Nocturnal blood pressure epidemiology, determinants, and effects of antihypertensive therapy.

It has been established that blood pressure and heart rate have a reproducible circadian pattern characterized by a low period during sleep; an early morning, post-awakening rise; and a high plateau period while a subject is awake. This rhythm is influenced by extrinsic (lpar;environmental) and intrinsic (physiologic and pathophysiologic) factors. When hypertensive patients have the typical circadian pattern of blood pressure described above, they are referred to as 'dippers', whereas, when the normal nocturnal fall of blood pressure is diminished or blunted,s the term 'nondipper' is applied. Cross-sectional and prospective data have shown that nondippers have more target-organ damage than have dippers. Therefore, the prognostic implications of the nondipper status may be important since the overall 24 h blood pressure load is elevated in these individuals. Assessing the effects of antihypertensive therapy on 24 h blood pressure and heart rate using ambulatory monitoring has become routine in clinical trials. However, the methods of analysis and tyipes of trial design may significantly affect evaluation of therapeutic effects on nocturnal blood pressure. This article describes the influence of analysis on 24 h blood pressure measurement especially insofar as it pertains to nocturnal (or sleep) blood pressure values.