on behalf of the Hypertension Detection and Follow-up Program Cooperative GroupThe Hypertension Detection and Follow-up Program followed up 10,940 persons for 5 years in a community-based, randomized, controlled trial of treatment for hypertension. Participants were randomized to one of two treatment groups, stepped care and referred care. The primary end point of the study was all-cause mortality, with morbid events involving the heart, brain, and kidney as secondary end points. Loss of renal function, ascertained by a change in serum creatinine, was among these secondary events. Baseline serum creatinine concentration had a significant prognostic value for 8-year mortality. For persons with a serum creatinine concentration greater than or equal to 1.7 mg/dl, 8-year mortality was more than three times that of all other participants. The estimated 5-year incidence of substantial decline in renal function was 21.7/1,000 in the stepped-care group and 24.6/1,000 in the referred-care group. Among persons with a baseline serum creatinine level between 1.5 and 1.7 mg/dl, the 5-year incidence of decline was 113.3/1,000 (stepped care) and 226.6/1,000 (referred care) (p<0.01). The incidence of decline in renal function was greater in men, blacks, and older adults, as well as in those with higher entry diastolic blood pressure. Among persons with a baseline serum creatinine level greater than or equal to 1.7 mg/dl, serum creatinine concentration declined by 25% or more in 28.6% of stepped-care and 25.2% of referred-care participants. Although the incidence of clinically significant hypercreatininemia in a hypertensive population is low, an elevated serum creatinine concentration is a very potent independent risk factor for mortality. The slightly lower rate of development of hypercreatininemia and the higher rate of improvement in stepped-care compared with referred-care participants is consistent with the belief that aggressive treatment of hypertension may reduce renal damage and the associated increased risk of death. (Hypertension 1989;13(suppl I):I-80-1-93) H ypertension is one of the most common adult chronic diseases for which treatment is available. The disease affects all race, sex, and age groups but has a markedly higher prevalence among blacks 1 and a concomitantly higher mortality from its sequelae. 2 The risk associated with hypertension includes fatal and nonfatal outcomes

340-346, 1987. MANY epidemiologic studies have identified blood pressure as an important risk factor for both cardiovascular disease and total mortality. 12 Elevated levels of either diastolic blood pressure (DBP) or systolic blood pressure (SBP) are associated with an increased mortality risk. As a result of these findings, the importance of the detection and treatment of individuals with high blood pressure has been established.Several pressure measures have been used to improve predictability of subsequent cardiovascular morFrom the Hypertension Detection and Follow-up Program, The

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Single- vs multiple-day food records were compared for estimates of intake for sodium, potassium, and calories; and the correspondence was assessed between sodium and potassium intake and 24-h urinary excretion. Fifty-five middle-aged adults, participating in a prerandomization assessment for a nutritional/behavioral intervention program on blood pressure completed a six-day food record and a 24-h urine collection. The group average for sodium, potassium, and calories obtained from one-day food records proved to be as good an estimate of the six-day average as did values from multiple day records. Similarly the one-day food record proved a good estimate of the mean 24-h urinary values for sodium and potassium. If properly collected and analyzed, a one-day food record is a good estimate of a population's intake of sodium and potassium while multiple days of recording are necessary to characterize individual intake.

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Phase 1 of the Trials of Hypertension Prevention was conducted in 2182 adults, aged 35-54 y, with diastolic blood pressure of 80-89 mm Hg to test the feasibility and blood pressure-lowering effects of seven nonpharmacologic interventions (weight loss, sodium reduction, stress management, and supplementation with calcium, magnesium, potassium, and fish oil). At 6 and 18 mo, weight loss and sodium reduction were well-tolerated and produced significant declines in systolic and diastolic blood pressures (-2.9/-2.4 and -2.1/-1.2 mm Hg for weight loss and sodium reduction, respectively, at 18 mo). None of the other interventions lowered blood pressure significantly at either the 6- or 18-mo follow-up visits. These results suggest that both weight loss and sodium reduction provide an effective means to prevent hypertension. The long-term effects of both of these interventions are being tested in phase 2 of the trial.

The strong geographic and social class differences in blood pressure may be related to differences in potassium intake or in the ratio of sodium to potassium intake. "Low salt" populations also have high potassium intake. In Japanese villages, populations with similar salt intake but different blood pressures had different potassium intake. In one study, a significant correlation was found between urinary Na/K ratio and blood pressure. Another study showed a significant negative correlation between potassium excretion and blood pressure. Four studies are available that show that blacks excrete much less potassium than whites. One of these studies also showed, by analyzing duplicate meals, that blacks consumed much less potassium than whites. A high potassium diet tends to be more expensive than a low potassium diet. Potassium intake may be a major factor in the epidemiologic differences of hypertension.

Blood pressure variability is an important consideration in hypertension trials for determining required sample size and consequently making accurate outcome statements. The Hypertension Prevention Trial was a randomized controlled trial carried out in 1983-1986 in four US clinics on men and women with high normal diastolic blood pressure. This trial provided an opportunity to assess conditions affecting blood pressure measurement variability. Trained blood pressure observers measured systolic and diastolic blood pressures twice, 30 seconds apart, using a random-zero sphygmomanometer. The quality of blood pressure measurements was assessed by computing the variability of the two readings per participant-visit for each blood pressure observer at each study clinic. Other sources of variability investigated included observer digit preference, time of day, and ambient temperature. On the basis of data from this population, it is estimated that the standard deviation of blood pressure values can be reduced by 5% by taking two measurements per participant-visit. An additional reduction of variability can be effected by having the duplicate blood pressure measurements made by different blood pressure observers. In special instances where the range of blood pressure values is very restricted, use of the random-zero sphygmomanometer can increase or decrease the among-participant variability in blood pressure values, depending upon where the distribution of blood pressure values is centered.