The Effects of a Chronic Limitation of Sleep Length

Fifteen male subjects (Ss) were studied once each week while on a sleep regime of 5 1/2 hrs of sleep a night for 60 days. The electroencephalogram and electro-oculogram were recorded in the laboratory once each week. Performance was measured each week using the Wilkinson Vigilance Task, the Wilkinson Addition Test, and a word memory test, and grip strength was measured using a hand dynomometer. The Zung Depression Scale and the Gough Adjective Check List were used to measure mood. The Ss completed a sleep log on a daily basis. The effect on sleep of the restricted regime was to initially increase the absolute amount of stage 4 sleep. But by the 5th week of the study the stage 4 amount decreased to near baseline levels. The initial effect on REM sleep was to sharply reduce this type of sleep when compared with baseline values. During the course of the experiment there was a REM deprivation of some 25% of baseline values and 30 min in absolute amount. During the course of the experiment the latency to the onset of the first stage 4 and the latency to the first REM period were reduced. Only the Wilkinson Vigilance Task showed a decline in performance associated with continued restricted sleep. The sleep logs revealed that initially the Ss experienced difficulty in arousing from sleep in the morning and felt drowsy during the day, but these effects did not continue throughout the experiment. The mood scales showed no changes associated with continuing to sleep 5 1/5 hrs a night. These findings suggest that a chronic loss of sleep as much as 2 1/2 hours a night is not likely to result in major behavioral consequences.