The Trials of Hypertension Prevention, Phase II - TOHP II
TOHP II was a multicenter, randomized trial with a 2x2 factorial design, designed to test the efficacy of interventions to promote weight loss, sodium reduction, and the combination of weight loss and sodium reduction in decreasing diastolic blood pressure (BP), systolic BP, and the incidence of hypertension during a three- to four-year follow-up period in moderately overweight men and women with a high-normal level of diastolic BP.
In overweight adults with high-normal BP, weight loss and reduction in sodium intake are effective interventions in lowering systolic and diastolic BP.
Patients Enrolled: 2,382
Mean Follow Up: 36-48 months
Screening efforts were directed at recruiting healthy, moderately overweight, 30- to 54-year-old men and women with a high-normal diastolic BP. To be eligible, the cumulative average of a candidate's diastolic BP readings at three screening visits had to be within the following ranges: 81-97 mm Hg at screening visit 1, 82-92 mm Hg at screening visit 2, and 83-89 mm Hg at screening visit 3. In addition, participants had to have a body mass index within a range of 26.1-37.4 kg/m for men and 24.4-37.4 kg/m for women.
Current hypertension (including systolic BP ≥140 mm Hg) or treatment with medications that might affect BP, clinical or laboratory evidence of cardiovascular disease, diabetes mellitus, renal insufficiency (serum creatinine level ≥150 mcmol/l [1.7 mg/dl] for men and ≥133 mcmol/l [1.5 mg/dl] for women), or another serious illness, current or planned pregnancy, and evidence of unwillingness or inability to adhere to the trial intervention or data collection procedures
Net change in diastolic BP from baseline to termination visits
Change in systolic BP at termination and incidence of hypertension during follow-up
Moderately overweight individuals with high-normal diastolic BP were randomly assigned to one of four treatment groups: weight loss alone, sodium reduction alone, weight loss plus sodium reduction (combined), or no active intervention (usual care). Participants were followed up for 36-48 months, with a net change in diastolic BP from baseline to termination visits designated as the primary outcome measure.
A total of 2,382 men and women were randomly assigned to combined weight loss and sodium reduction (group A, n=597), weight loss (group B, n=595), sodium reduction (group C, n=594), and usual care (group D, n=596). Baseline characteristics were similar among groups. Compared with the usual care group at six months, the BP reductions for the weight loss, sodium reduction, and combined groups were 3.7/2.7 mm Hg, 2.9/1.6 mm Hg, and 4.0/2.8 mm Hg, respectively (p<0.001 for all). All intervention groups had significant changes in the diastolic BP measurements at six months compared to the usual care group (-2.7 ± 0.4 for the weight loss group, p<0.001, -1.6 ± 0.4 for the sodium reduction group, p<0.001 and -2.8 ± 0.4 for the combined group, p<0.001).
At 18 months, the BP reductions of the active intervention groups compared with those of the usual care group were somewhat less than at six months—each about 2/1 mm Hg—but all remained statistically significant (p<0.003). By 36 months, the BP changes were further reduced in each active intervention group compared with the usual care group and were statistically significant for diastolic BP only in the weight loss group (-0.9 mm Hg, p<0.04). At six months, the incidence of hypertension was highest in the usual care group (7.3%), intermediate in the weight loss (4.2%) and sodium reduction (4.5%) groups, and lowest in the combined group (2.7). By 48 months, the incidence of hypertension was quite similar in the three active intervention groups (approximately 38%), and in each case was lower than in the usual care group (44%) (p=0.02-0.06).
Among overweight adults with high-normal BP, weight loss, and reduction in sodium intake, individually and in combination, were effective in lowering systolic and diastolic BP, especially in the short-term (six months). Although the effects on average BP declined over time, reductions in hypertension incidence were achieved.
The intervention programs in TOPH II were successful in the short-term and showed significant effects on BP-related outcomes. Each effect, however, decreased with continued follow-up, and the primary endpoint—change in diastolic BP at 36 months—was not significantly affected by weight loss or sodium reduction in main effects analysis or by the combined intervention. Incidence of hypertension, a secondary endpoint, was significantly reduced by each intervention program in the short-term (six months).
Effects of weight loss and sodium reduction intervention on blood pressure and hypertension incidence in overweight people with high-normal blood pressure. The Trials of Hypertension Prevention, phase II. The Trials of Hypertension Prevention Collaborative Research Group. Arch Intern Med 1997;157:657-67.
Keywords: Outcome Assessment (Health Care), Behavior Therapy, Follow-Up Studies, Body Mass Index, Sodium, Dietary, Overweight, Weight Loss, Blood Pressure, Diet, Hypertension, Systole
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