Joint and Interactive Associations of the Visceral Adiposity Index and Systemic Inflammatory Markers with Serum Uric Acid Levels among Gas Station Workers

<title>Abstract</title> <p>Objective: To investigate the independent, joint, and interactive associations of the visceral adiposity index (VAI) and systemic inflammatory markers with serum uric acid (SUA) levels among gas station workers in Guangxi, China, and to explore the nonlinear dose-response relationship between VAI and SUA. Methods: This cross-sectional study included 902 gas station workers from a petroleum sales enterprise in Guangxi, China. Demographic characteristics, lifestyle factors, occupational information, anthropometric measurements, and laboratory indicators were collected through questionnaire survey, physical examination, and blood testing. VAI was calculated using waist circumference, body mass index, triglycerides, and high-density lipoprotein cholesterol. Four systemic inflammatory markers were evaluated, including the systemic inflammatory response index (SIRI), neutrophil-to-lymphocyte ratio (NLR), monocyte-to-lymphocyte ratio (MLR), and systemic immune-inflammation index (SII). Multivariable linear regression was used to assess the independent associations of VAI and inflammatory markers with SUA levels. Joint effects were evaluated by cross-classifying VAI and inflammatory markers according to their median values. Multiplicative interactions between VAI and inflammatory markers were examined using interaction terms. Restricted cubic spline analysis was performed to explore the nonlinear association between VAI and SUA. Results: Among the 902 participants, the median SUA level was 331.00 μmol/L (interquartile range: 278.25–397.75), and the prevalence of hyperuricemia was 25.7%. SUA levels and the prevalence of hyperuricemia increased significantly across VAI tertiles (both p &lt; 0.001). After adjustment for age, sex, work seniority, smoking, drinking, physical activity, job category, hypertension, and hyperlipidemia, participants in the middle and highest VAI tertiles had higher SUA levels than those in the lowest tertile, with β values of 20.72 μmol/L (95% CI: 9.56–31.88) and 57.11 μmol/L (95% CI: 45.44–68.78), respectively (p for trend &lt; 0.001). Restricted cubic spline analysis showed a significant nonlinear dose-response relationship between VAI and SUA (p-overall &lt; 0.001, p-nonlinear &lt; 0.001), characterized by a rapid increase in SUA at low-to-moderate VAI levels and a plateau at higher VAI levels. None of the four systemic inflammatory markers showed significant independent associations with SUA levels in the fully adjusted model. Joint effect analysis showed that elevated SUA levels were mainly observed in groups with high VAI, whereas isolated elevation of inflammatory markers contributed little to SUA levels. Significant negative multiplicative interactions were observed between VAI and SIRI, NLR, and SII, with interaction p values of 0.031, 0.003, and 0.022, respectively. No significant interaction was observed between VAI and MLR. Simple slope analysis further indicated that the positive association between VAI and SUA was stronger at lower SIRI levels. Conclusion: Among gas station workers in Guangxi, VAI was positively associated with SUA levels and showed a significant nonlinear dose-response relationship. Systemic inflammatory markers were not independently associated with SUA levels, but SIRI, NLR, and SII modified the association between VAI and SUA. These findings suggest that visceral adiposity may be an important correlate of elevated SUA in this occupational population, while systemic inflammation may act more as an effect modifier than as an independent predictor.</p>