Daytime Sleep Aids and Nighttime Cognitive Performance

Abstract : Air and ground crews are often given rest opportunities at atypical times, outside of a normal entrained circadian sleep period. Due to normal human biology, this practice often leads to delayed, thus shortened, sleep as well as restless sleep. In such cases, a sleep promoting or "No-Go" medication may be prescribed to promote a more restorative crew rest. This study compared two doses of the hypnotic zolpidem, two doses of melatonin and placebo for their effects on daytime sleep, on nighttime cognitive performance and on mood in an operationally and militarily relevant paradigm. The participants worked all night. Subsequently, an Early Group slept from 0800-1600 and a Late Group slept from 1400-2200. The participants worked all night again. Measures included polysomnography, simple and complex cognitive task performance, vigilance, subjective reports, salivary melatonin, and vital signs. Neither zolpidem nor melatonin was successful in improving daytime sleep compared to placebo. Participants slept longer under the medicated treatments, but it was not statistically significant. Sleep inertia was deepened by the use of zolpidem and may prolong degraded performance, sleepiness and fatigue. In this study, there were no advantages for morning or afternoon sleepers for nighttime alertness, mood or performance. The Foret & Lantin (1972) findings of 34 hours of sleep during the day do not appear to hold for sleep-deprived people sleeping under ideal conditions. For two consecutive work nights, ideal daytime sleeping conditions appear to provide nearly as much sleep as a sleep aid and without any risk to nighttime performance or side effects.