By Todd Neale, Senior Staff Writer, MedPage Today
Published: November 22, 2011
Reviewed by Robert Jasmer, MD; Associate Clinical Professor of Medicine, University of California, San Francisco and
Dorothy Caputo, MA, RN, BC-ADM, CDE, Nurse Planner
Action Points
Explain that among patients with increased cardiovascular risk, sodium intake that is too high or too low appears to be associated with an elevated risk of cardiovascular events.
Point out that the increased risk was not elevated on the upper end of intake until sodium levels exceeded 6,500 mg/day, far higher than the upper limits established by the World Health Organization and the American Heart Association.
Among patients with increased cardiovascular risk, sodium intake that is too high or too low appears to be associated with an elevated risk of cardiovascular events, an analysis of two large, randomized controlled trials showed.
The relationship between sodium intake and a composite of cardiovascular death, MI, stroke, and heart failure hospitalization was J-shaped, with elevated risks associated with consumption of more than 8,000 mg and less than 3,000 mg per day, according to Martin O'Donnell, MB, PhD, of McMaster University in Hamilton, Ontario, and colleagues.
The same pattern generally held true for each of the individual components of the outcome as well, the researchers reported in the Nov. 23/30 issue of the Journal of the American Medical Association.
"Our findings emphasize the burden of cardiovascular disease associated with excess sodium intake and the importance of population-based programs to reduce sodium intake in populations consuming high-sodium diets," they wrote.
They noted, however, that risk was not elevated on the upper end of intake until sodium levels exceeded 6,500 mg/day, far higher than the upper limits established by the World Health Organization (2,000 mg/day) and the American Heart Association (1,500 mg/day).
That discrepancy is consistent, however, with the conflicting results of observational studies that have examined the association between sodium intake and cardiovascular events.
The researchers argued for the conduct of large, randomized, controlled trials that would evaluate the effect of reduced sodium intake on cardiovascular outcomes among primary and secondary prevention populations, using a multifactorial dietary intervention.
"Pending the results of such trials, a more cautious approach to policy on sodium intake may be appropriate, one that targets sodium reduction in populations consuming high sodium levels and reflects the uncertainty in those with moderate sodium diets, which includes the majority of the population," they wrote.
The researchers performed an analysis on 28,880 patients from the ONTARGET and TRANSCEND trials. All were 55 or older and had either established cardiovascular disease or high-risk diabetes.
Intake of both sodium and potassium was estimated from baseline urinary samples.
Through a median follow-up of 56 months, cardiovascular death, MI, stroke, or hospitalization for congestive heart failure occurred in 16.4% of the patients.
Compared with patients who had an estimated sodium intake of 4,000 to 5,999 mg/day, those who consumed more than 8,000 mg/day had greater risks of the composite outcome and all of the individual components (HRs 1.48 to 1.66). In addition, an intake of 7,000 to 8,000 mg/day was associated with a 53% greater risk of cardiovascular death.
But lower intake also was associated with poor outcomes.
Compared with the reference group, patients consuming less than 3,000 mg/day had elevated risks of the composite outcome and cardiovascular death (HRs 1.16 to 1.37). An intake of 2,000 to 2,999 mg/day was associated with a greater risk of being admitted for congestive heart failure (HR 1.23).
Potassium intake, a proposed modifier of the relationship between sodium intake and cardiovascular disease, was associated with stroke risk only. Compared with an intake of less than 1,500 mg/day, higher consumption was associated with reduced risks of stroke (HRs 0.68 to 0.77).
In an accompanying editorial, Paul Whelton, MB, MD, of the Tulane University School of Public Health and Tropical Medicine in New Orleans, agreed with the researchers that additional clinical trials designed to determine whether sodium reduction reduces cardiovascular events would be ideal, pointing out the limitations of observational studies.
Still, he said, most U.S. adults consume too much sodium and reducing the addition of sodium to foods "could represent one of the 'lifestyle' changes with the greatest potential for intervention success."
"This shift to a more natural diet would concurrently lead to an absolute increase in dietary potassium content and also lead to an improved sodium-potassium ratio, which may be more desirable than change of either electrolyte on its own," he wrote. "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."
The study was supported by Boehringer Ingelheim.
O'Donnell reported links with Boehringer Ingelheim and other companies manufacturing angiotensin II receptor blockers. Co-authors reported relationships with Boehringer Ingelheim, sanofi-aventis, Abbott Laboratories, Merck, Arena, Vivus, Novo-Nordisk, GlaxoSmithKline, NeuroSearch, Allergan, Johnson & Johnson, Eli Lilly, and Genentech.
Whelton reported that he had no conflicts of interest.
From the American Heart Association:
The Importance of Population-Wide Sodium Reduction as a Means to Prevent Cardiovascular Disease and Stroke
Primary source: Journal of the American Medical Association
Source reference:
O'Donnell M, et al "Urinary sodium and potassium excretion and risk of cardiovascular events" JAMA 2011; 306: 2229-2238.
Additional source: Journal of the American Medical Association
Source reference:
Whelton P "Urinary sodium and cardiovascular disease risk: informing guidelines for sodium consumption" JAMA 2011; 306: 2262-2264.
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