REPRODUCIBILITY OF THE CIRCADIAN BLOOD-PRESSURE FALL AT NIGHT IN HEALTHY-YOUNG VOLUNTEERS

The aim of this study was to evaluate the reproducibility of the circa dian blood pressure (BP) change in normal healthy volunteers. The subj ects were 32 healthy, young, normotensive volunteers who underwent 24 h ambulatory Up monitoring on two occasions, at least 4 weeks apart. D ata were analysed using standard definitions of day and night tie 07.0 0-22.00 for daytime and 22.00-07.00 for night time), event diaries to identify individual's day and night time and a time independent method (cusum analysis), Intraindividual variations of BP were assessed usin g the coefficient of variation (CV). The mean 24 h Up was very reprodu cible with a CV of 4.7%. Using the fixed definition of day and night, mean night time systolic blood pressure (SEP) was significantly reduce d on the second visit compared to the first (P < 0.001). Using fixed t imes for day and night, day-night difference was poorly reproducible, with a CV of 52% for Sap and 59% for diastolic blood pressure (DBP), h owever this improved using diary based day-night to 40/41% and cusum a nalysis to 24.6/28.1%. We recommend that circadian BP changes are stud ied using individual definitions of day and night or time independent methods such as cusum analysis.