Nonlinear Association Between Serum Uric Acid Levels and Mortality in Maintenance Hemodialysis Patients: A Retrospective Study From the Beijing Hemodialysis Quality Control and Improvement Center

BACKGROUND: To investigate the association between serum uric acid levels and the risks of all-cause and cardiovascular mortality in patients undergoing maintenance hemodialysis. METHODS: Patients receiving maintenance hemodialysis registered in 2014 in the Beijing Blood Purification Quality Control and Improvement Center database were included. Patients were stratified into low (≤ 344 μmol/L), intermediate (344-464 μmol/L), and high (> 464 μmol/L) serum uric acid groups. Propensity score matching (1:1:1) was performed using age, sex, diabetes, and dialysis vintage. Survival was analyzed using Kaplan-Meier curves and the log-rank test. Cox proportional hazards models and restricted cubic spline analyses were applied to evaluate the associations between serum uric acid levels and all-cause and cardiovascular death. RESULTS: We enrolled 2070 patients in three matched groups (n = 690 per group). The median follow-up was 64.0 (interquartile range, 31.1-72.0) months. All-cause death occurred in 292/690 (42.3%), 122/690 (17.7%), and 210/690 (30.4%) patients in the low-, intermediate-, and high-serum uric acid groups, respectively. After adjusting for multiple factors, the intermediate serum uric acid group had better survival than the low- (hazard ratio, 1.82; 95% confidence interval [95% CI], 1.41-2.34; p < 0.001) and high-serum uric acid groups (hazard ratio, 2.13; 95% CI, 1.64-2.76; p < 0.001). The pattern of cardiovascular death was consistent with that of all-cause mortality, showing higher risks in both the low- and high-serum uric acid groups compared with the intermediate-serum uric acid group. Further restricted cubic spline analyses suggested a U-shaped association between serum uric acid levels and the risks of all-cause and cardiovascular mortality, with the lowest mortality risk observed at serum uric acid levels of approximately 388-420 μmol/L. CONCLUSION: Serum uric acid exhibited a U-shaped association with the risks of all-cause and cardiovascular death in patients undergoing maintenance hemodialysis. Both excessively low and high serum uric acid levels were associated with increased mortality risk.