Comprehensive lifestyle modification and blood pressure control

At the time of the Prospective Registry Evaluating Myocardial Infarction: Events and Recovery (PREMIER) randomized clinical trial, few studies had examined the effect of multicomponent behavior change interventions on cardiovascular (or any other) outcomes. The PREMIER trial, which was conducted at 4 clinical centers in the United States with funding from the National Heart, Lung, and Blood Institute, tested the effects of 2 combinations of behavior change interventions on blood pressure.^1,2 Both of these interventions encouraged weight loss, increased physical activity, and reduced sodium intake. One also encouraged participants to adopt the Dietary Approaches to Stop Hypertension (DASH) dietary pattern.^3,4 Detailed 6- and 18-month results from the PREMIER study have been previously published.^1,5

Subjects and methods

A total of 810 generally healthy adults with prehypertension or stage 1 hypertension aged 25 years or older were included in the PREMIER study.⁶ Participants were eligible if they had a systolic blood pressure of 120 to 159 mm Hg and a diastolic blood pressure 80 to 95 mm Hg and were not taking antihypertensive medication at the time of enrollment.

Subjects were randomly divided into 3 groups: an advice-only group; a behavioral intervention group that targeted established, guideline-based lifestyle recommendations, including decreased sodium intake, increased physical activity, and weight loss (established); and a behavioral intervention that targeted all of the established recommendations plus the DASH diet (established plus DASH). Subjects in the advice-only group met with a counselor individually at the start of the study and again at the 6-month follow-up visit and were advised to follow the current national recommendations for blood pressure control.⁷ A list of resources and educational materials were provided to these subjects.

A weight loss of 15 pounds or more for subjects with a body mass index (BMI) > 25 kg/m² by exercising 180 minutes per week and a low-fat diet were set as goals for the 2 behavioral intervention groups. Eating 2 to 3 servings of low-fat dairy products per day and 9 to 12 servings of fruits and vegetables per day were also recommended for subjects in the established plus DASH group.

Details of the interventions in the established and established plus DASH groups have been previously published.⁸ In months 1 through 6 of the study, subjects in both groups attended 4 individual counseling sessions and 14 group meetings. They also attended monthly group sessions in months 7 to 18. They were asked to keep records of their physical activity, weight, and food intake.

Physical activity, estimated energy expenditure from physical activity, cardiorespiratory fitness, 24-hour dietary recalls, blood pressure, and weight were recorded at the start of the study and at 6 and 18 months. If subjects had taken antihypertensive drugs in the previous month, blood pressure measurements were censored. For missing and censored 6- and 18-month blood pressure values, we used the blood pressure values for the immediately preceding clinic visits.⁵

Based on national guidelines, if a patient has a continuous systolic blood pressure > 140 mm Hg or a diastolic blood pressure > 90 mm Hg after following a lifestyle modification program for 6 months, he or she should be referred for treatment.^6,7 We therefore expected that a large number of subjects would be placed on medical therapy after the 6-month visit, necessitating censoring their blood pressure data in the 18-month analysis. The trial's primary outcome was therefore blood pressure change at 6 months. For the 18-month visit, the primary outcome was hypertension status, defined as blood pressure > 140/90 mm Hg and/or taking medication to control high blood pressure. Changes in lifestyle variables, changes in systolic blood pressure and diastolic blood pressure, and hypertension control were additional outcomes assessed.

Results

At baseline, the mean blood pressure (systolic/diastolic) was 134.9/84.8 mm Hg for the cohort as a whole, 143.9/87.5 mm Hg for those who initially had hypertension, and 129.5/83.2 mm Hg for prehypertensive subjects. There were no significant differences in baseline characteristics among the 3 groups. The mean age of subjects was 50 years, 38% were men, and 34% were African American. A total of 95% were overweight (BMI > 25 kg/m²) or obese (BMI > 30 kg/m²), and 38% had hypertension.

Attendance at intervention sessions and follow-up data collection visits was high. Ninety-four percent of subjects had at least 1 blood pressure measurement at 18 months. The mean number of subjects who attended the 2 active intervention groups was 24 and 25 of the possible 33 intervention visits over 18 months.

Although all 3 groups exhibited a mean weight loss from baseline to 18 months, the reductions were much greater in the intervention groups than in the advice-only group (P < .001; Table 1). The weight loss goal of 15 pounds was reached by about 25% of subjects in the 2 intervention groups. Although not statistically significant, participants in the 2 behavioral intervention groups reported more physical activity and had better objectively measured fitness than did participants in the advice-only group at 18 months. Both intervention groups exhibited significant reductions in sodium and total caloric intake at 18 months, compared with the advice-only group.

