Borderline hypertension. A 24-hour abnormality.

It has recently been questioned whether borderline hypertension (BH) is a reality or just an artefact due to the person's knowledge of his or her raised blood pressure. This issue was evaluated by measuring ambulatory blood pressure (ABP) in subjects with BH, compared to normotensive individuals (NC). In particular, we wanted to investigate whether the basal blood pressure levels during sleep at night were elevated in BH subjects, or whether these individuals would normalize blood pressure during periods of low psychological arousal. Twenty-four-hour ABP was measured using the Spacelabs monitor 90202. Forty-nine BH subjects (systolic blood pressure [SBP] 140 to 160 mm Hg or diastolic blood pressure [DBP] 85 to 95 mm Hg) and 18 NC (SBP 110 to 130 mm Hg and DBP 60 to 80 mm Hg) were recruited from an unbiased population sample (age 20 to 28 years). The classification of BH and NC, respectively, was confirmed by intraarterial BP recordings. There was the expected variation of blood pressure throughout the 24 h (the highest values in the afternoon and lowest at night). SBP was significantly higher in the BH than in the NC group for the entire 24 h as well as during the four 6-h periods (morning P = .007, afternoon P < .001, evening P < .001, and night P = .025). A smaller but significant difference between the groups was seen for DBP but only in the afternoon and in the evening (morning P = .167, afternoon P = .022, evening P = .038, night P = .310).(ABSTRACT TRUNCATED AT 250 WORDS)