Serum Potassium and Cardiovascular Events

Source: Tufts University
July 16, 2002 (Reviewed: July 16, 2004)

Observational studies have shown an inverse association between dietary potassium intake and risk of cardiovascular disease. However, less is known about the relationship between serum potassium and cardiovascular disease risk. Boston researchers examined Framingham Heart Study data to see if serum potassium levels are predictive of the risk for cardiovascular disease.

Framingham data

The participants were 3,151 men and women enrolled in the Framingham Offspring Study (children of the original cohort members of the Framingham Study) who had serum potassium levels measured between 1979-1983. Individuals with heart disease, serum creatinine concentrations of 2.0 mg/dL or more, extremely high potassium levels (>6.2 mEq/L), or those taking potassium-altering medications were excluded from the study.

Baseline measurements included blood pressure, body mass index (BMI), diabetes diagnosis, smoking status, and alcohol and caffeinated beverage consumption. The main outcomes of interest were cardiovascular disease, death from cardiovascular disease, and death from all causes. Cardiovascular disease included angina pectoris, coronary insufficiency, myocardial infarction, stroke, intermittent claudication, and death due to coronary heart disease or stroke.

No association found

During 16 years of follow-up, 313 cardiovascular events occurred, but serum potassium levels did not predict them. There was no statistically significant association between serum potassium concentration and risk of cardiovascular disease after controlling for blood pressure, hypertension treatment, diabetes, smoking, alcohol and caffeine intake, BMI, and cholesterol levels (Hazards Ratio [HR], 1.00; 95% CI: 0.98 -- 1.03). Similarly, potassium levels had no effect on risk of death from cardiovascular disease or death from all causes (HR, 1.04; 95% CI: 0.97 -- 1.11 and HR, 0.99; 95% CI, 0.96 -- 1.02) after adjusting for confounding factors.

While extremely high or low levels of serum potassium can be lethal and appear to be inversely related to the risk of ventricular arrhythmias, the range commonly seen in a healthy population is not predictive of cardiovascular events, according to this study. This observation differs from the findings of the first National Health and Nutrition Examination Survey Epidemiological Follow-up Survey, which did find an increase in risk of death due to cardiovascular disease in individuals with high serum potassium levels. However, further analysis of the data demonstrated that the increased risk was only in those taking diuretics or with abnormal renal function.

Advice to patients

The authors note that one serum potassium measurement does not account for changes over time; such changes may be predictive of illness. Also, because relatively few people died of cardiovascular disease, the statistical power to detect an association was limited. Further studies are needed to clarify the relationship between serum potassium concentration and death due to cardiovascular disease.

The association between dietary intake of potassium and heart health is clearer, and advice to patients should still be to eat plenty of potassium-rich foods such as orange juice, bananas, spinach, potatoes, and legumes.

Source

• Serum potassium and risk of cardiovascular disease: the Framingham Heart Study. CR. Walsh, MG. Larson, EP. Leip,  et al., Arch Int Med , 2002, vol. 162, pp. 1007--1012

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