Prognostic Impact of Mild Hypokalemia in Terms of Death and Stroke in the General Population—A Prospective Population Study

Abstract

BackgroundPotassium 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. MethodsParticipants (aged 48-76 years) 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 as potassium <3.4 mmol/L and 3.4-3.6 mmol/L. The primary endpoints were all-cause mortality and nonfatal validated ischemic stroke. The secondary endpoint was acute myocardial infarction (AMI). We adjusted for conventional risk factors, diuretics, and atrial fibrillation at baseline. ResultsMean potassium in the hypokalemic group was 3.5 mmol/L (range, 2.6-3.6 mmol/L) 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 atrial fibrillation 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 (hazard ratio [HR] 1.40; 95% confidence interval [CI], 1.00-1.98). The subgroup with potassium <3.4 mmol/L had higher stroke risk (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. ConclusionIn a general population mild hypokalemia is associated with increased stroke risk and, to a lesser degree, increased mortality risk.