The study is an observational follow-up of the two Trials of Hypertension Prevention (TOHP I and TOHP II). These studies included 744 and 2,382 patients respectively. Data were collected for 2,415 (77%) of the participants from the combined studies for a primary cardiovascular outcome of consisting of myocardial infarction, stroke, coronary revascularisation or cardiovascular death. The data were analysed to compare patients who had reduced their daily sodium intake (by 44 mmol/24 h in TOHP I and 33 mmol/24 h in TOHP II) to those who received usual care.
The risk of a cardiovascular event was 25% lower (p=0.04) over 10-15 years in the intervention arm after correcting for trial, clinic, age, race and sex. The difference increased to a 30% reduction in risk after additionally correcting for baseline sodium excretion and weight.
All observational studies have inherent limitations and usually the results should be viewed with some caution. However, a large randomised controlled trial investigation the efficacy of reduced sodium intake would be a logistical challenge and is probably not feasible.
Reducing sodium intake is already known to have benefits on blood pressure. A cautious assessment of these results would indicate that reducing sodium intake may be beneficial in preventing cardiovascular events and is unlikely to cause harm.
Action: When providing verbal and written dietary advice, clinicians should incorporate recommendations to reduce dietary sodium intake.