Behavioral and psychological correlates of a difference in chronic sleep duration.

The relationship between chronic differences in sleep duration and waking behaviors was explored by comparing two groups of 10 healthy male university students who regularly slept nocturnally for 7-8 h or for 9.5-10.5 h. Measurements were obtained of sublingual temperature, from a 45 min Wilkinson auditory vigilance task and a mood adjective check list 30 min after awakening in the morning, at midday ind in the early evening following an electroencephalographically recorded night of sleep. In both subject groups body temperature increased from morning to early evening, while misses on the vigilance task correspondingly declined during the day. The average daily level of oral temperature and performance were significantly lower in the 7-8 h (control) group than in the long sleepers. Positive mood states (Cheerful, Energetic, General Activation, High Activation) were significantly greater and negative affects (Anger-Hostility, Depression) significantly less in the long sleepers. As a result of the mean difference in total sleep time existing between groups control subjects averaged significantly less stage 2, and stage REM sleep. It was postulated that there were behavioral deficits in the control group attirbutable either to selective sleep stage deprivation or to the general consequence of reduced sleep per se or to both of these factors.