J-shaped Association between Serum Uric Acid Levels and the Prevalence of a Reduced Kidney Function: A Cross-sectional Study Using Japanese Health Examination Data.

Objective While an association between a reduced kidney function and hyperuricemia has been reported, its association with hypouricemia is not well understood. The present study therefore investigated this association. Methods Using a large Japanese health examination dataset, we performed a multivariable logistic regression analysis to assess the association between serum uric acid (SUA) levels and a reduced kidney function. The covariates included the age, body mass index, alcohol intake, and the presence of hypertension, dyslipidemia, or diabetes. Patients This study included 227,672 patients (104,854 men; 46.1%), and the analyses were performed separately for men and women. The patients were classified into 5 groups: hypouricemia (SUA ≤2.0 mg/dL) (1st) and four other (2nd-5th) groups with SUA levels of ≤2.0, 2.1-5.1, 5.2-5.9, 6.0-6.8, ≥6.9 mg/dL in men and ≤2.0, 2.1-3.7, 3.8-4.4, 4.5-5.1, ≥5.2 mg/dL in women, respectively. Results The characteristics of the study population were as follows: men, age 55.9±14.9 years old, SUA 5.9±1.3 mg/dL, estimated glomerular filtration rate (eGFR) 80.0±17.2 mL/min/1.73 m, and a reduced kidney function (eGFR <60.0 mL/min/1.73 m) 9.4%; women, age 57.3±15.0 years old, SUA 4.5±1.1 mg/dL, eGFR 81.2±18.0 mL/min/1.73 m, and a reduced kidney function 9.4%. Compared with the 2nd group, the other 4 groups groups had a significantly higher prevalence of a reduced kidney function [odds ratio (OR), 2.58; 95% confidence interval (CI), 1.64-4.06 in men; OR, 1.66; 95% CI, 1.16-2.39 in women]. Conclusion The prevalence of a reduced kidney function was high in both men and women in the hypouricemia and high-SUA groups. SUA levels and the prevalence of a reduced kidney function showed a J-shaped association.