Sleep in Extreme Environment

Fig. 58.1
Effects of microgravity on fluid redistribution of upper trunk and face in the first few days in space (From the Internet domain of website)


  • 2.

    Low back pain due to osteoporosis associated with mineral (calcium) loss;


  • 3.

    The absence of body pressure associated with “floating” feeling in the spacecraft;


  • 4.

    Lack of sufficient motor activity reducing sleep quality;


  • 5.

    Discomfort from the space suits; and


  • 6.

    Space motion sickness in the first two days of mission (characterized by malaise, drowsiness, and illusion of position and motion) [23, 29] can be a problem compounded by the effects of medication used to treat it (e.g., intramuscular promethazine) causing drowsiness, alteration of alertness, and sleep loss.



    1. ii.



        The background noise within a spacecraft may reduce sleep quality. This noise may be produced by fans and other life support system, pumps, electrical engines, and frequent communications with ground mission control.

        1. iii.

          Psychological Factors

        Excitement of spaceflight, fear of death, or fear of life-threatening failure of the mission, stress and demand for mission work, unfamiliar environment, monotony and feeling of confinement within a closed space, and prolonged isolation causing visual and auditory hallucinations all of which can cause considerable sleep disruption.

        1. iv.

          Sleeping Medication

        This is used by about 50 % of astronauts as a short-term solution which may have a negative effect on performance.

        1. v.

          Circadian Dysrhthmia

        It has clearly been demonstrated that there are circadian rhythm changes during spaceflight (i.e., mismatch between the body’s internal clock and the geophysical environment as a result of rapid oscillations during light–dark cycles). While orbiting the Earth, the astronauts experience 90-minute light–dark cycle (i.e., 16 sunsets per day) disrupting the body’s intrinsic circadian rhythm.

        1. vi.

          Space Environment

        Excessively low temperature and occasional excessively high cabin temperature as well as excessive environmental light disturb sleep quality. There are other environment factors identified as contributing to sleep loss (e.g., spacecraft vibration, cosmic radiation, increased CO2 levels).

        1. vii.

          Sleeping Condition and Posture

        Confinement to sleeping bags, sleeping vertically and small crowded space inside spacecraft are not conducive to sleep (Fig. 58.2).


        Fig. 58.2
        Sleeping positions of four crew members of the STS-112 on the middeck of the space shuttle Atlantis (From the Internet domain of website)

        1. viii.

          Post-Flight Fatigue

        The cause of this is not known, but most likely results from severely compromised post-flight adaptation to gravity for several days after returning to the Earth after an extended space mission and cumulative sleep loss in space [19].

        1. ix.

          Miscellaneous Other Factors

          1. a.

            Thinning of the muscle mass from inactivity (not using to overcome gravity).


          2. b.

            Obscuration of vision and other eyesight problems (e.g., cataract) are noted after long space mission in men. Many astronauts also experience sudden phosphenes or light flashes [30] often noted before sleep with a sense of motion. It was noted in 47 out of 59 respondents in a survey, and some thought that light flashes disturbed their sleep.


          3. c.

            Cosmic radiation effect. It is not known whether there is a cosmic radiation effect in space mission posing as a risk factor for the development of cancer in the future.


          4. d.

            Some astronauts are more sensitive to sleep loss in space than on Earth. This susceptibility is dependent on individual characteristics (e.g., circadian chronotype, gender, and genetic susceptibility), which must be considered in pathophysiological mechanism and in designing individual treatment strategy.



        Countermeasures and Therapy

        Several lines of treatment and countermeasures have been suggested and tried to treat sleep disruption in space and its adverse effects, but further research is needed to optimize sleep and performance in spaceflight missions.

        1. i.


        Strenuous exercise as a countermeasure to prevent muscle atrophy and cardiovascular deconditioning was employed on Soviet spaceflights in the past [6, 31]. However, strenuous exercise can have adverse effects on sleep and mood [32]. On the other hand, timely performed exercise has shown to induce phase shifts in the melatonin circadian rhythm [6, 33, 34]: Phase advances were induced by late afternoon or early evening exercise, whereas late evening exercise induced phase delays. Timed exposure to exercise sessions could be used as countermeasures to facilitate adaptation of circadian rhythms in space missions [6, 33, 35].

        1. ii.

          An understanding of circadian physiology is essential to treat circadian dysrhythmia of the astronauts. Effective countermeasures to promote sleep in space include [1, 5, 6, 8, 13, 3638] modifications of sleep–wake schedule including scheduled naps, strategically timed exposure of bright light of specific wavelength, intensity, color and duration, intermittently or continuously as well as behavioral strategies including sleep hygiene measures. Another suggested strategy [38, 39] is to replace the adult monophasic sleep pattern by polyphasic patterns of childhood (ultrashort sleep schedule) which has shown to decrease total sleep requirement without impairing performance levels.


        2. iii.

          A comprehensive management approach should include education about sleep, sleep–wake schedule, following a common sense sleep hygiene measures as well as scheduling policies and procedures, and employment of specific fatigue countermeasures, and remedies including fatigue training workshops [40, 41].


        3. iv.

          Pharmacologic strategy using melatonin (0.3 mg) [13] and sleeping medications [1, 8] to improve sleep duration and shorten sleep latency has not been very effective. Intramuscular phenothiazine has been successfully used to treat space motion sickness [6], but may cause drowsiness and impaired performance in space crews.


        4. v.

          Other measures to improve sleep and performance in space mission crews include use of earplugs to minimize noise, window shades in space ships to protect crews from exposure to bright light, use of sleep-restraint bags attached to the wall (Fig. 58.2) in any position (vertical or horizontal) [1, 42], psychological services to the astronauts and their families, and mental monitoring to minimize external stressors.


