High blood pressure is a major risk factor for heart disease and the chief risk factor for stroke. About 65 million American adults, one in three, have high blood pressure. An additional 59 million adults have prehypertension, a level that is above normal, and increases risk of heart disease and stroke. Results of the study, called PREMIER, appear in the April 4, 2006 issue of Annals of Internal Medicine.
“This study underscores the value of lifestyle changes — namely improving diet and increasing physical activity — in reducing high blood pressure, an important public health problem,” said NHLBI Director Elizabeth G. Nabel, M.D. “For the millions of Americans with prehypertension and hypertension, this shows that individuals can make healthy lifestyle changes to keep blood pressure under control without the use of medications.”
A total of 810 men and women ages 25 and older with either prehypertension (120-139mmHg/80-89mmHg) or stage 1 hypertension (140-159mmHg/90-95mmHg) but who were not taking medications to control blood pressure were randomly assigned to three groups. Participants in two of the groups attended 18 counseling sessions during the first six months — 14 group meetings and 4 individual sessions. During the last 12 months they attended 12 group meetings and 3 individual sessions. They were prescribed goals for weight loss, physical activity, and given sodium and alcohol intake limits. One of these groups also received guidance on implementing the Dietary Approaches to Stop Hypertension diet (DASH), an eating plan rich in fruits and vegetables, low-fat dairy products and low in saturated, total fat and dietary cholesterol. DASH is used as an example of a healthy eating plan by the U.S. Dietary Guidelines for Americans, and has been shown to lower blood pressure in previous NHLBI studies.
A third group served as a control, receiving only two 30-minute sessions of advice to follow standard recommendations for blood pressure control; one at study enrollment and one 6 months later. A third session was offered at the end of the 18-month trial after measurements were completed.
The numbers of participants with high blood pressure declined in all three groups, but the reduction was greater in the intervention groups and most striking in the intervention group that included the DASH eating plan. While approximately 37 percent of participants in all three groups had high blood pressure at the study’s start, this was reduced to 22 percent in the group following DASH and 24 percent in the intervention group without DASH. By comparison, the rate of hypertension fell only to 32 percent in the control group.
“Participants in the two intervention groups made greater changes than those in the control group and saw the greatest benefit in blood pressure status,” said Eva Obarzanek, Ph.D., research nutritionist and study co-author. “This shows that people at risk for heart disease can successfully and simultaneously make multiple changes in lifestyle, for a substantial benefit.”
Goals for the intervention groups included a 15 lb weight loss (95 percent of participants were overweight or obese), 3 hours per week of moderate physical activity, daily sodium intakes of no more than 2300 milligrams (1 tsp salt), and limits of one alcoholic drink per day for women, and two per day for men. Those also following the DASH diet were asked to increase their consumption of fruits and vegetables to 9-12 servings per day, consume 2-3 servings of low-fat dairy products, and keep total fat to no more than 25 percent of total daily calories. To keep track, participants kept food diaries, monitored calories and sodium intakes, and recorded minutes of physical activity.
More than one-third of participants had high blood pressure at the beginning of the study. Of these, 62 percent in the intervention group with DASH, and 60 percent in the intervention group without DASH successfully had their blood pressure under control after 18 months (that is, their blood pressure levels were no longer considered high). Comparatively, only 37 percent of the control group with hypertension at the study’s start had their blood pressure under control at the end of the study.
“These rates of hypertension control produced by the two interventions are even better than the 50 percent control rates typically found when single drug therapy is used to control high blood pressure,” said William M. Vollmer, Ph.D., a study investigator from Kaiser Permanente Center for Health Research.
Compared with the control group, one or both intervention groups had:
- Greater weight loss: 5.9 lb in the DASH group and 4.8 lb in the group without DASH.
- Greater improvement in fitness: 2 beats per minute lower heart rate for the DASH group and 1 beat per minute lower heart rate for those without DASH. (The greater the reduction in heart rate, the greater the improvement in fitness.)
- Greater sodium reduction: 354 milligrams for those on the DASH eating plan and 384 milligrams without DASH (about 1/6 tsp less salt).
- Greater reductions in calorie intake: the intervention groups reduced their daily intake by 95 (DASH) and 130 calories (without DASH).
In addition, 25 percent of intervention group participants met the weight loss goal. The group following DASH also achieved increased fruit, vegetable, dairy, fiber and mineral intakes and decreased fat intake.