Electronic activity-monitor-derived sleeping and awake times and diurnal variation of blood pressure

Background Results of a number of studies have indicated that target-organ damage is more pronounced in non-dippers, those in whom the blood pressure falls by less than 10% with the onset of sleep, than it is in dippers with comparable clinic blood pressures. However, the standard use of arbitrarily defined daytime and night-time periods, rather than precise estimates of s leeping time and awake time, could limit the accuracy of estimates of diurn al variation of blood pressure and hence of dipping status. Design and methods In this study of 102 consecutive patients undergoing amb ulatory blood pressure monitoring we compared activity-derived estimates of sleeping and awake blood pressures using electronic activity monitoring an d diary records with estimates determined using pre-defined day and night-t ime periods. The dipping/non-dipping status of each subject was assessed us ing these three different techniques for defining the awake/asleep time per iods, Results The sleeping/awake times based on the activity monitor, diary and d efault data were 2356 h +/- 55 min/0754 h +/- 50 min, 2326 h +/- 61 min/072 2 h +/- 72 min and 2300 h and 0700 h respectively. The percentage systolic/ diastolic falls in blood pressure were 18 +/- 61 18 +/- 7% with six non-dip pers (activity-monitor-derived data), 16 +/- 6/17 +/- 8% and 12 non-dippers (diary data) and 13 +/- 7/15 +/- 7% and 21 non-dippers (using the pre-set daytime and night-time periods), Discussion Results of this study demonstrate that the extent of the diurnal Variation in blood pressure (and hence dipping status) can differ dependin g on the technique used to define periods of wakefulness and sleep, (C) 200 0 Lippincott Williams & Wilkins.