A comparison of the twenty-four-hour blood pressure profile in normotensive and hypertensive subjects.

The aim of this study was to assess the relationship between blood pressure measured conventionally ('conventional' pressure) and 24 h ambulatory blood pressure measured with the SpaceLabs 90202 recorder, in a control population with normal blood pressure, and in patients with hypertension. Reference values for 24 h ambulatory blood pressure had been determined previously in a control population of 776 healthy bank employees (396 men and 380 women), aged 17-80 years, and were compared with those from a clinic population which comprised 805 patients referred to a blood pressure clinic for evaluation of hypertension. The clinic population was divided into two groups: 'normotensive' patients, whose conventional blood pressure was less than 160/90 mmHg (n = 168), and 'hypertensive' patients, whose conventional blood pressure was greater than or equal to 160/90 mmHg (n = 637). The clinic population had higher conventional (156/87 versus 119/76 mmHg), daytime (147/90 versus 125/79 mmHg) and night-time (129/75 versus 106/61 mmHg) ambulatory pressures compared with the control population. The clinic 'hypertensive' patients had higher conventional (175/97 versus 136/77 mmHg), daytime (153/93 versus 140/87 mmHg) and night-time (133/78 versus 124/72 mmHg) ambulatory pressures than the clinic normotensive population. Daytime ambulatory pressure was higher than conventional pressure (125/79 versus 119/76 mmHg) in the control population and in the clinic normotensive population (140/87 versus 136/77 mmHg). However, this relationship was reversed in the clinic hypertensive patients (153/93 versus 175/97 mmHg). It is concluded that while conventionally measured blood pressure tends to be lower than ambulatory daytime pressure in normotensive populations, this relationship is reversed in patients with hypertension.