A University of Pittsburgh study has found that stressed sleepers wake more frequently while sleeping and have fewer periods of deep sleep. Although the connection between daytime stress and restless sleep has been proven, researchers are still investigating the exact ways stress affects sleep.
In the study, the researchers monitored the heart rates of 59 healthy undergraduate students while they slept. Variations in heart rates can give clues regarding the activity of the involuntary nervous system, which directs the function of organs such as the heart and lungs. To initiate stress during sleep, the researchers told half of the students that they would have to give a 15-minute speech when they woke up and that the topics would be given to them upon awakening.
The researchers noticed dramatic heart rate differences between the stressed and nonstressed students as they slept. The stressed group had changes in heart rate patterns during rapid-eyemovement (REM) sleep and non-REM sleep.
Because the heart rate variability patterns observed in the stressed students were similar to those witnessed in individuals with insomnia, these results suggest similar pathways of nervous system disruption. (These findings were reported in Psychosomatic Medicine, January/February 2004.)