Inverted U-Shaped Association Between Serum Uric Acid and Handgrip Strength in Chinese Community-Dwelling Adults: A Repeated-Measures Cohort Study

Background: Handgrip strength (HGS) is a robust indicator of muscle strength and overall health, yet its relationship with serum uric acid (SUA) remains unclear due to limitations in linear modeling. This study investigated the nonlinear relationship between SUA and HGS using repeated-measures cohort data. Methods: The cohort consisted of 3016 community-dwelling Chinese adults contributing 4439 repeated measurements (2021–2024). SUA was measured via the uricase–peroxidase method, and HGS was measured via digital dynamometry. Nonlinear associations were evaluated using restricted cubic spline (RCS) linear mixed-effects models and subgroup and sensitivity analyses. Results: No significant linear association was found (p = 0.170). However, RCS analysis revealed an inverted U-shaped curve of the peak HGS at approximately 404 μmol/L SUA (p for nonlinearity < 0.05). When SUA ≤ 404 μmol/L, each standard deviation increase in SUA was associated with a 1.74 kg increase in HGS (p = 0.003), and when SUA > 404 μmol/L, each standard deviation elevation in SUA corresponded to a 0.57 kg decrease in HGS (p = 0.049). This inverted U-shaped relationship was significant in men and participants without type 2 diabetes mellitus (T2DM) but was not observed in women (p for interaction < 0.05) or T2DM patients. Sensitivity analyses confirmed the validity of these results. Conclusions: An inverted U-shaped relationship between SUA and HGS was observed in Chinese adults with an inflection point at approximately 404 μmol/L, modified by sex and notably observed in non-T2DM participants. The results suggest that both low and high SUA levels may impair muscle function, highlighting SUA’s potential as a biomarker for muscle decline and the importance of population-specific management strategies.