Baseline characteristics of participants in phase II of the Trials of Hypertension Prevention (TOHP II)

Phase II of the Trials of Hypertension Prevention (TOHP II) is a multicenter, controlled clinical trial designed to test whether weight loss, a reduced sodium intake, or a combination of weight loss and a reduced sodium intake will lower blood pressure (BP) and prevent the occurrence of hypertension. The study population consists of middle-aged, moderately overweight individuals with a diastolic BP between 83 and 89 mm Hg. Of the 2382 randomized participants, 816 (34%) are female and 494 (21%) are from a racial or ethnic minority background. At baseline, mean dietary intakes of sodium, based on measurements of 24-hour urinary excretion, were 199 mmol/d in men and 154 mmol/d in women. The average body mass index was 30.9 kg/m2. Across the four randomized groups, there was no substantial imbalance in the distribution of baseline variables; however, the mean age in the four groups was slightly but significantly different (range: 43.2 to 44.2 years, P = 0.02). A comparison of baseline characteristics of TOHP II participants with those of participants in three other primary prevention trials reveals a high level of mean dietary sodium intake in each study. Data reported in this article indicate that any subsequent differences in BP among the randomized groups are unlikely to result from maldistribution of known confounding variables at baseline. Finally, because of the high prevalence of overweight and excessive sodium intake in the United States, results from TOHP II should be broadly applicable to the general population.