Table 1. Weight, fitness, physical activity, sodium intake, and total caloric intake by randomized

group. Click on table image for larger version.

Consistent with its added emphasis on the DASH diet, subjects in the established plus DASH group significantly increased their daily intake of fruits and vegetables, dairy products, and carbohydrates while decreasing their intake of total and saturated fat, compared with the other 2 groups (Table 2). Although the magnitude of these differences was diminished from its peak at 6 months, it remained significant through 18 months.

Table 2. Markers of DASH dietary intake from 24-hour recalls by randomized group. Click on table image for larger version.

For the 3 groups, the prevalence of hypertension was 36% to 38% at baseline. At the 18-month follow-up visit, hypertension had decreased to 32% for the advice-only group, 24% for the established group (P = .10 vs advice-only group), and 22% for the established plus DASH group (P = .023 vs advice-only group; Table 3). For those subjects who had hypertension at the start of the study, the prevalence of hypertension at 18 months was 63% for the advice-only group, 40% for the established group (P = .003 vs advice-only group), and 38% for the established plus DASH group (P = .001 vs advice-only group).

Table 3. Prevalence of hypertension, prevalence of normal blood pressure, proportion

using antihypertensive medications, and systolic and diastolic blood pressure at baseline,

6 months, and 18 months by randomized group. Click on table image for larger version.

The prevalence of hypertension did not differ significantly between the established and established plus DASH groups.

In terms of secondary outcomes, none of the subjects had optimal blood pressure, defined as systolic blood pressure < 120 mm Hg and diastolic blood pressure < 80 mm Hg at baseline without the use of antihypertensive medication.⁶ At 18 months, however, 18% of the advice-only, 24% of the established, and 24% of established plus DASH subjects had normal blood pressures (P > .05 for each pairwise contrast). Despite the fact that the mean reductions in blood pressure were greater for the established and established plus DASH groups than for the advice-only group, these differences were not statistically significant.

Discussion

The findings from our study show that lifestyle changes can be achieved and continued over 18 months and can lead to improved hypertension control. Subjects in the behavioral intervention groups reduced their weight and decreased their consumption of fat and sodium. Those in the established plus DASH group also decreased their intake of total fat and saturated fat while increasing their intake of fruits, vegetables, and dairy products.

Importantly, the established plus DASH intervention included the Seventh Report of the Joint National Committee on Prevention, Detection, Evaluation, and Treatment of High Blood Pressure dietary recommendations for controlling blood pressure.⁷ Thus, the extent to which these participants made and sustained lifestyle changes is of particular interest. Although the greatest lifestyle changes were seen at 6 months, much of this change was maintained at 18 months, especially increases in fruit, vegetable, and dairy consumption and decreases in saturated fat intake.

Both behavioral intervention groups showed mean weight losses of 5% to 6% from baseline weight during the first 6 months. Much of the weight loss was maintained at 18 months, with mean decreases of about 4% from baseline weight.⁵ This level of weight loss is significant in light of the public health objectives stressing prevention of further weight gain rather than weight loss, and the loss shown in our study occurred despite the well documented difficulties in maintaining weight loss.^9,10

Our findings contradict concerns that patients cannot make several lifestyle changes at the same time.^11,12 Contemporary behavioral methods, including frequent feedback, reinforcement, self-monitoring, and problem solving, are probably responsible for the success of the subjects in the intervention groups.

The chief blood pressure—related outcome was hypertension at 18 months. In the subjects who were hypertensive at baseline, the achievement of hypertension control at 18 months in the established plus DASH group (62%) was both clinically and statistically better than in the advice-only group (37%). Results from this trial are in agreement with community data that suggest that drug therapy controls blood pressure in about half of hypertensive patients.¹³

The effects of intervention were attenuated between the 6- and 18-month visits, partly because of the sustained intervention effects in the advice-only group. It is possible that the frequent follow-up measurement schedule had an unintended placebo effect in the advice-only group.

Conclusions

Compared with the advice-only group, subjects in the established and established plus DASH groups lost weight and decreased their fat and sodium intake. The PREMIER trial showed that subjects with prehypertension and stage 1 hypertension were able to make long-term lifestyle changes that reduced their risk of cardiovascular disease. Because the prevalence of hypertension has been shown to be significantly increasing in the United States,¹⁴ interventions, such as the ones implemented in the PREMIER study, are critically important.

AcknowledgmentsThe authors wish to acknowledge the editorial assistance of Ms Martha Swain in the preparation of this manuscript. The PREMIER study was supported by National Heart, Lung, and Blood Institute grants UO1 HL60570, UO1 HL60571, UO1 HL60573, UO1 HL60574, and UO1 HL62828.