Serum uric acid, sarcopenia, and muscle strength: A systematic review of dose-response evidence with exploratory meta-analysis.

BACKGROUND: Serum uric acid (SUA) has antioxidant activity but is also linked to metabolic, renal, and inflammatory pathways that may impair skeletal muscle. We assessed whether outcome-specific dose-response evidence identifies a reproducible SUA range associated with better muscle health. METHODS: We reviewed studies reporting three or more SUA categories, category-specific outcomes, or nonlinear models or thresholds. Muscle outcomes were analysed separately by construct and sex. Restricted cubic spline synthesis required at least five independent compatible clusters; small-sample inference used clustered CR2 robust variance. RESULTS: Nineteen reports were retained. Only sex-specific cross-sectional handgrip strength (HGS) supported exploratory nonlinear pooling. Male and female models each comprised five independent clusters, with 13 and 14 non-reference contrasts. Point maxima were 5.92 mg/dL in men (+0.31 kg versus 5.0 mg/dL; 95% CI -2.95 to 3.57; P for nonlinearity = 0.466) and 5.60 mg/dL in women (+0.05 kg; 95% CI -0.78 to 0.87; P for nonlinearity = 0.597). HTZ tests were unreliable (denominator degrees of freedom <0.6), and leave-one-study-out models contained only four clusters. One repeated-measures study reported a 6.79-mg/dL threshold without uncertainty or replicable coefficients. Other outcomes could not be pooled because of sparse, heterogeneous, overlapping, or incomplete data. Certainty was very low for all nine outcome bodies. CONCLUSIONS: Observational evidence does not identify a clinically defensible SUA range that optimizes muscle health. The sex-specific HGS maxima and 6.79-mg/dL threshold are hypothesis-generating, not treatment targets. Prospective sex-specific studies with harmonized outcomes, complete category covariance, and externally validated nonlinear models are needed.