Changes in urinary Na/K a good indicator of hypertension

Fluctuations in the urinary sodium-to-potassium (Na/K) ratio are linked to changes in systolic (SBP) and diastolic (DBP) blood pressure and to the risk of hypertension, a recent study has found.

The study included 12,890 participants who had undergone check-ups between 2017 and 2018; all participants had available urinary Na/K and BP measurements from both years. Other pertinent information included medications, alcohol consumption, and medical history.

In 2018, the average Na/K ratio was significantly lower than that in 2017 (4.9±2.2 vs 5.4±3.0; p<0.01), as was the average SBP, though only nominally so (130.9±17.4 vs 132.1±17.9 mm Hg). DBP, on the other hand, increased. Body mass index (BMI) and alcohol consumption showed no apparent changes over from 2017 to 2018.

In both 2017 and 2018, the urinary Na/K ratio was significantly and linearly correlated with hypertension, independently of age, sex, BMI, medications, and alcohol consumption.

For instance, in 2017, those with Na/K values 3.0–3.9, the risk of hypertension was only nonsignificantly 3 percent higher than the comparator group with Na/K <3.0 (odds ratio [OR], 1.03, 95 percent confidence interval [CI], 0.90–1.18). Significance was achieved at Na/K 6.0–6.9 (OR, 1.27, 95 percent CI, 1.09–1.48), and in those with Na/K ≥10.0, the risk was more than doubled (OR, 2.16, 95 percent CI, 1.79–2.60). A similar trend was reported in 2018.

Moreover, the change in BP between 2017 and 2018 could be significantly explained by the change in urinary Na/K ratio over the same time span (SBP: β, 0.43; p<0.01; DBP: β, 0.22; p<0.01). Other important explanatory factors were age, sex, and the difference in BMI and alcohol consumption habits between 2017 and 2018.

“The SBP declined at a population level from 2017 to 2018, although the BMI level or proportion of participants who drank alcohol was unchanged. This can be explained partly by a change in urinary Na/K level,” the researchers said.

“Therefore, measuring the urinary Na/K ratio in community settings has the potential to counteract hypertension in a population approach,” they added.