THE RELATIONSHIP BETWEEN SLEEP-DEPRIVATION AND THE NOCTURNAL DECLINE OF BLOOD-PRESSURE

Blood pressure (BP) has a circadian pattern with a 10% to 15% drop in systolic and diastolic BP comparing nighttime and daytime averages. Th e mechanism and the ''reason'' for the decline of nocturnal blood pres sure has not been described. If the nocturnal decline is a restorative physiologic process we reasoned that sleep deprivation would increase the nocturnal drop. Thus, we tested the hypothesis that there is a co mpensatory decline in nocturnal sleep blood pressure after a period of nocturnal sleep deprivation. Twenty-four house staff personnel (normo tensive and not taking any BP medications) with a mean age of 29.3 yea rs were recruited for this study (13 men and 11 women). Subjects were randomly assigned to have 24-h BP monitoring after being sleep deprive d (on call with 3 +/- 1.3 h of sleep) or after a normal night's sleep (7.3 +/- 0.8 h). There was no significant difference in hours asleep o r time to bed or time awake for both 24-h studies. Subjects had simila r activities for both monitoring intervals. The percent change in day awake versus night asleep mean values for systolic BP, diastolic BP, a nd mean arterial pressure for sleep deprived and normal night's sleep intervals were compared using paired t tests. None of these paired par ameters were significantly different despite a subjectively ''deeper'' sleep postcall. In conclusion, sleep deprivation does not appear to r esult in a compensatory decline in nocturnal blood pressure. Thus, the ''reason'' for the normal nocturnal decline in blood pressure remains to be explored.