Design, methods, and rationale in the Hypertension Prevention Trial. Hypertension Prevention Trial Research Group

The Hypertension Prevention Trial (HPT) was a randomized, controlled, multicenter (four clinics, four resource centers) trial designed to test the feasibility of achieving and sustaining dietary changes in the intake of calories, sodium, and potassium and to assess the effect of those changes on blood pressure in a normotensive population. The trial involved 841 men and women (plus a test cohort of 78) who, at the first baseline (BL) examination, were in the age range of 25-49 years and had diastolic blood pressure (DBP) greater than or equal to 76 but less than 100 mm Hg (average of two readings), and at the examination prior to randomization (BL 2) had DBP greater than or equal to 78 but less than 90 mm Hg (also averaged). Participants were randomly assigned to a control treatment group (no dietary counseling) or to one of four dietary treatment groups involving counseling designed to reduce calorie intake, reduce sodium intake, reduce sodium and calorie intake, and reduce sodium and increase potassium intake. Dietary counseling was provided primarily in group settings and was aimed at changing participants' shopping, cooking, and eating habits related to a designated treatment assignment. The effect of dietary counseling was measured through changes in urinary excretion of sodium and potassium, changes in body weight, and changes in reported food intake based on 24-hour food records. Blood pressure changes during the 3-year course of followup were based on measurements taken at 6-month intervals from enrollment using a random-zero sphygmomanometer. This chapter provides a general description of the design and methods of the HPT and the underlying rationale for decisions affecting the design.