U-Shaped Association of Serum Uric Acid With All-Cause and Cause-Specific Mortality in US Adults: A Cohort Study

Abstract

Abstract Background In addition to the controversy regarding the association of hyperuricemia with mortality, uncertainty also remains regarding the association between low serum uric acid (SUA) and mortality. We aimed to assess the relationship between SUA and all-cause and cause-specific mortality. Methods This cohort study included 9118 US adults from the National Health and Nutrition Examination Survey (1999-2002). Multivariable Cox proportional hazards models were used to evaluate the relationship between SUA and mortality. Our analysis included the use of a generalized additive model and smooth curve fitting (penalized spline method), and 2-piecewise Cox proportional hazards models, to address the nonlinearity between SUA and mortality. Results During a median follow-up of 5.83 years, 448 all-cause deaths occurred, with 100 cardiovascular disease (CVD) deaths, 118 cancer deaths, and 37 respiratory disease deaths. Compared with the reference group, there was an increased risk of all-cause, CVD, cancer, and respiratory disease mortality for participants in the first and third tertiles of SUA. We further found a nonlinear and U-shaped association between SUA and mortality. The inflection point for the curve was found at a SUA level of 5.7 mg/dL. The hazard ratios (95% confidence intervals) for all-cause mortality were 0.80 (0.65-0.97) and 1.24 (1.10-1.40) to the left and right of the inflection point, respectively. This U-shaped association was observed in both sexes; the inflection point for SUA was 6 mg/dL in males and 4 mg/dL in females. Conclusion Both low and high SUA levels were associated with increased all-cause and cause-specific mortality, supporting a U-shaped association between SUA and mortality.