Circadian rhythms in hypertension.

Continuous intra-arterial blood pressure recordings have been performed in 37 untreated ambulatory hypertensive subjects, who were investigated on an outpatient basis. Hourly data analysis demonstrated a circadian variation of both blood pressure and heart rate which were highest during the morning and fell during the late afternoon to reach a nadir during sleep. Prior to waking there was an increase in blood pressure, but not heart rate; however both blood pressure and heart rate increased briskly shortly after waking. Chronic therapy with oxprenolol (in 10patients) reduced daytime blood pressure, but had little effect during the night-time or early morning.