Urinary Potassium Excretion and Progression From Advanced CKD to Kidney Failure

BACKGROUND: Increased dietary potassium intake has well-proven beneficial effects on cardiovascular health and mortality. However, the association between dietary potassium intake and chronic kidney disease (CKD) progression remains unclear with prior studies reporting conflicting results. OBJECTIVE: To study the association between 24-hour urinary potassium excretion (a surrogate for dietary potassium intake) and progression to kidney failure. DESIGN: Retrospective cohort study. SETTING: Ottawa, Canada PATIENTS: Patients with advanced CKD referred to the Ottawa Hospital Multi-Care Kidney Clinic from 2010 to 2020. MEASUREMENTS: Twenty-four-hour urinary potassium excretion measured upon referral to the Ottawa Hospital Multi-Care Kidney Clinic as part of routine clinic protocol. METHODS: Multivariable Cox and Fine and Gray models provided hazard ratios (HRs) and 95% confidence intervals (CIs) to estimate the association between quartiles of 24-hour urinary potassium excretion and progression to kidney failure. A restricted cubic spline analysis examined the possible nonlinear relationship between 24-hour urinary potassium excretion (as a continuous variable) and progression to kidney failure. RESULTS: Overall, 432/695 (62%) patients progressed to kidney failure. Across all models, there was no significant difference in kidney failure risk by quartile of 24-hour urinary potassium excretion (all P values for trend ≥.05). Hazard ratios (95% CIs) from the multivariable-adjusted Cox model were as follows: quartile 1, referent; quartile 2, 0.95 (0.71-1.27); quartile 3, 1.00 (0.76-1.33); and quartile 4 0.85 (0.63-1.14); P value for trend = .36. Restricted cubic spline analysis showed an overall linear and nonsignificant relationship between 24-hour urinary potassium excretion as a continuous variable and progression to kidney failure. LIMITATIONS: Observational design, single center. CONCLUSIONS: We found no association between 24-hour urinary potassium excretion and progression to kidney failure in patients with advanced CKD. Therefore, we identified no clear evidence that increasing or decreasing dietary potassium intake significantly associates with CKD progression in this population. TRIAL REGISTRATION: Not registered.