Articles in PresS. J Appl Physiol (February 4, 2016). doi:10.1152/japplphysiol.00928.2015
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Analogs of Microgravity: space Research without Leaving the Planet-Highlighted Topic (Mini Review)
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Effects of Isolation and Confinement on humans – Implications for manned space
explorations
Pagel JI1 and Choukèr A1
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Stress and Immunology Lab, Department of Anesthesiology, Hospital of the University of Munich,
Germany
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Alexander Choukèr, Prof. Dr.
Department of Anesthesiology
University of Munich
Marchioninistrasse 15
81377 Munich, Germany
E-Mail to contact authors:
[email protected];
[email protected]
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Number of Figures:
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Number of Tables:
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Number of text pages:
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Abstract:
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Running title: Isolation and confinement in space analogue research
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Copyright © 2016 by the American Physiological Society.
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Abstract:
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Human psychology and physiology are significantly altered by isolation and confinement. In light of
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planned exploration class interplanetary missions, the related adverse effects on the human body
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need to be explored and defined as they have a large impact on a mission’s success. Terrestrial space
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analogues offer an excellent controlled environment to study some of these stressors during a space
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mission in isolation without the complex environment of the International Space Station. Participants
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subjected to these space analogue conditions can encounter typical symptoms ranging from
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neurocognitive changes, fatigue, misaligned circadian rhythm, sleep disorders, altered stress
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hormone levels and immune modulatory changes. This review focuses on both the psychological and
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the physiological responses observed in participants of long-duration space-flight analogue studies,
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such as Mars500 or Antarctic winter-over. They provide important insight into similarities and
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differences encountered in each simulated setting. The identification of adverse effects from
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confinement allows not only the crew to better prepare for, but also to design feasible
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countermeasures that will help support space travelers during exploration class missions in the
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future.
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Key words: space analogue, stress, psychoneuroendocrinology, circadian rhythm, immunity
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Introduction
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In the evolution of mankind, gregarious behavior such as hunting or living together in small groups
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has been proven advantageous for survival. Sharing of specialized tasks and the division of labour
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into different professions catering to the individuals’ talents have enabled the development of
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multifaceted well-functioning modern societies. Isolation and exclusion from a social group as well as
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confinement have been forms of punishment since the early ages and continue to be the case in
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societies and prisons all over the world (9). Nevertheless, voluntary long-term confinement as a pair
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or with a group of people can cause strains on individuals. Differences in nationality, cultural
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background and character traits may induce severely altered stress levels and tension between the
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confined subjects, which can result in various disease states.
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Historic reports
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During the initial winter assignment of the US Amundsen-Scott Station at the South Pole in
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1956 under the framework of the International Geophysical Year (IGY), one of the team members
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developed a severe case of paranoid schizophrenia. This endangered the crew as well as the mission
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where he had to be sedated and confined for the rest of his stay (1, 53, 55). The arduous weather
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conditions in Antarctica and the awareness of long-term confinement with a group of mostly
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strangers can be quite challenging and stressful for the human mind (54). It is difficult to delineate
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what the exact trigger was for that episode. At the time no provisions had been made to treat such a
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patient and evacuation was impossible. Stuster wrote in his book “Bold endeavors” (53) that the
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patient was confined to a “special room lined with matresses (…) to contain the sounds of psychotic
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ravings”. The condition was clearly severe and long-term sedation was the only option the team had.
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Based on reports from Nardini et al 1962 (31), this unexpected incident has led to routine psychiatric
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screening as a part of the recruitment process for missions to Antarctica. What remains unknown, is
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whether the individual had predispositions for developing such an episode due to prior mental health
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or an entirely new manifestation. The individual did display abnormal behavior for a considerable
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time period prior to the manifestation of the psychotic episode with signs of disorientation and
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disruptive behavior. One could also speculate that he felt isolated because he did not “fit” into the
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team or that many different aspects of the situation reactivated a psychiatric condition he already
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had. What became clear though is that a 12-month stay in Antarctica can trigger an acute spell of
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psychosis, which makes psychiatric screening necessary. Such a screening is also applicable to the
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multifactorial environment of spaceflight, where the human body is subjected to many physiological
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and psychological stressors at the same time. Group tension and displacement of negative emotions
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can easily arise between crew members in orbit as well as between crew members and mission
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control personnel (23, 4). In this regard, the effects of extended stays in orbit and future
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interplanetary missions where personnel are subjected to long-term isolation and confinement are of
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great interest.
