High serum uric acid level and low urine pH as predictors of metabolic syndrome: a retrospective cohort study in a Japanese urban population.

The objective of this study was to evaluate whether hyperuricemia, acidic urine, or their combination predicts metabolic syndrome (MetS). In study 1, 69,094 subjects who received a general health checkup between 1985 and 2005 were included in a cross-sectional study of serum uric acid (SUA) and urine pH in relation to MetS. In study 2, the association of SUA and urine pH with MetS development over a 5-year period was evaluated in 5617 subjects with body mass index less than 25 kg/m(2) at the first examination. In study 1, higher SUA and lower urine pH were both positively correlated to MetS status (P < .001). The combination of high SUA and low urine pH was significantly associated with higher MetS prevalence compared with the combination of low SUA and high urine pH (odds ratio, 3.383; 95% confidence interval [CI], 3.034-3.784 in men; odds ratio, 4.000; 95% CI, 2.992-5.452 in women). In study 2, the top quartile of SUA levels was associated with higher MetS development compared with the bottom quartile during the 5-year period in men (hazard ratio [HR], 1.793; 95% CI, 1.084-2.966; P = .023). In women, the HR was 3.732 (95% CI, 0.391-35.62; P = .252) for the upper vs the lower half of SUA levels. For urine pH, the HR was 1.955 (95% CI, 1.089-3.509; P = .025) for the bottom vs the top quartile in men. A likelihood ratio test confirmed that high SUA and low urine pH act synergistically in the development of MetS. High SUA, low urine pH, and their combination are predictive risk factors for MetS development.