Urine Potassium Linked to Mortality, but Not Kidney Failure Risk

In patients with chronic kidney disease (CKD), higher urine potassium excretion—as a surrogate for dietary potassium intake—is associated with a lower risk of death but no difference in the risk of kidney failure, reports a study in American Journal of Kidney Diseases.

The study was a post hoc analysis of 812 participants from the Modification of Diet in Renal Disease study. That trial, performed between 1989 and 1993, analyzed the effects of blood pressure control and dietary protein restriction on progression of stage 2 to 4 CKD. The current study analyzed the association of 24-hour urine potassium excretion, measured at baseline and at various times during the study, with the occurrence of kidney failure, defined as dialysis initiation or transplantation. All-cause mortality was also assessed.

At a median follow-up of 6.1 years, kidney failure occurred at a rate of 9 events per 100 patient-years. At a median of 19.2 years, all-cause mortality was 3 deaths per 100 patient-years. The patients’ baseline mean 24-hour urinary potassium excretion was 2.39 g/d.

Urine potassium excretion was unrelated to the risk of kidney failure, but was associated with mortality. For each one-standard deviation increase in baseline urine potassium excretion, there was a 17% decrease in all-cause mortality (hazard ratio 0.83).

In the general population, low urine potassium excretion is associated with increased risks of hypertension and cardiovascular disease. The new study is one of the few to evaluate the association of potassium intake with CKD outcomes.

The results suggest lower all-cause mortality in CKD patients with higher urine potassium excretion, but no significant association with kidney failure risk. “[H]igher potassium intake may provide some benefit even in a population with nondiabetic CKD,” the researchers write. They call for further studies to examine these associations in other groups of kidney disease patients and to explore the underlying mechanisms [Leonberg-Yoo AK, et al. Urine potassium excretion, kidney failure, and mortality in CKD. Am J Kidney Dis 2017; 69:341–349].

April 2017 (Vol 9, Number 4)