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Stress and stress prevention strategies
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Although well-established stress prevention techniques like autogenic training can be acquired prior
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to a mission, the participant’s ability to integrate and to interact with team members is key to the
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development of favorable group dynamics and vital to the successful outcome of such a mission.
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Stuster, who compared the characteristics of interplanetary missions to long-term naval expeditions,
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identified the character traits necessary for successful adaptation to isolation and confinement such
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as tolerance, emotional control or a sense of humor (52). As Selye stated in 1950: “Anything that
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causes stress endangers life, unless it is met by adequate adaptive responses.”(3) The individual’s
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genetically programmed and/or acquired adaptation mechanisms allow human beings to better cope
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with stressful situations. But when do neuro-humoral or metabolic stress response systems,
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specifically triggered by isolation and confinement, turn neuro-psychological strain into
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pathophysiological symptoms? What are the favorable genetically primed or behavioral coping
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strategies that provide some individuals with an advantage for overcoming such a situation? What
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kind of countermeasures can be set in place to help the crew of exploration class missions in coping
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with the adverse conditions? In other words, can confinement related stress be treated in a specific
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way? To answer these questions and to be able to design preventive measures, terrestrial space
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analogues offer the unique opportunity to study single aspects of space travel separately without the
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complex setting of actual spaceflight.
The analogues offer i) a standardized high fidelity experimental setting such as the
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experimental Mars500 mission simulation (in Moscow/Russia), or at the envihab facility
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(Cologne/Germany) and ii) “real expedition” conditions such as in Antarctica. In addition, some
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analogues allow simultaneous data collection from a larger number of subjects and the
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implementation of a broader spectrum of methods. This mini review will look exemplarily at the
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current data available from studies conducted in terrestrial space analogues with the focus on
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isolation and confinement, and describe the psychological and physiological reactions and symptoms
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observed in participants (see table 1).
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Laboratory based spaceflight simulations
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The 105 as well as the 520 day studies of the Mars500 programme, which was conducted jointly by
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Roscosmos, the European (ESA) and the Chinese Space Agencies, were conducted at the refurbished
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isolation facility located at the Institute of Biomedical Problems (IBMP) in Moscow, Russia. They
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investigated the effects of long-term confinement in a group of six volunteers during a spaceflight
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simulation to Mars. Although translation to a real Mars mission is limited (e.g. lack of microgravity or
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exposure to radiation), this form of space analogue research allows an undisturbed view of the
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effects of confinement on participants.
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2.1
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The facility was designed as a 550m3 habitat with four interconnected modules under artificial light
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(50-300lx) (61). As a pilot study, Mars105 was conducted prior to Mars520 from March 31st to July
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14th 2009. Mid-term isolation during Mars105 did not affect the participants’ overall health as much
The factor of duration
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as during longer confinement in Mars520, which involved 520 days of confinement from June 3rd
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2010 to November 4th 2011. There was no evidence of altered subjective psychological stress level,
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hypothalamic–pituitary–adrenocortical axis (HPA) (glucocorticoid, catecholamine levels) activity, or
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changed sleep patterns during Mars105 (16, 51). Autonomic heart rate variability (HRV) showed
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increased amplitude oscillations at all frequencies and a reduced mean heart rate during the daytime
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(increased wake parasympathetic activity) in contrast night time observations during sleep (61).
