Prognostic Impact of Mild Hypokalemia in Terms of Death and Stroke in the General Population - a Prospective Population Study

BACKGROUND: Potassium supplementation reduces the risk of cardiovascular mortality and stroke in population studies; however, the prognostic impact of mild hypokalemia in the general population has not been thoroughly investigated. We aimed to investigate associations between mild hypokalemia and endpoints in the general population.

METHODS: participants (48-76 year old) from the general population study "Copenhagen City Heart Study" (n=5916) were studied. Participants were divided into groups according to baseline-values of plasma-potassium (potassium); Hypokalemia (<3.7 mmol/L,n=758), normokalemia (3.7-4.5 mmol/L] n=4973, and high-potassium (>4.5 mmol/L,n=185). Hypokalemia was further divided in potassium<3.4 and 3.4-3.6 mmol/L. The primary endpoints were all-cause mortality and non-fatal validated ischemic stroke. Secondary endpoint was AMI. We adjusted for conventional risk factors, diuretics and atrial fibrillation (AF) at baseline.

RESULTS: Mean potassium in the hypokalemic group was 3.5 mmol/L (range 2.6-3.6) and was associated (P<0.05) with increased systolic blood pressure, higher CHA2DS2-VASc-score, and increased use of diuretics as compared with normokalemia. Baseline AF was equally frequent across groups. Median follow-up-time was 11.9 years (Q1-Q3: 11.4-12.5 years). Hypokalemia was borderline associated with increased stroke-risk in a multivariable Cox model (including adjustment for competing risk) as compared with normokalemia (HR:1.40;95%CI:1.00-1.98). The subgroup with potassium<3.4 mmol/L had higher stroke- (HR:2.10;95%CI:1.19-3.73) and mortality-risk (HR:1.32;95%CI:1.01-1.74) as compared with normokalemia. Hypokalemia was not associated with AMI and no increased risk of mortality was seen with concomitant AMI and hypokalemia. No associations were seen with high-potassium.

CONCLUSIONS: In a general population mild hypokalemia is associated with increased stroke-risk and to a lesser degree increased mortality-risk.