Urinary sodium-to-potassium ratio and intake of sodium and potassium among men and women from multiethnic general populations: the INTERSALT Study

The Na/K ratio may be more strongly related to blood pressure and cardiovascular disease than sodium or potassium. The casual urine Na/K ratio can provide prompt on-site feedback, and with repeated measurements, may provide useful individual estimates of the 24-h ratio. The World Health Organization has published guidelines for sodium and potassium intake, but no generally accepted guideline prevails for the Na/K ratio. We used standardized data on 24？h and casual urinary electrolyte excretion obtained from the INTERSALT Study for 10,065 individuals aged 20–59 years from 32 countries (52 populations). Associations between the casual urinary Na/K ratio and the 24-h sodium and potassium excretion of individuals were assessed by correlation and stratification analyses. The mean 24-h sodium and potassium excretions were 156.0？mmol/24？h and 55.2？mmol/24？h, respectively; the mean 24-h urinary Na/K molar ratio was 3.24. Pearson’s correlation coefficients (r) for the casual urinary Na/K ratio with 24-h sodium and potassium excretions were 0.42 and ？0.34, respectively, and these were 0.57 and ？0.48 for the 24-h ratio. The urinary Na/K ratio predicted a 24-h urine Na excretion of <85？mmol/day (the WHO recommended guidelines) with a sensitivity of 99.7% and 94.0%, specificity of 39.5% and 48.0%, and positive predictive value of 96.3% and 61.1% at the cutoff point of 1 in 24？h and casual urine Na/K ratios, respectively. A urinary Na/K molar ratio <1 may be a useful indicator for adherence to the WHO recommended levels of sodium and, to a lesser extent, the potassium intake across different populations; however, cutoff points for Na/K ratio may be tuned for localization