Urinary Sodium and Potassium Excretion and the Risk of Cardiovascular Events in CKD

Key Points A high urinary sodium-to-potassium ratio is associated with incident cardiovascular disease in individuals with CKD. Dietary sodium and potassium intake represent potential modifiable risk factors for cardiovascular disease prevention in kidney disease. Further research is needed to determine whether this relationship is causal in nature. Background Kidney disease is a known, independent driver of cardiovascular disease (CVD). While dietary sodium and potassium intake, approximated through urinary excretion, are known cardiac risk factors in the general population, their role for prevention in persons with kidney disease is unclear. Thus, we studied the relationship between the ratio of urinary sodium-to-potassium (Na:K) excretion and incident CVD in individuals with CKD. Methods We included 2342 adults with CKD enrolled in the Chronic Renal Insufficiency Cohort free of CVD on study entry. Urinary sodium and potassium were measured through 24-hour urine collection at the baseline visit. Primary study outcomes included atrial fibrillation (AF), heart failure (HF; overall, HF reduced ejection fraction [HFrEF] and HF preserved ejection fraction), and myocardial infarction (MI). Incidence rates (with 95% confidence intervals [CIs]) were calculated per 1000 person-years. Nested models were created using Cox regression and adjusted for sociodemographic data (age, sex and race/ethnicity), lifestyle habits (body mass index and cigarette smoking), medication use, medical comorbidities, and renal characteristics. Results Among the study population, mean (SD) age was 56 (11) years, and mean eGFR was 51 (20) ml/min per 1.73 m 2 . The highest quartile (versus lowest quartile) of urinary Na:K ratio was associated with a 1.4-fold increased risk of overall HF (hazard ratio [HR], 1.44; 95% CI, 1.05 to 1.98), 1.9-fold increased risk of HFrEF (HR, 1.90; 95% CI, 1.08 to 3.36), and 1.5-fold increased risk of AF (HR, 1.48; 95% CI, 1.03 to 2.13) after adjustment for the covariates above. We did not find an association with incident MI (HR, 1.14; 95% CI, 0.78 to 1.68) and HF preserved ejection fraction (HR, 1.18; 95% CI, 0.75 to 1.87). Conclusions A higher ratio of urinary Na:K excretion was associated with incident AF and HF (particularly HFrEF), but not MI, in persons with CKD. Dietary sodium and potassium represent possible modifiable risk factors for CVD prevention in individuals with kidney disease.