Reference values for the ambulatory blood pressure and the blood pressure measured at home: a population study.

In order to determine reference values for the ambulatory blood pressure, a population sample of 328 subjects, aged 20-81 years, who reported themselves to be in good health, was investigated. The ambulatory blood pressure was recorded over 24 h, taking measurements at 20 min intervals from 8 am to 10 pm, and at 45 min intervals from 10 pm to 8 am. Blood pressure was also measured by trained observers on each of two separate home visits (5 readings per visit). The ambulatory blood pressure in the 328 subjects averaged 118/71 mmHg over 24 h, 124/76 mmHg during the day (10 am-8 pm), and 108/62 mmHg at night (0 am-6 am). Blood pressure measured by an observer at the occasion of the second home visit was 4/5 mmHg lower (P less than 0.001) than the daytime ambulatory blood pressure. The 95th centiles for the daytime ambulatory pressures were 144/95 mmHg in 85 men below age 50; 154/90 mmHg in 74 men aged greater than or equal to 50 years; 132/85 mmHg in 96 women below age 50; and 151/91 mmHg in 73 women aged greater than or equal to 50 years. The 95th centiles for the nighttime pressures in these four sex-age groups were 124/79, 140/83, 121/70, and 132/72 mmHg, respectively.