mediation analysis was conducted to examine the potential influence of body mass index (BMI) and serum iron on this relationship. Subgroup analyses were also performed to account for demographic differences. Results: Higher serum UA levels were significantly associated with an increased prevalence of KS (OR = 1.001, 95% CI: 1.000–1.002, P < 0.001). This association remained significant after adjustment for covariates such as age, sex, and race, whereas UA levels were not related to KS recurrence. Mediation analysis showed partial effects of serum iron (2.7%) and BMI (20.0%) on the UA-KS relationship. Conclusion: Elevated UA levels are statistically associated with an increased prevalence of KS in U.S. adults but are not linked to recurrence. Serum iron and BMI may partially mediate this relationship. These findings underscore the potential role of UA as a target for KS prevention and offer insights into the underlying biological mechanisms.