Supplementary Material for: Elevated Serum Uric Acid Level Predicts Rapid Decline in Kidney Function

Background: While elevated serum uric acid level (SUA) is a recognized risk factor for chronic kidney disease, it remains unclear whether change in SUA is independently associated with change in estimated glomerular filtration rate (eGFR) over time. Accordingly, we examined the longitudinal associations between change in SUA and change in eGFR over 5 years in a general Japanese population. Methods: This was a large, single-center, retrospective 5-year cohort study at St. Luke's International Hospital, Tokyo, Japan, between 2004 and 2009. We included 13,070 subjects (30-85 years) in our analyses whose data were available between 2004 and 2009. Of those, we excluded 492 subjects with eGFR <60 mL/min/1.73 m² at baseline. In addition to examining the entire cohort (n = 12,578), we stratified our analyses by baseline eGFR groups: 60-90, 90-120, and ≥120 mL/min/1.73 m². Linear and logistic regressions models were applied to examine the relationships between baseline and change in SUA, change in eGFR, and rapid eGFR decline (defined as the highest quartile of change in eGFR), adjusted for age, gender, body mass index, abdominal circumference, hypertension, dyslipidemia, and diabetes mellitus. Results: After multivariable adjustments including baseline eGFR, 1 mg/dL increase in baseline SUA was associated with greater odds of developing rapid eGFR decline (OR 1.27, 95% CI 1.17-1.38), and 1 mg/dL increase in SUA over 5 years was associated with 3.77-fold greater odds of rapid eGFR decline (OR 3.77, 95% CI 3.35-4.26). Conclusions: Elevated baseline SUA and increasing SUA over time were independent risk factors for rapid eGFR decline over 5 years.