Ambulatory Blood Pressure in Clinical Practice: Clinical Relevance of Circadian Rhythm and Nocturnal Dip

Blood pressure (BP) variability and terms like dipper and nondipper are now common in daily practice. Several mechanisms underlie abnormalities in circadian variability. Sympathetic overactivity, reduced sensibility of baroreceptors, volume overload, and primary or secondary autonomic dysfunction are the most important factors related to abnormalities in circadian variability. The level of nighttime BP drop has been related to the absolute level of BP elevation, the global cardiovascular risk, the presence of comorbidities, and the type and time of administration of antihypertensive treatment. The relative importance of circadian variability or nocturnal BP as a prognostic factor raise not only academic interest but also clinical utility. Abnormal circadian variability indicates the presence of underlying organ damage, but BP itself should be the target for antihypertensive therapy. Furthermore, excessive BP drop during sleep has been associated to a higher risk for cerebral and/or retinal ischemia.