Serum Potassium, Mortality, and Kidney Outcomes in the Atherosclerosis Risk in Communities Study

Abstract

Objectives: To investigate the association between serum potassium, mortality, and kidney outcomes in the general population and whether potassium-altering medications modify these associations.

Patients and methods: We studied 15,539 adults in the Atherosclerosis Risk in Communities Study. Cox proportional hazard regression was used to investigate the association of serum potassium at baseline (1987-1989), evaluated categorically (hypokalemia, <3.5 mmol/L; normokalemia, ≥3.5 and <5.5 mmol/L; hyperkalemia, ≥5.5 mmol/L) and continuously using linear spline terms (knots at 3.5 and 5.5 mmol/L), with mortality, sudden cardiac death, incident chronic kidney disease, and end-stage renal disease. The end date of follow-up for all outcomes was December 31, 2012. We also evaluated whether classes of potassium-altering medications modified the association between serum potassium and adverse outcomes.

Results: Overall, 413 (2.7%) of the participants had hypokalemia and 321 (2.1%) had hyperkalemia. In a fully adjusted model, hyperkalemia was significantly associated with mortality (hazard ratio, 1.24; 95% CI, 1.04-1.49) but not sudden cardiac death, chronic kidney disease, or end-stage renal disease. Hypokalemia as a categorical variable was not associated with any outcome; however, associations of hypokalemia with all-cause mortality and kidney outcomes were observed among those who were not taking potassium-wasting diuretics (all P for interaction, <.001).

Conclusions: Higher values of serum potassium were associated with a higher risk of mortality in the general population. Lower levels of potassium were associated with adverse kidney outcomes and mortality among participants not taking potassium-wasting diuretics.

Figure 1. Cumulative survival by baseline serum potassium concentration^a

^aThere were 5,548 deaths over a median follow-up of 23.5 years. There were 199 deaths among participants with baseline hypokalemia, 5221 deaths among participants with baseline normokalemia, and 128 deaths among participants with baseline hyperkalemia. The cumulative survival was significantly different among three serum potassium groups.

Figure 2. Adjusted hazard ratio of mortality by potassium-wasting diuretics use^a,b

^aReference point (black diamond): The hazard of death among people not taking potassium-wasting diuretics and with baseline serum potassium at 3.5 mmol/L Dots on the line denote that the corresponding hazard ratios are significant different from 1. Shading and error bars correspond to 95% confidence interval for the HR. ^bHR: Hazard ratio