Sodium reduction for hypertension prevention in overweight adults: further results from the Trials of Hypertension Prevention Phase II

Sodium reduction is efficacious for primary prevention of hypertension, but the feasibility of achieving this effect is unclear. The objective of the paper is detailed analyses of adherence to and effects of the sodium reduction intervention among overweight adults in the Trials of Hypertension Prevention, Phase II. Sodium reduction (comprehensive education and counselling about how to reduce sodium intake) was tested vs no dietary intervention (usual care) for 36-48 months. A total of 956 white and 203 black adults, ages 30-54 years, with diastolic blood pressure 83-89 mmHg, systolic blood pressure (SBP) <140 mmHg, and body weight 110-165% of gender-specific standard weight were included in the study. At 36 months, urinary sodium excretion was 40.4 mmol/24 h (24.4%) lower in sodium reduction compared to usual care participants (P<0.0001), but only 21% of sodium reduction participants achieved the targeted level of sodium excretion below 80 mmol/24 h. Adherence was positively related to attendance at face-to-face contacts. Net decreases in SBP at 6, 18, and 36 months of 2.9 (P<0.001), 2.0 (P<0.001), and 1.3 (P=0.02) mmHg in sodium reduction vs usual care were associated with an overall 18% lower incidence of hypertension (P=0.048); were relatively unchanged by adjustment for ethnicity, gender, age, and baseline blood pressure, BMI, and sodium excretion; and were observed in both black and white men and women. From these beneficial but modest results with highly motivated and extensively counselled individuals, sodium reduction sufficient to favourably influence the population blood pressure distribution will be difficult to achieve without food supply changes.

Trials of Hypertension Prevention, phase II. Structure and content of the weight loss and dietary sodium reduction interventions. Trials of Hypertension Prevention (TOHP) Collaborative Research Group

Identifying effective, nonpharmacologic means of preventing or significantly delaying the onset of hypertension would be a major advance in the primary prevention of cardiovascular disease. In the first phase of the Trials of Hypertension Prevention (TOHP I), adults with high-normal diastolic blood pressure were randomly assigned to one of seven nonpharmacologic interventions. Only weight loss and reduction of dietary sodium proved to be effective strategies for reducing blood pressure. The second phase of TOHP (TOHP II) will test the effectiveness of weight loss, reduction of dietary sodium, and their combination of lowering blood pressure and preventing the onset of hypertension over a 3- to 4-year follow-up period. This article describes the three interventions used in TOHP II, methods used to maintain continued participation in this long-term trial, and protocol enhancements designed to maximize intervention effectiveness.

Feasibility and efficacy of sodium reduction in the Trials of Hypertension Prevention, phase I. Trials of Hypertension Prevention Collaborative Research Group

Phase I of the Trials of Hypertension Prevention was a multicenter, randomized trial of the feasibility and efficacy of seven nonpharmacologic interventions, including sodium reduction, in lowering blood pressure in 30- to 54-year-old individuals with a diastolic blood pressure of 80 to 89 mm Hg. Six centers tested an intervention designed to reduce dietary sodium to 80 mmol (1800 mg)/24 h with a total of 327 active intervention and 417 control subjects. The intervention consisted of eight group and two one-to-one meetings during the first 3 months, followed by less-intensive counseling and support for the duration of the study. The mean net decrease in sodium excretion was 43.9 mmol/24 h at 18 months. Women had lower sodium intake at baseline and were therefore more likely to decrease to less than 80 mmol/24 h. Black subjects were less likely to decrease to less than 80 mmol/d, independent of sex or baseline sodium excretion. The mean (95% confidence interval) net decrease associated with treatment was -2.1 (-3.3, -0.8) mm Hg for systolic blood pressure and -1.2 (-2.0, -0.3) mm Hg for diastolic blood pressure at 18 months (both P < .01). Multivariate analyses indicated a larger systolic blood pressure effect in women (-4.44 versus -1.23 mm Hg in men), adjusted for age, race, baseline blood pressure, and baseline 24-hour urinary sodium excretion (P = .02). Dose-response analyses indicated an adjusted decrease of -1.4 mm Hg for systolic blood pressure and -0.9 mm Hg for diastolic blood pressure for a decrease of 100 mmol/24 h in 18-month sodium excretion. These results support the utility of sodium reduction as a population strategy for hypertension prevention and raise questions about possible differences in dose response associated with gender and initial level of sodium intake.

