Sodium Intake, Potassium Intake, Blood Pressure, and Cardiovascular Events

Allan S. Brett, MD

In an observational study of 100,000 people, the associations were complex.

Considerable controversy exists about relations among sodium intake, blood pressure (BP), and adverse cardiovascular events. Researchers explored this issue in an observational study of about 100,000 adults from a mix of 18 high- and low-income countries. Using fasting urinary sodium and potassium measurements, the researchers estimated daily sodium and potassium excretion — a surrogate for intake.

Key BP findings were:

Higher daily sodium excretion was associated with significantly higher systolic and diastolic BP; the association was limited to participants whose daily sodium excretion exceeded 3 g.

• Higher daily potassium excretion was associated with significantly lower systolic BP — an inverse association.
• Mean BP of participants with the highest sodium excretion and lowest potassium excretion was 12/5 mm Hg higher than that of participants with lowest sodium and highest potassium excretion.
• Associations among sodium, potassium, and BP were stronger among hypertensive people than normotensive people.

Key findings for a primary composite outcome (death or major adverse cardiovascular event) during mean follow-up of 3.7 years were:

• Sodium excretion >7 g daily was associated with excess risk for the primary outcome compared with sodium excretion of 4 to 6 g daily (odds ratio, 1.15).
• Sodium excretion <3 g daily also was associated with excess risk for the primary outcome (OR, 1.27); thus, highest and lowest sodium intakes both were associated with adverse clinical outcomes (a “U-shaped” association).
• Adjustment for BP attenuated the association between the primary outcome and high sodium excretion (but not low sodium excretion), suggesting that BP partly mediated the high-sodium finding.
• Low potassium excretion was associated with excess risk for the primary outcome.

Citation(s):

Mente A et al. Association of urinary sodium and potassium excretion with blood pressure. N Engl J Med 2014 Aug 14; 371:601.

O'Donnell M et al. Urinary sodium and potassium excretion, mortality, and cardiovascular events. N Engl J Med 2014 Aug 14; 371:612.