For the study, eight healthy people between the ages of 19 and 36 and of normal weight were studied for 16 days. The in-patient study consisted of a four-day acclimation period followed by nine days of sleep restriction. The sleep restriction consisted of four hours of sleep per night. Normal sleep consisted of nine hours of sleep per night. Three following days were allotted for recovery.
The patients also received 24-hour blood pressure monitoring at regular intervals to measure each study phase.
- During the nighttime, in the sleep restriction phase compared to the normal sleep phase, systolic (top number) and diastolic (bottom number) blood pressure averaged 115/64 millimeters of mercury (mm Hg) versus 105/57 mm Hg, respectively.
- The expected fall in blood pressure during the night was suppressed when subjects had inadequate sleep. They also found that nighttime heart rate was higher with sleep restriction than in normal sleep.
We know high blood pressure, particularly during the night, is one of the major risk factors for heart disease, and Americans typically do not get enough sleep, says lead author Naima Covassin, Ph.D., Mayo Clinic cardiovascular diseases research fellow. For the first time, we demonstrated that insufficient sleep causes increases in nighttime blood pressure and dampens nocturnal blood pressure dipping by using a controlled study that mimics the sleep loss experienced by many people.