Association between Endothelial Activation and Stress Index (EASIX) and uric acid levels

Elevated serum uric acid is strongly associated with metabolic abnormalities and an increased risk of cardiovascular diseases. Endothelial dysfunction is considered a critical link in metabolic abnormalities. The Endothelial Activation and Stress Index (EASIX), a composite laboratory-based index, has not been systematically examined for its association with serum uric acid levels and endothelial function. This study utilized data from the 2007–2018 National Health and Nutrition Examination Survey (NHANES) with a cross-sectional design to assess the relationship between the EASIX index and serum uric acid levels. Multivariable linear regression analysis was conducted to evaluate their independent association, while restricted cubic splines (RCS) and piecewise regression models were employed to explore nonlinear dose–response trends. Subgroup and sensitivity analyses were performed to validate the robustness of the results. This study included 7602 participants, comprising those with normal and elevated serum uric acid levels. Regression analysis revealed a significant positive correlation between the EASIX index and serum uric acid levels after full adjustment for covariates (β = 0.26, 95% CI: 0.06–0.46). Quartile trend analysis demonstrated that serum uric acid levels increased with rising EASIX. RCS analysis revealed a nonlinear relationship, with serum uric acid levels plateauing at an EASIX value of approximately 1.31, suggesting a “threshold saturation” effect. Subgroup analyses confirmed consistent results across different demographic characteristics and disease statuses, and sensitivity analyses further validated the robustness of the findings. Among US adults, EASIX was positively and nonlinearly associated with serum uric acid levels. Exploratory analysis further suggested that higher EASIX quartiles were associated with increased odds of hyperuricemia. These findings indicate that EASIX may reflect systemic endothelial stress and metabolic burden related to uric acid variation. Further prospective and externally validated studies are needed to determine its clinical utility.