Circadian variation in blood pressure: dipper or nondipper.

Awareness of an increased incidence of cardiovascular events shortly after awakening has heightened interest in the chronopathology of cardiovascular diseases. Blood pressure varies according to cycles characterized by a reduction during sleep and an increase on awakening. The surge in blood pressure coincides with the circadian nature of various endocrine and hematologic parameters that also have a putative role in triggering the onset of cardiovascular events. The nighttime decrease is absent or blunted in some hypertensive patients (termed nondippers), an effect associated with increased morbidity. Drugs can influence the effect of these circadian patterns. Research efforts are focused on clarifying an underlying pathophysiologic process that could be modified by pharmacologic or other means. Long-acting angiotensin II receptor blockers have an effect on blood pressure over 24 hours due to their long half-life, but could also limit the morning surge in blood pressure through an effect on the renin-angiotensin-aldosterone and noradrenergic systems.