Urinary Sodium-to-Potassium Ratio and Incident Chronic Kidney Disease: Results From the Korean Genome and Epidemiology Study

Abstract

ObjectiveTo evaluate the association of sodium-potassium intake balance on kidney function. Patients and MethodsData from the Korean Genome and Epidemiology Study were used. The participants were enrolled between June 1, 2001, and January 31, 2003, and were followed-up until December 31, 2016. The 24-hour excretion levels of sodium and potassium were calculated using the Kawasaki formula with spot urinary potassium and sodium measurements. Participants were categorized into tertiles according to the estimated 24-hour urinary sodium-to-potassium (Na/K) ratio. The primary outcome was incident chronic kidney disease (CKD), defined as an estimated glomerular filtration rate of <60 mL/min per 1.73 m2 in two or more consecutive measurements during the follow-up period. ResultsThis study included 4088 participants with normal kidney function. The mean age was 52.4±8.9 years, and 1747 (42.7%) were men. The median estimated 24-hour urinary sodium excretion level, potassium excretion level, and Na/K ratio (inter quartile range) were 4.9 (4.1-5.8) g/d, 2.1 (1.8-2.5) g/d, and 2.3 (1.9-2.7) g/d, respectively. During 37,950 person-years of follow-up (median, 11.5 years), 532 participants developed CKD, and the corresponding incidence rate was 14.0 (95% CI, 12.9-15.3) per 1000 person-years. Multivariable Cox hazard analysis revealed that the risk of incident CKD was significantly lower in the lowest tertile than in the highest tertile (HR, 0.78; 95% CI, 0.63-0.97). However, no significant association was found with incident CKD risk when urinary excretion levels of sodium or potassium were evaluated individually. ConclusionA low urinary Na/K ratio may relate with lower CKD development risk in adults with preserved kidney function.