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23-11-2011 | Cardiology | Article

Too high, too low sodium increases risk for adverse CV outcomes

Abstract

Free abstract

MedWire News: There is a J-shaped relationship between urinary excretion of sodium and risk for cardiovascular (CV) events, researchers say.

Compared with a baseline sodium excretion of 4.00-5.99 g/day, a sodium excretion of more than 7 g/day is associated with an increased risk for adverse CV events. But a sodium excretion of less than 3 g/day is associated with an increased risk for CV mortality and hospitalization for congestive heart failure (CHF), report Martin O'Donnell (McMaster University, Hamilton, Ontario, Canada) and colleagues.

They investigated the association between estimated urinary sodium and potassium excretion and CV events in 28,880 patients with established CV disease or diabetes mellitus.

The patients involved were from the Ongoing Telmisartan Alone and in Combination with Ramipril Global Endpoint Trial and Telmisartan Randomized Assessment Study in ACE Intolerant Subjects with Cardiovascular Disease study. The researchers used the Kawasaki formula to estimate 24-hour urinary sodium and potassium excretion from the patients' morning fasting urine sample.

The outcomes of interest were CV mortality, myocardial infarction (MI), stroke, and hospitalization for CHF.

Compared with the reference group (n=14,156), which had an estimated baseline sodium excretion of 5.00-5.99 g/day, higher baseline excretion was associated with an increased risk for CV death. Indeed, the risk for CV death almost doubled in patients with baseline excretion of more than 8 g/day, but increased by only 15% in those that had a baseline excretion of 7-8 g/day.

However, a low baseline sodium excretion was associated with an increased risk for the composite of CV death, MI, stroke, and hospitalization for CHF. Patients with a baseline sodium excretion of less than 2 g/day had a 21% increased risk for this outcome, while those with a sodium excretion of 2.00-2.99 g/day had a 16% increased risk.

Compared with an estimated potassium excretion of less than 1.5 g/day (n=2194), higher potassium excretion was associated with a reduced risk for stroke. Indeed, patients with a potassium excretion of 1.50-1.99 g/day had a 23% decreased risk for stroke, while those with an excretion of 2.00-2.49 g/day a 27% reduced risk, those with an excretion of 2.50-3.00 g/day a 29% reduced risk, and those with an excretion of more than 3 g/day a reduced risk of 32%.

However, there was no significant association between sodium and potassium excretion for the composite outcome.

"We found a J-shaped association between estimated sodium excretion and CV events," report the authors in the Journal of the American Medical Association.

They add that the association between high sodium excretion, CV death, and CHF hospitalization "emphasizes the urgent need to establish a safe range for sodium intake in randomized controlled trials."

O'Donnell and team conclude: "Higher urinary potassium excretion was associated with lower stroke risk and is a potential intervention that merits further evaluation for stroke prevention."

Editorialist Paul Whelton (Tulane University School of Public Health and Tropical Medicine, Los Angeles, USA) comments: "The scientific underpinning for the health benefits from sodium reduction is strong, and the available evidence does not support deviating from the stated goal of reducing the exposure to dietary sodium in the general population."

MedWire (www.medwire-news.md) is an independent clinical news service provided by Current Medicine Group, a trading division of Springer Healthcare Limited. © Springer Healthcare Ltd; 2010

By Piriya Mahendra

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