        5. vi.

          The other suggestion for improving sleep, fatigue, and performance skill is acquisition of a strong coping mechanism to handle extreme environment—which shows considerable individual variation. This requires the development of high physiological, psychological, and social coping skills [1, 43].


        Sleep at High Attitude

        Climbing to high altitude (e.g., mountaineers at about 3000 meters above the sea level) exposes human to extreme environmental condition as a result of low barometric pressure associated with hypoxemia (hypobaric hypoxia) causing profound physiological changes in the body [1, 3]. The adverse consequences include periodic breathing and altered sleep–wake rhythms depending on individual susceptibility, speed of ascent, and the actual altitude reached. Those with pre-existing obstructive sleep apnea (OSA) show exacerbation of sleep-related breathing events. Altitude-related illnesses that have major impact on sleep include acute mountain sickness, chronic mountain sickness (Monge’s disease), as well as high-altitude pulmonary and cerebral edema [3]. Gradual ascent to altitude promoting acclimatization as a preventive measure and pharmacotherapy for sleep disturbances have been found to be useful in several clinical studies. The readers are referred to Chap. 33 for further details.

        Sleep in the Polar Regions

        Studies are very limited to make a firm conclusion about sleep and its disorders in the polar regions. Most of these came from Josephine Arendt and her group [4451] as well as from Buguet and his group [5254], and Palinkas and co-investigators [55, 56] (these authors mainly dealt with psychological–psychiatric aspects and sleep). A symposium in 1973 gave comprehensive overview of Polar Human Biology published as proceedings [57].

        1. i.

          It is extremely cold in the polar regions (Arctic 60°N and above; Antarctic 60°S and below), and people are deprived of natural sunlight in winter but have continuous daylight in the summer (“the midnight sun”) months (October to March in the Antarctic and April to September in the Arctic). There is no permanent human population at 60°s in Antarctica, which does not belong to any country, and has no government. There is a transient sparse population of scientists and researchers at several scientific bases (about 1000 population in winter and up to 4000 in summer). On the other hand, permanent human population north of 60° N in the Arctic amounts to over four million including indigenous people (“The Inuit”). The arctic region is governed by several nations—USA (Alaska), Russia (Siberia), Canada, Denmark (Greenland), Iceland, Norway, Sweden, and Finland.


        2. ii.

          There are reports of sleep problems in the polar regions. Because of deprivation of natural sunlight in winter, there is a delay in circadian rhythm in the evening, including melatonin rhythm with delayed sleep onset, decrements in SE, sleep duration, and quality associated with fatigue and tiredness in the morning [4450]. A few people desynchronize with free-running rhythm showing their intrinsic circadian period longer than 24 h. Timed exposure of light (blue-enriched light appears to be more effective than standard white light) on awakening in the morning combined with exogenous melatonin intake in the evening plus wearing sunglasses in the evening helps restore normal phase and sleep.


        3. iii.

          Palinkas and co-investigators [55, 56, 58] reported on psychological and psychiatric problems associated with sleep disturbance as a result of long periods of isolation and confinement in the polar regions. A small percentage of people on polar expeditions suffer from mood and sleep disorders [55, 58]. These authors examined sleep (self-reported) and mood measured by profile of mood states (POMS) in 91 American men and women who spent the 1991 Austral (refers to Southern Hemisphere) Winter (March to October) at three different research stations in Antarctica [56]. They made the observation that mood changes were preceded by changes in sleep characteristics.


        4. iv.

          Sleep in the polar regions was documented objectively by PSG study in the early 1970s in small and limited studies, but more comprehensive PSG evaluations were made later by Buguet et al. [53, 54] and other investigators [59]. PSG recordings [53, 54] in subjects sleeping in unheated tents in sleeping bags showed that SWS was preserved in the first half of the night as in neutral condition. There were numerous awakenings due to midnight hypothermia (rectal temperature = 34.9 °C). Thermoregulatory shivering and body movements disappeared during REM sleep. REM sleep episodes were shorter in the cold compared with thermoneutral condition resulting in REM sleep deprivation. In a later PSG study of eight individual, Buguet et al. [52] concluded that they could not draw a statistical conclusion as sleep patterns between individuals showed considerable variation.

          Bhattacharyya et al. [59] performed PSG study in six members of the Indian expedition team during their winter stay at Maitri, the permanent research station of Indian Antarctica (70°S). PSG findings included reduced sleep duration, SE, and SWS during the winter months. This study showed a prevailing general trend of sleep disturbance among overwintering members in a modern Antarctic station.


        5. v.

          Joern et al. [60] studied long-term sleep patterns in summer campaigners in South Pole Station (90° south and at 2804-m altitude) by PSG recordings which showed a loss of SWS in all subjects and REM sleep in the oldest subject (50 years old) which was thought to be related to altitude [1]. Long-term sleep patterns were also studied by PSG recordings in four Antartic winterers at South Pole Station (temperature of −78 °C) [61]. In Antarctica, sleep duration was same, but sleep latency was longer than in the USA and SWS decreased, and even disappeared, and REM sleep decreased during the winter. These changes were thought to be due to altitude. Similar findings (decreased SWS and REM sleep) were also noted at the Halley Station (built by the British Antarctic Survey in 1955) in 10 winterers for 38 nights using an Oxford Holter System [62]. SWS and REM sleep increased in summer, and the changes were most likely related to daylight variations.

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      1. Oct 7, 2017 | Posted by in NEUROLOGY | Comments Off on Sleep in Extreme Environment

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