Sleep deprivation and naps

It is important for military commanders to know the likely effects of a small amount of sleep under conditions of sustained operations. To this end, two laboratory-based experiments on naps were carried out. The first examined the effect of 2 h of sleep following 90 h of wakefulness. Ten infantrymen subjects were not told the scheduled length of their vigil, or that they would be allowed a nap at some stage, until a few hours before the 2-h nap. After 3 nights without sleep, the subjects’ average cognitive performance was 55% of the control values. During a test session immediately before the 2-h nap, performance improved by 30%, to 85% of control values, indicating the considerable effect that the incentive of knowing that a nap is imminent can have on even severely sleep-deprived subjects. In the second experiment, two groups, each of six infantrymen, took part in a 5-day trial; for one group, 4 h of uninterrupted sleep was scheduled and for the other, four l-h naps in each 24-h period. There were no significant differences in cognitive test scores or mood between the two groups. On the last experimental day, cognitive test and mood scores were not significantly different from baseline values for either group, indicating the utility of 4 h of sleep, either in one uninterrupted block or in four scheduled 1-h naps per 24 h.