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Urinary Sodium and Potassium Excretion, Mortality, and Cardiovascular Events
Study Questions:
What is the optimal range of sodium intake for cardiovascular health?
Methods:
The Prospective Urban Rural Epidemiology (PURE) investigators obtained morning fasting urine samples from 101,945 persons in 17 countries and estimated 24-hour sodium and potassium excretion (used as a surrogate for intake). They examined the association between estimated urinary sodium and potassium excretion, and the composite outcome of death and major cardiovascular events. The authors performed a multivariable logistic regression analysis with generalized estimating equation models (to account for clustering) in order to determine the association between estimated urinary sodium and potassium excretion and death and cardiovascular events, using three sequential models.
Results:
The mean estimated sodium and potassium excretion was 4.93 g per day and 2.12 g per day, respectively. With a mean follow-up of 3.7 years, the composite outcome occurred in 3,317 participants (3.3%). As compared with an estimated sodium excretion of 4.00-5.99 g per day (reference range), a higher estimated sodium excretion (≥7.00 g per day) was associated with an increased risk of the composite outcome (odds ratio, 1.15; 95% confidence interval [CI], 1.02-1.30), as well as increased risks of death and major cardiovascular events considered separately. The association between a high estimated sodium excretion and the composite outcome was strongest among participants with hypertension (p = 0.02 for interaction), with an increased risk at an estimated sodium excretion of ≥6.00 g per day. As compared with the reference range, an estimated sodium excretion that was below 3.00 g per day was also associated with an increased risk of the composite outcome (odds ratio, 1.27; 95% CI, 1.12-1.44). As compared with an estimated potassium excretion that was <1.50 g per day, higher potassium excretion was associated with a reduced risk of the composite outcome.
Conclusions:
The authors concluded that an estimated sodium intake between 3 and 6 g per day was associated with a lower risk of death and cardiovascular events than was either a higher or lower estimated level of intake.
Perspective:
In this large, international, prospective cohort study, the lowest risk of death and cardiovascular events was seen among participants with an estimated sodium excretion between 3 and 6 g per day. Both higher and lower levels of estimated sodium excretion were associated with increased risk, resulting in a J-shaped association curve. The study also found that a higher estimated potassium excretion was associated with a lower risk of the composite of death and major cardiovascular events. Sodium is known to play a critical role in normal human physiology, and activation of the renin–angiotensin–aldosterone system occurs when sodium intake falls below approximately 3.0 g per day, and may potentially explain some of the increased risk with lower sodium intake.
Keywords: Potassium, Sodium, Dietary, Sodium, Renin-Angiotensin System, Blood Pressure, Hypertension, Fasting, Logistic Models
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