Additive interaction between ultrasound-diagnosed metabolic dysfunction-associated steatotic liver disease and hyperuricemia on impaired fasting glucose: a large-scale cross-sectional study

Hyperuricemia and metabolic dysfunction-associated steatotic liver disease (MASLD) independently contribute to dysglycemia, yet their additive interaction on impaired fasting glucose (IFG) remains unquantified. In this cross-sectional study, 17,980 adults undergoing health examinations in Jiaozuo, China (2025) were analyzed. Hyperuricemia was defined by sex-specific thresholds and MASLD by ultrasonography. Participants were cross-classified into four exposure groups. Additive interaction was assessed through relative excess risk due to interaction (RERI), attributable proportion (AP), and synergy index (S) from fully adjusted logistic regression. Restricted cubic splines explored non-linear relationships, and sex-stratified analyses were performed. After full adjustment, the odds of IFG were 2.04 (95% CI 1.70–2.45) for isolated hyperuricemia, 2.85 (95% CI 2.50–3.25) for isolated MASLD, and 4.82 (95% CI 4.10–5.67) for their combination. A positive additive interaction was observed: RERI = 0.93 (95% CI 0.15–1.71; P = 0.019), AP = 0.19 (95% CI 0.05–0.34; P = 0.009), S = 1.34 (95% CI 1.02–1.76; P = 0.035). Spline curves showed a steeper increase in predicted probability beginning around 360 µmol/L in individuals with MASLD, whereas the rise was modest until approximately 420 µmol/L among those without. The interaction estimates appeared larger in women and non-obese participants. Hyperuricemia and MASLD display a positive additive interaction on IFG prevalence. The observed pattern supports considering the combination of elevated uric acid and hepatic steatosis as a marker for intensified glucose surveillance, particularly in women and lean individuals. Prospective studies are needed to evaluate its utility in screening and intervention.