Association of Serum Potassium with All-Cause Mortality in Patients with and without Heart Failure, Chronic Kidney Disease, and/or Diabetes

Abstract

Background: The relationship between serum potassium, mortality, and conditions commonly associated with dyskalemias, such as heart failure (HF), chronic kidney disease (CKD), and/or diabetes mellitus (DM) is largely unknown.

Methods: We reviewed electronic medical record data from a geographically diverse population (n = 911,698) receiving medical care, determined the distribution of serum potassium, and the relationship between an index potassium value and mortality over an 18-month period in those with and without HF, CKD, and/or DM. We examined the association between all-cause mortality and potassium using a cubic spline regression analysis in the total population, a control group, and in HF, CKD, DM, and a combined cohort.

Results: 27.6% had a potassium <4.0 mEq/L, and 5.7% had a value ≥5.0 mEq/L. A U-shaped association was noted between serum potassium and mortality in all groups, with lowest all-cause mortality in controls with potassium values between 4.0 and <5.0 mEq/L. All-cause mortality rates per index potassium between 2.5 and 8.0 mEq/L were consistently greater with HF 22%, CKD 16.6%, and DM 6.6% vs. controls 1.2%, and highest in the combined cohort 29.7%. Higher mortality rates were noted in those aged ≥65 vs. 50-64 years. In an adjusted model, all-cause mortality was significantly elevated for every 0.1 mEq/L change in potassium <4.0 mEq/L and ≥5.0 mEq/L. Diuretics and renin-angiotensin-aldosterone system inhibitors were related to hypokalemia and hyperkalemia respectively.

Conclusion: Mortality risk progressively increased with dyskalemia and was differentially greater in those with HF, CKD, or DM.

Keywords: Chronic kidney disease; Diabetes; Heart failure; Hyperkalemia; Hypokalemia; Mortality.

Fig. 1

Unadjusted mortality (percent) over 18 months and histogram (percent) of serum potassium values per 0.1 mEq/L increments (2.5–8.0 mEq/L) in a: HF, b: CKD, c: DM, and d: combined cohort compared to controls. Data for patients with baseline serum potassium of 8.1–10.0 mEq/L are not reported because the sample size was small (n = 138). CKD, chronic kidney disease; DM, diabetes mellitus, HF, heart failure.

Fig. 2

Spline analysis adjusted for covariates, showing serum potassium as a continuous variable with all-cause mortality over the distribution of potassium values (2.5–8.0 mEq/L) in HF, CKD, DM, and combined cohort compared to controls. Data for patients with baseline serum potassium of 8.1–10.0 mEq/L are not reported because the sample size was small (n = 138). CKD, chronic kidney disease; DM, diabetes mellitus, HF, heart failure.