Does pragmatically structured outpatient dietary counselling reduce sodium intake in hypertensive patients? Study protocol for a randomized controlled trial.

Background: Hypertension is highly prevalent among adults, and is the most important modifiable risk factor for cardiovascular events, in particular stroke. Decreasing sodium intake has the potential to prevent or delay the development of hypertension and improve blood pressure control, independently of blood pressure lowering drugs, among hypertensive patients. Despite guidelines recommending a low sodium diet, especially for hypertensive individuals, sodium intake remains higher than recommended. A recent systematic review indicated that the efficacious counselling methods described in published trials are not suitable for hypertension management by primary care providers in Canada in the present form. The primary reason for the lack of feasibility is that interventions for sodium restriction in these trials was not limited to counselling, but included provision of food, prepared meals, or intensive inpatient training sessions.

Methods/design: This is a parallel, randomized, controlled, open-label trial with blinded endpoints. Inclusion criteria are adult patients with hypertension with high dietary sodium intake (defined as ≥ 100 mmol/day). The control arm will receive usual care, and the intervention arm will receive usual care and an additional structured counselling session by a registered dietitian, with four follow-up telephone support sessions over four weeks. The two primary outcomes are change in sodium intake from baseline, as measured by a change in 24-hour urinary sodium measurements at four weeks and one year. Secondary outcomes include change in blood pressure (as measured by 24-hour ambulatory monitoring), change in 24-hour urinary potassium, and change in body weight at the same time points.

Discussion: Though decreasing sodium intake has been reported to be efficacious in lowering blood pressure, there exists a gap in the evidence for an effective intervention that could be easily translated into clinical practice. If successful, our intervention would be suitable for outpatient programs such as hypertension clinics or interprofessional family practices (family health teams). A negative, or partially negative (positive effect at four weeks with attrition by 12 months) trial outcome also has significant implications for healthcare delivery and use of resources.

Trial Registration: The trial was registered with Clinicaltrials.gov (identifier: NCT02283697) on 2 November 2014.