Sleep, performance, circadian rhythms, and light-dark cycles during two space shuttle flights
Sleep, circadian rhythm, and neurobehavioral performance measures were obtained in five astronauts before, during, and after 16-day or 10-day space missions. In space, scheduled rest-activity cycles were 20-35 min shorter than 24 h. Light-dark cycles were highly variable on the flight deck, and daytime illuminances in other compartments of the spacecraft were very low (5.0-79.4 lx). In space, the amplitude of the body temperature rhythm was reduced and the circadian rhythm of urinary cortisol appeared misaligned relative to the imposed non-24-h sleep-wake schedule. Neurobehavioral performance decrements were observed. Sleep duration, assessed by questionnaires and actigraphy, was only approximately 6.5 h/day. Subjective sleep quality diminished. Polysomnography revealed more wakefulness and less slow-wave sleep during the final third of sleep episodes. Administration of melatonin (0.3 mg) on alternate nights did not improve sleep. After return to earth, rapid eye movement (REM) sleep was markedly increased. Crewmembers on these flights experienced circadian rhythm disturbances, sleep loss, decrements in neurobehavioral performance, and postflight changes in REM sleep.
Available from: Geoffrey Edward Jones
- "Other negative effects include increased levels of fatigue, depression, and confusion as well as decreased immunological function and concentration (Belenky et al., 1987; Giam, 1997; Naitoh and Kelly, 1992). Potential chronic health effects include increased risk of gastrointestinal illness , loss of bone mineral density, coronary artery disease, depression, some forms of cancer (Antunes et al., 2010; Dijk et al., 2001; Schernhammer et al., 2001), and alterations in metabolic profile, mood, and appetite (Arendt, 2010; Dijk et al., 2001; Scheer et al., 2009; Schernhammer et al., 2001). "
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ABSTRACT: United States Navy submariners have historically lived with circadian disruption while at sea due to 18-h-based watchschedules. Previous research demonstrated that circadian entrainment improved with 24-h-based watchschedules. Twenty-nine male crew members participated in the study, which took place on an actual submarine patrol. The crew were exposed, first, to experimental high correlated color temperature (CCT = 13,500 K) fluorescent light sources and then to standard-issue fluorescent light sources (CCT = 4100 K). A variety of outcome measures were employed to determine if higher levels of circadian-effective light during on-watch times would further promote behavioral alignment to 24-h-based watchschedules. The high CCT light source produced significantly higher circadian light exposures than the low CCT light source, which was associated with significantly greater 24-h behavioral alignment with work schedules using phasor analysis, greater levels of sleep efficiency measured with wrist actigraphy, lower levels of subjective sleepiness measured with the Karolinska Sleepiness Scale, and higher nighttime melatonin concentrations measured by morning urinary 6-sulfatoxymelatonin/creatinine ratios. Unlike these diverse outcome measures, performance scores were significantly worse under the high CCT light source than under the low CCT light source, due to practice effects. As hypothesized, with the exception of the performance scores, all of the data converge to suggest that high CCT light sources, combined with 24-h watchschedules, promote better behavioral alignment with work schedules and greater sleep quality on submarines. Since the order and the type of light sources were confounded in this field study, the results should only be considered as consistent with our theoretical understanding of how regular, 24-h light-dark exposures combined with high circadian light exposures can promote greater behavioral alignment with work schedules and with sleep.
Available from: Shawnda A Morrison
- "), or sometimes even unchanged (Frost et al. 1976). Studies on sleep during Space Shuttle Missions reported that astronauts had more wakefulness and less SWS in the third part of the night (Dijk et al. 2001) compared to other times during their sleep cycles. Unfortunately, due to methodological concerns, lack of objective measures, and a general paucity of data regarding sleep in space, it is not known whether sleep architecture would be affected over long-duration missions, including planetary habitation. "
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The objective was to determine the separate and combined effects of hypoxia and inactivity/unloading on sleep architecture during a 10-day period of confinement.
Ten subjects participated in three 10-day trials in random order: hypoxic ambulatory (HAMB), hypoxic bedrest (HBR), and normoxic bedrest (NBR). During the HAMB and HBR trials, subjects were confined to a hypoxic facility. The hypoxia profile was: simulated altitude of 2,990 m on day 1, 3,380 m on day 2, and 3,881 m on day 3. In the NBR and HBR trials, subjects maintained a horizontal position throughout the confinement period. During each trial, sleep polysomnography was conducted one night prior to (baseline; altitude of facility is 940 m) and on the first (NT1, altitude 2,990 m) and tenth (NT10, altitude 3,881 m) night of the 10-day intervention.
Average time in sleep stage 1 decreased from NT1 to NT10 irrespective of trial. Overall incidence and time spent in periodic breathing increased from NT1 to NT10 in both HAMB and HBR. During NT1, both HAMB and HBR reduced slow-wave sleep and increased light sleep, whereas NBR and HBR increased the number of awakenings/night. There were fewer awakenings during HAMB than NBR.
Acute exposure to both hypoxia and bedrest (HBR) results in greater sleep fragmentation due to more awakenings attributed to bedrest, and lighter sleep as a result of reduced slow wave sleep caused by the hypoxic environment.
Available from: Laura Sebastiani
- "typically observed in short-term space missions, due to circadian rhythm phase shifts, heightened workload demand, emergencies, and more in general, extraordinary stressful environmental conditions (Dijk et al., 2001; Mallis and DeRoshia, 2005). In this light, a crucial problem for long lasting manned missions in space is represented by sleep alterations. "
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ABSTRACT: Spaceflights "environment" negatively affects sleep and its functions. Among the different causes promoting sleep alterations, such as circadian rhythms disruption and microgravity, stress is of great interest also for earth-based sleep medicine. This study aims to evaluate the relationships between stress related to social/environmental confinement and sleep in six healthy volunteers involved in the simulation of human flight to Mars (MARS500). Volunteers were sealed in a spaceship simulator for 105days and studied at 5 specific time-points of the simulation period. Sleep EEG, urinary cortisol (24h preceding sleep EEG recording) and subjectively perceived stress levels were collected. Cognitive abilities and emotional state were evaluated before and after the simulation. Sleep EEG parameters in the time (latency, duration) and frequency (power and hemispheric lateralization) domains were evaluated. Neither cognitive and emotional functions alterations nor abnormal stress levels were found. Higher cortisol levels were associated to: i) decrease of sleep duration, increase of arousals, and shortening of REM latency; ii) reduction of delta power and enhancement of sigma and beta in NREM N3; iii) left lateralization of delta activity (NREM and REM) and right lateralization of beta activity (NREM). Stressful conditions, even with cortisol fluctuations in the normal range, alter sleep structure and sleep EEG spectral content, mirroring pathological conditions such as primary insomnia or insomnia associated to depression. Correlations between cortisol fluctuations and sleep changes suggest a covert risk for developing allostatic load, and thus the need to develop ad-hoc countermeasures for preventing sleep alterations in long lasting manned space missions.
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