April 20, 2007Open Access
Long term effects of dietary sodium reduction on cardiovascular disease outcomes: observational follow-up of the trials of hypertension prevention (TOHP)
Key Result
Dietary sodium reduction in adults with prehypertension reduced the long-term risk of cardiovascular events by 25% (RR 0.75; 95% CI 0.57-0.99; P=0.04) over 10-15 years of follow-up.
Study Design
Type
Observational (n=3,126)
Randomization
Randomized
Multicenter
Yes
Structured PICO
Does dietary sodium reduction reduce cardiovascular disease in adults with prehypertension?
P
Population
3,126 adults aged 30-54 years with prehypertension (diastolic blood pressure 80-89 mm Hg, systolic <140 mm Hg without antihypertensive medication). Includes 744 participants from TOHP I and 2,382 from TOHP II.
I
Intervention
Dietary sodium reduction, including comprehensive education and behavioral counseling on reducing intake, for 18 months (TOHP I) or 36-48 months (TOHP II).
C
Comparator
Usual care control group (followed usual diets and given general guidelines for healthy eating).
O
Outcome
Cardiovascular disease (composite of myocardial infarction, stroke, coronary artery bypass graft, percutaneous transluminal coronary angioplasty, or death with a cardiovascular cause).composite
Main Result
Effect estimate: RR 0.75 (95% CI 0.57-0.99)
p-value: p=0.04
Abstract
OBJECTIVE: To examine the effects of reduction in dietary sodium intake on cardiovascular events using data from two completed randomised trials, TOHP I and TOHP II. DESIGN: Long term follow-up assessed 10-15 years after the original trial. SETTING: 10 clinic sites in 1987-90 (TOHP I) and nine sites in 1990-5 (TOHP II). Central follow-up conducted by post and phone. PARTICIPANTS: Adults aged 30-54 years with prehypertension. INTERVENTION: Dietary sodium reduction, including comprehensive education and counselling on reducing intake, for 18 months (TOHP I) or 36-48 months (TOHP II). MAIN OUTCOME MEASURE: Cardiovascular disease (myocardial infarction, stroke, coronary revascularisation, or cardiovascular death). RESULTS: 744 participants in TOHP I and 2382 in TOHP II were randomised to a sodium reduction intervention or control. Net sodium reductions in the intervention groups were 44 mmol/24 h and 33 mmol/24 h, respectively. Vital status was obtained for all participants and follow-up information on morbidity was obtained from 2415 (77%), with 200 reporting a cardiovascular event. Risk of a cardiovascular event was 25% lower among those in the intervention group (relative risk 0.75, 95% confidence interval 0.57 to 0.99, P=0.04), adjusted for trial, clinic, age, race, and sex, and 30% lower after further adjustment for baseline sodium excretion and weight (0.70, 0.53 to 0.94), with similar results in each trial. In secondary analyses, 67 participants died (0.80, 0.51 to 1.26, P=0.34). CONCLUSION: Sodium reduction, previously shown to lower blood pressure, may also reduce long term risk of cardiovascular events.