[The day-night changes in ambulatory blood pressure: another risk indicator in hypertension?]

In many different clinical situations, including some cases of secondary hypertension, nighttime blood pressure (BP) is abnormally increased in the majority of patients, with consequent flattening of the 24-hour BP profile, but the clinical importance of this finding in such conditions is unknown. In patients with essential hypertension, ambulatory BP has been shown to decrease by 10-20% from day to night, but in severe or malignant hypertension this diurnal BP rhythm may be blunted or even abolished. One of the reasons why the noninvasive monitoring of BP may be a reliable tool in assessing the day-night BP changes is the demonstration that frequent cuff inflations do not interfere to a significant extent with the haemodynamic effects of sleep. Part of the differences between the studies in the reported day-night BP drop may be artifactual, owing to the very different time intervals defining the daytime and nighttime subperiods in the single studies. In unselected patients with essential hypertension, a sizable proportion of subjects (17 to 40%) shows abnormally high nighttime BP, with consequent flattening of the 24-hour BP profile (the so called "non dippers", as opposed to the "dippers" who show a maintained diurnal BP rhythm). Several clinical studies carried out in independent laboratories show that the target organ damage induced by hypertension (left ventricular hypertrophy, cerebrovascular lesions) is more severe in hypertensive "non dippers" than in "dippers", possibly because of the different duration of exposure to high BP levels over the 24 hours.(ABSTRACT TRUNCATED AT 250 WORDS)