Dietary Sodium to Potassium Ratio and the Incidence of Chronic Kidney Disease in Adults: A Longitudinal Follow-Up Study

The aim of this study was to explore the association of dietary sodium to potassium (Na/K) ratio and the risk of chronic kidney disease (CKD) in general Iranian adults. In this prospective cohort study, 1,780 adults, free of baseline CKD with complete follow-up data, were selected from among participants of the Tehran Lipid and Glucose Study and followed for 6.3 years for development of CKD. Dietary sodium and potassium were assessed using a valid and reliable 168-item food frequency questionnaire. Estimated glomerular filtration rate (eGFR) was calculated using the Modification of Diet in Renal Disease Study equation, and CKD was defined as eGFR <60 mL/min/1.73 m(2). Mean dietary intakes of sodium and potassium were 4,547±3,703 and 3,753±1,485 mg/d, respectively, and their ratio was 1.35±1.29. No significant association was found between dietary intakes of sodium and potassium and the risk of CKD after 6.3 y of follow-up, whereas in the case of dietary Na/K ratio, participants in the highest compared to lowest tertile (2.43 vs 1.61) had a significantly increased risk of CKD (odds ratio=1.52, 95% confidence interval=1.01~2.30); an increasing trend in the risk of CKD across tertiles of dietary sodium to potassium ratio was also observed (P for trend=0.05). Present findings demonstrate that the dietary Na/K ratio is a stronger predictor of CKD than the dietary sodium or potassium per se. Decreased dietary Na/K ratio may be considered as an effective dietary approach to modify the risk of kidney dysfunction.