Understanding Sleep Regulatory Processes to Improve Waking Performance

Abstract

Both sleepand waking performance are regulated by the interaction of two processes: the hoeostatic process that tracks the increase of sleep pressure during wakefulness and its discharge during sleep; the circadian process that generates cyclic changes in the drive for wakefulness. During normal entrainment to the light/dark cycle, the homeostatic and circadian process counteract each other, allowing humans to maintain adequate performance for ~ 16 h during daytime, and consolidate sleep for ~ 8 h at nighttime. In the modern 24-h society, however, many indiviuals are required to work and sleep under conditions in which the relatinship between homeastatic and circadian processes is substantially altered, generating a dangerous landscape for failures and errors in operational situations. Conversely, understanding the interaction of homeostatic and circadian processes can be used to develop countermeasures against poor sleep and impaired performance. In a simulated shift work protocol we tested whether a daly in the timing of the typical morning sleep episode into the afternoon - combined with a light-induced circadian phase advance - can reduce homeostatic sleep pressure during the subsequent night shift. We found that, indeed, on such a schedule individuals show fewer attentional errors during the night shift compared to a traditional sleep schedule experienced by many shift workers. Shift workers also have difficulties maintaining sleep during the daytime, because the decrease in their circadian wke drive by judiciously-timed melatonin administration. We showed that transdermal melatonin delivery con gradually increase plasma melatonin concentrations and thereby improve sleep efficiency in the latter part of an 8-h daytime sleep opportunity. These and other recent studies indicate that insight into the specific interaction of homeostatic and circadian processes can help researchers devise new strategies for counteracting impairments of sleep and performence in individuals in operational settings.