Friday, April 20, 2007

Low salt intake reduces risk of cardiovascular disease

Br Med J 2007; Advance online publication

MedWire News: People could reduce their long-term risk of cardiovascular events by reducing their dietary sodium intake, US researchers say.

"The observed reduction in cardiovascular risk associated with this sodium decrease was substantial and provides strong support for population-wide reduction in dietary sodium intake to prevent cardiovascular disease," the authors write in the British Medical Journal.

Nancy Cook (Harvard Medical School, Boston, Massachusetts) and colleagues followed-up 2415 participants in two randomized trials – the trial of hypertension prevention phase I (TOHP I) and phase II (TOHP II) – for cardiovascular disease and mortality over a period of 10-15 years.

Patients with prehypertension were randomly assigned to an active sodium-reduction intervention or usual care control for 18 months in the TOPH I, and 36-48 months in the TOPH II trial. Net sodium reductions in the intervention groups were 44 and 33 mmol/24 hours, respectively.

The primary outcome was cardiovascular disease, a composite of myocardial infarction, stroke, coronary artery bypass graft, percutaneous transluminal coronary angioplasty, or cardiovascular death.

Patients in the sodium-reduction intervention group had a 25% lower risk of cardiovascular disease compared with those in the control group (relative risk [RR]=0.75, p=0.04), after adjustment for trial, clinic, age, ethnic background, and gender.

Further adjustments for baseline weight and sodium excretion revealed a 30% reduction of cardiovascular disease risk among patients in the sodium intervention group (RR=0.70, p=0.02), compared with controls.

Overall, 35 patients in the sodium group and 42 patients in the control group died, with 10 and 15 of the deaths, respectively, induced by cardiovascular disease. Results were similar for each trial.

Intention to treat analysis showed a mortality risk reduction of 20% among patients in the sodium reduction intervention, compared with those in the control group (RR=0.80, p=0.25).
Cook and co-workers conclude: "People with prehypertension assigned to a sodium reduction intervention experienced a 25-30% lower risk of cardiovascular outcomes in the 10 to 15 years after the trial.

"Sodium reduction, previously shown to lower blood pressure and prevent hypertension, also seems to prevent cardiovascular disease."


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