Effects of sleep deprivation in space
Studies, which include laboratory investigations (Category I) and field evaluations (Category II and Category III) of population groups that are analogous to astronauts (e.g., medical and aviation personnel), provide compelling evidence that working long shifts for extended periods of time contributes to sleep deprivation and can cause performance decrements, health problems, and other detrimental consequences, including accidents, that can affect both the worker and others.
A meta-analysis (Category I) that was conducted by Pilcher and Huffcutt [1] examined data that were drawn from 19 research studies to characterize the effects of sleep deprivation on specific types of human performance.
The neurobehavioral assessment battery that was used in the Van Dongen et al.[15] study included the psychomotor vigilance task (PVT).
[16] The PVT detects changes in basic neurobehavioral performance that involve vigilant attention, response speed, and impulsivity; and it has been extensively validated in ground-based laboratory studies to detect cognitive deficits that are caused by a variety of factors (e.g., restricted sleep, sleep/wake shifts, motion sickness, residual sedation from sleep medications).
Similar performance effects resulting from chronically restricted can also be seen in the Category I study by Belenky et al.[21] and in figure 3-3.
PVT testing showed severe impairments in reaction time under the 3-hour condition, with lapses in responses increasing steadily across the 7 days of sleep restriction.
Cognitive impairments are present even after an individual has been awake for approximately 17 hours; in fact, recent studies have shown that these decrements are similar to those that result from an elevated blood alcohol level.
[24] These findings are compelling as the duration of wakefulness (17 hours), which results in decrements that are similar to those that are induced by a 0.05% blood alcohol level, is considered by many to be within the range of a "normal" waking "day"; many individuals can recall an incident in which they had to waken early in the morning and work all day into the night.
It has long been recognized that a positive relationship exists between daily rhythms of the body temperature and neurobehavioral performance and alertness in humans.
Working overtime increased the odds of making at least one error, regardless of the originally scheduled length of the shift.
Analysis revealed a significant relationship between the number of extended-duration work shifts and the reported rates of fatigue-related noteworthy medical errors.
Evidence from this study further corroborates the negative impact that extended-duration work shifts may have on performance, as well as increased accidents and injuries.
[13][14] Working extended hours or overnight shifts also poses the added difficulty of requiring performance from an individual at a time with the body is driven to sleep by the circadian system.
Night workers are particularly prone to vehicle accidents, and their decreased alertness, performance, and vigilance are likely to blame for a higher rate of industrial accidents and quality control errors on the job, injuries and a general decline in work productivity rate.
[29][30][31][32] In summation, ground-based evidence demonstrates that sleep loss, circadian desynchronization, and extended work shifts lead to increased performance errors and accidents.
This article incorporates public domain material from Human Health and Performance Risks of Space Exploration Missions (PDF).
