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Blood pressures, pulse rates and 24-h urinary electrolyte content were measured in 371 male and 125 female randomly selected civil servants. The male and female subjects were divided into nine subgroups each, by tertiles of sodium (Na) excretion and tertiles of pulse rate. Those in the subgroup with highest values for both variables had the highest mean systolic and diastolic blood pressure (adjusted to age 50 years and a body mass index of 25 kg/m2) among the male and female groups, and those in the subgroup with lowest values for both variables had the lowest systolic pressure among the male and female groups and the lowest diastolic pressure of the female groups. Both systolic and diastolic blood pressure were significantly related to an interaction term between urinary Na excretion and pulse rate among males (P less than 0.02, P less than 0.03 respectively). These data support the hypothesis that psychological stress (assessed by pulse) and dietary sodium (assessed by sodium excretion) may interact to determine levels of blood pressure.

Whether a diuretic confers an additional antihypertensive effect on patients receiving treatment with calcium channel blocking drugs remains controversial. The results of seven recently reported trials are summarized, with the conclusion that much of the confusion arises because of inadequacies in trial design, particularly the failure to take into account placebo responses and period effect, and the inclusion of too few subjects to give the trial sufficient power to demonstrate a significant fall in blood pressure. Further difficulties in comparing one trial with another include differences with respect to age, race, severity of hypertension and renin status in the patient populations under investigation, since all these factors may influence responsiveness to therapy with both classes of agent. Although there may be theoretical grounds for believing that, under circumstances of optimal calcium entry blockade in vascular smooth muscle, diuretics might not cause any further reduction in blood pressure, until such time as full dose-response relationships are established for each class of agent alone and in combination, the problem will remain unresolved.

The conditions under which blood pressures (BPs) are recorded are critical, and it has been demonstrated several times that BPs measured in the home are lower than those measured in the clinic. However, these comparisons are based on home BPs measured by the patients or their friends and relatives and clinic BPs measured by doctors and nurses. To our knowledge, no comparison of home and clinic BPs measured by the same observer has been reported, and we present the results of such a study which is the first to demonstrate higher BPs in the home environment, perhaps reflecting the unacculturated nature of the study population.

The blood pressure patterns of three Kenyan communities have been studied: 861 members of the Luo tribe in a rural community, 281 members of the Kamba tribe in a rural community and 310 "urban" Luo living in Nairobi. The slope of linear regression of blood pressure with age was significantly different in each population: rural Luo had the smallest rise with age and urban Luo had the largest rise with age, while the Kamba tribe were in between. The differences could not be accounted for by weight. Urinary electrolyte data showed rural Luo had the lowest sodium ratios (sodium/creatinine, sodium/potassium) and the highest potassium/creatinine ratio: urban Luo had the highest sodium and lowest potassium ratios and rural Kamba had values in between. The differences in blood pressures between the two groups of the same tribe in different environments (rural and urban Luo) were far greater than those between different genetic groups (Kamba and Luo) underlining the importance of environmental factor(s) in the determination of arterial pressure. Furthermore, these data support the theory that the dietary intake of sodium and potassium are the major influential environmental factors affecting blood pressure.