The Sodium-Potassium Blood Pressure Trial in Children. Design, recruitment, and randomization: the children and adolescent blood pressure program

Abstract

The Sosium-Potassium Blood Pressure Trial in Children (NaKS), is a clinical trial in a healthy, free living population of children and adolescents. It is designed to test the hypotheses that a reduction in dietary sodium and/or an increase in potassium intake will decrease the rate of rise in blood pressure during normal maturation in children and adolescents with high normal blood pressure. Screening was conducted in 19,452 students in grades 5-8 in Minneapolis and St. Paul between January 1986 and May 1987. After screening, 3,223 students were found to have blood pressures that fulfilled the initial eligibility criteria for the study, and of these, 643 (20.0%) attended the orientation meeting, i.e., the first clinic visit. A total of four clinic visits, designed to test the willingness and capability of the potential participants to comply with the study protocol were conducted prior to randomization. At the conclusion of the four prerandomization visits, 243 children (7.5% of the initially eligible children) agreed to be randomized to one of four trial groups: low-sodium diet; potassium supplement administration; placebo-treated control group; and a no-treatment control group (to test the effect of acclimatization on blood pressure measurements) that will not be seen after randomization until the 4-year termination of the study. The first participant was randomized into the study on June 17, 1986, and the last on December 29, 1987. The potassium and placebo capsules are administered double-masked. Participants will be examined and receive intervention instruction four times yearly for 4 years counted from the date of their randomization. All groups were comparable with regard to distribution of school district, sex, and race and with respect to baseline physical characteristics. Results from this study will provide information about the feasibility and effect of dietary intervention during childhood and adolescence on the prevention of essential hypertension.