Human Health and Performance Risks of Space Exploration Missions
Chapter 3
The behavioral consequences of performance errors due to sleep loss, circadian desynchronization, extended work shifts, fatigue, and work overload on ISS are currently being evaluated. Cognitive decrements that are caused by fatigue, inadequate light exposure, circadian dynamics, and work-sleep schedules, will more profoundly affect crews who are on a long-term lunar or Mars mission, where fewer resources will be available to mitigate these factors. The risk factors may become compounded by the fact that lunar and Mars missions bring additional restrictions. For example, returning to Earth from a lunar mission is not a readily available option, and returning to Earth during a Mars mission is not an option at all.
Currently, NASA STD-3001, Vol. 1 provides standards regarding a normal, uninterrupted sleep period; standards for circadian shifting caused by schedule demands; and limits for the amount of work that can be performed within 1 day and 1 week. The current standards, however, do not provide specific limits for performance thresholds. BHP anticipates developing normative databases for space flight using tools and measures that have been initially tested and verified in laboratories and high-fidelity analogs such as NEEMO [NASA Extreme Environment Mission Operations] and, subsequently, space flight. In mission analogs, astronauts can establish individual and group baselines as well as normative data for an environment that can be compared with space flight.
Flight designers and flight surgeons are concerned that crew members, and especially ground control personnel, may not be obtaining the minimum recommended rest periods: actual work-sleep time is not the same as the time that is planned. Evidence shows that, overall, sleep is shorter and interrupted in flight. During critical mission phases, schedule shifting and workload demands are strenuous for both ground and flight teams. It is important to ensure that the current NASA STD-3001, Vol. 1 standards are enforced to protect work-rest schedules for both ground and flight crews, particularly during high-tempo operations. If crews are shifted or have to perform during this allotted sleep time, recovery time needs to be allowed and individualized countermeasures need to be readily available.
Ground evidence clearly demonstrates the risk of performance errors due to sleep loss, fatigue, circadian desynchronization, and work overload. Reviews in the aviation and medical industry have consistently attributed accidents, injuries, and even death to performance errors arising from sleep and circadian issues. Furthermore, long-term health consequences serve as another potential outcome. The WHO International Agency for Research on Cancer Monograph Working Group recently concluded that, on the basis of published evidence, "shift work that involves circadian rhythm disruption is probably carcinogenic to humans" (Straif et al., 2007).
Space flight evidence shows that astronauts are regularly subject to shifting their sleep/wake schedules, long work hours, complex tasks, and sleep loss. The ground teams that support flight crews and robotic missions endure similar issues. As NASA transitions from LEO to lunar and Mars missions, flight and ground crews will certainly continue to face the challenges that are associated with acquiring adequate sleep, circadian desynchronization, fatigue, extended work shifts, and workload demands.
As space flight performance data are limited, BHP research aims to further characterize performance in the space flight environment using validated tools that detect cognitive deficits that are related to fatigue. Evaluations of gross motor performance in space flight are also anticipated. BHP research efforts will further describe the nature of sleep in space over long-duration missions, and tasks are under way to determine which factors en-
Risk of Performance Errors Due to Sleep Loss, Circadian Desynchronization, Fatigue, and Work Overload
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