Dietary assessment in children using electronic methods: telephones and tape recorders

Selection of dietary assessment methodology is important in dietary intervention studies. Few studies have reported the relative merits of various assessment methods or the feasibility of electronic methods in pediatric populations. Parent-child dyads performed telephone recalls (no. = 32) and tape recorded dietary records (no. = 33). Traditional recalls were first conducted to familiarize parents and children with the telephone recall procedure, to introduce two-dimensional food models, and to instruct on the use of the tape recorder. Parents monitored and documented as unobtrusively as possible the child's intake on the day before the telephone recall and also on the day of the taped record. Children were called at random to reduce bias. Simple correlation coefficients (r) were calculated for nine nutrients and calories for both methods. For telephone recalls, values ranged from a low of r = .64 for saturated and polyunsaturated fat to r = .85 for cholesterol and r = .93 for iron. Tape-recorded data yielded r = .80 or above, except calories with r = .68 (p less than .001 for all values, 1-tail tests). Mean nutrient values were within expected ranges, e.g., 1,800 kcal +/- 500, with saturated fat about 14% of calories per day. Comparisons between parents and childrens reports of food frequencies and portion sizes revealed the best correlations for beverages, bread-cereals-crackers, meat-fish-poultry, and mixed dishes. We conclude that preadolescent children are able to provide dietary intake data using electronic methods in a manner that compares favorably with their parents' written records.

Effects of antihypertensive therapy on blood pressure control, cognition, and reactivity. A placebo-controlled comparison of prazosin, propranolol, and hydrochlorothiazide

A randomized, placebo-controlled trial was conducted to compare the effects of treatment with prazosin, propranolol, or hydrochlorothiazide on the following variables: blood pressure, cognitive and psychomotor skills, cardiovascular reactivity to natural and laboratory challenges, and serum lipid and lipoprotein levels. Side effects were recorded and patients evaluated how they felt during their treatment. Sixty-nine men, 35 percent black, aged 25 to 55 (mean 51.3) years, with diastolic blood pressures between 90 and 104 mm Hg (mean, 93.3 mm Hg), completed the study. There were no differences between active treatment groups in the proportion of patients with controlled blood pressure during the maintenance phase of the study. In the cognitive and psychomotor tests, the hydrochlorothiazide group showed significantly less improvement from baseline than the other treatment groups on the block design subscale of the Wechsler Adult Intelligence Scale-Revised, and there was a trend for the propranolol group to have less improvement from baseline than the other groups on the digit span subscale. There were no other significant pretreatment to post-treatment changes in the other cognitive or psychomotor tests, the Russell Revision of the Wechsler Memory Scale, or a number of computerized reaction-time and signal-detection tasks. In the reactivity testing, there was a significantly lower increase in heart rate in the prazosin group compared with placebo during the second laboratory challenge of the Stroop Color Interference Test. Post-treatment declines in ambulatory blood pressure were seen in all of the drug treatment groups in average and maximal diastolic and systolic blood pressures. Both propranolol and hydrochlorothiazide treatment resulted in low-density lipoprotein cholesterol levels that were higher than baseline and the hydrochlorothiazide treatment had significantly increased total cholesterol levels. In contrast, the prazosin-treated group experienced no adverse changes in these parameters. Overall, the propranolol group had significantly more moderate and severe side effects than did the other three groups. Considering the pattern of blood pressure control, cognitive and psychomotor effects, changes in lipid levels, and magnitude of side effects, prazosin seems to have the most advantageous profile in this study of the three anti-hypertensive agents evaluated.

Prazosin versus hydrochlorothiazide as initial antihypertensive therapy in black versus white patients

A randomized, drug-controlled trial was conducted to evaluate the comparative efficacy of hydrochlorothiazide versus prazosin in controlling mild diastolic hypertension in black and white patients. Serum lipid and lipoprotein levels were also studied. Overall, 22 men and 14 women, of whom 50 percent were black, aged 21 to 69 years, were randomly assigned to treatment with either of these two agents. If diastolic blood pressure was not reduced below 90 mm Hg, the other agent was added. Results showed that hydrochlorothiazide and prazosin lowered blood pressure effectively in both black and white patients, but there was a trend for more patients receiving hydrochlorothiazide to need combination therapy than for those receiving prazosin, regardless of ethnic status. Prazosin therapy reduced total cholesterol levels by 20.5 mg/dl and low-density lipoprotein cholesterol levels by 19.0 mg/dl, and hydrochlorothiazide increased total cholesterol levels by 11.4 mg/dl and increased low-density lipoprotein levels by 9.3 mg/dl; but no differences in triglyceride, high-density lipoprotein, plasma high-density lipoprotein2, or high-density lipoprotein3 levels were noted. Both agents were well tolerated in black and white patients. The combination of effective blood pressure control with no adverse effects on the serum lipid profile may make prazosin preferable to hydrochlorothiazide for treating mild diastolic hypertension in black as well as white patients.