Performance After Naps in Sleep-Conducive and Alerting Environments.
Dinges-DF; Orne-EC; Evans-FJ; Orne-MT
NIOSH 1981 Jul:677-692
The effect of napping and environment alertness on reaction time and cognitive performance was studied. Subjects were 18 to 36 years old, 36 males and 31 females. After 5 minutes of relaxing light activity, subjects went to sleep and were awakened by phone. The duration of napping was not known to subjects. After precisely 60 minutes, whether subjects were awake or asleep, a 72 decibel (dB) bell rang continuously and a small light appeared by the phone. Subject then performed a descending subtraction task (DST). The phone signaled the end of the period. Nap on day two was identical to the first day except that the environment simulated the noisy conditions of a home or dormitory. There were approximately 48 periods of sound in the 60 minute nap period. DST was performed before and after a 60 minute wake control period. In the DST task, subjects were asked to subtract a one digit number from a three digit number and say the answer aloud. Reaction time (RT) was slower and DST accuracy lower on day one. On day two, RT and DST were slower at after the nap, however, DST accuracy was not significantly lower. On both days, RT to bell signaling was longest for subjects in stage 4 sleep. Cognitive functioning was not affected by stage 4 sleep at the time of awakening. On day one, there was a steady decrease in DST performance as sleep length increased. Post nap performance on day two was equal to pre nap performance even after short nap periods. Performance level was 26 percent below the pre nap level in subjects who slept longest and was equivalent to that on day one. The amount of stages 2+3+4 sleep appeared to be the major predictor of DST decrement. Only subjects who had been awake or in stage 1 more than 5 minutes before the bell had lower DST decrease. The authors conclude that even a small amount of afternoon sleep produces transient, but profound, decrements in cognitive performance.
Sleep-deprivation; Task-performance; Mental-fatigue; Psychological-effects; Psychophysiological-testing; Environmental-stress; Mental-stress; Humans;
The Twenty-Four Hour Workday: Proceedings of a Symposium on Variations in Work-Sleep Schedules, Division of Biomedical and Behavioral Science, NIOSH, U.S. Department of Health and Human Services, Cincinnati, Ohio, DHHS (NIOSH) Publication No. 81-127