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Although no acute inflammation or elevated plasma cytokine levels were detected, distinct effectors
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of innate immunity were found to be inconsistently deregulated. Granulocyte mediated H2O2
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production and shedding of the cell adhesion molecule CD62L were both found to be increased in the
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volunteers (51). Many studies drew the conclusion that Mars105 did not impose a very strong stress
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stimulus on participants and the observed effects were therefore limited (16, 51). By contrast, when
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volunteers were confined for 520-days, the neuroendocrine stress responses were significantly
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altered. The responses of the endocannabinoid system were partly affected (67) and the level of
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salivary cortisol and catecholamines as markers for HPA activity were found to be increased during
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isolation (22, 63, 64, 67). Accordingly, a decrease in cortical activity of α- and ß-waves can be
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correlated with the sensory deprivation and monotony encountered during isolation (22). Physical
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activity decreased during isolation and resulted in impaired neuromuscular performance mainly in
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the lower limbs (7). Moreover, the circadian heart rate and HRV were significantly disrupted and
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circadian misalignment was observed due to the lack of natural daylight (62). A well-balanced
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day/night cycle, however, with adequate sleep/rest and activity phases properly synchronized to the
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circadian rhythm is critical for keeping the crew healthy (5, 6, 9). During long-term confinement, the
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percentage of sleep and rest phases increased, sleep quality and sleep-wake periodicity were
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disrupted resulting in a decreased performance of participants (5, 6), which was paralleled by
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reduced positive emotion ratings (67). The influence on the immune system includes a higher
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percentage of lymphocytes (∼ 50%), an increase of CD3+T cells with a stable ratio of CD4+ helper T
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cells/ CD8+ cytotoxic T cells and CD19+ B cells (64). IFN-γ and TNF-α secretion after stimulation with
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Epstein-Barr-Virus (EBV) antigen, a measure for adaptive immune response towards viral antigens,
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was altered (14, 64).
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2.2
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Certain crew members are more prone to suffer from disease or psychological strains than others.
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This can be due to distinct character traits, emotional instability or a genetic predisposition (36).
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Interestingly, some of the Mars520 participants showed stronger shifts in the sleep-wake cycle than
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others. Common genetic variations rendering individuals prone to sleep restriction and sleep cycle
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disruption have already been suggested. Their use as predictive biomarkers would help to identify
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vulnerable astronauts prior to a mission, where one can implement adequate countermeasures such
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as supported rhythm alignment with the use of an artificial external zeitgeber (19). Moreover, crew
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members with prior experience in spaceflight mission under difficult circumstances are beneficial in
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critical situations. An astronaut who stays on the ISS for the first time will find it more difficult to
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adjust to the conditions and will therefore have a different experience than someone who has been
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there before and the same is true for confinement in space analogues.
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2.3
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The Simulation of Flight of the International Crew on the Space Station (SFINCSS-99) isolation study
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was also conducted at the IBMP from July 1999 to April 2000. The first group consisted of four
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Russian males who were confined for 240 days in a 100m3 combined working and sleeping room. The
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second group comprised of 4 males and spent 110 days in a 200m3 area with separated dorms for
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every subject. It was shown, that acute psychic stress, as measured by a self-evaluation
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questionnaire, did not occur in participants neither during the 110-day nor during the 240-day
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confinement (7). The innate immune system, however, was consistently activated as measured by
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enhanced expression of ß2 integrins and elevated amounts of circulating granulocytes. Interestingly,
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the return from confinement back to normal surroundings exerted the strongest immunological
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changes in the subjects (7). This more pronounced effect on immunity might be due to the restricted
The effect of the individual crew member
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The effect of available free space
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free space availability for participants (200m3/100m3 versus 550m3 during the Mars studies). The
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restricted space allowed little chance to retreat from the group during tense and stressful situations.
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2.4
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Confinement simulation under such high fidelity conditions is not only a platform to test the effects
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of space flight during the mission, but also provides excellent conditions to investigate the effects of
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environmental re-exposition, such as the return to Earth, when landing on another planet or
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destination in space (65). Moreover, post-mission observation periods can include another
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evaluation of the physiological system and serve as an acute insult to the organism in testing for
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persisting effects of such prolonged confinement. 6 months after completion of their mission, the
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Mars520 volunteers were subjected to acute stress during a parabolic flight campaign to compare
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the stress burden of these previously confined subjects to healthy and unaffected volunteers. After
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the exposure to 30 parabolas with repeated 1 G, 1.8 G and 0G phases, salivary cortisol levels and
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urinary excretion of epinephrine were increased compared to pre-flight (63). Interestingly, in
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comparison to the control group, cortisol levels were much higher in the Mars520 group indicating
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that a chronic stress burden leads to a priming effect with pre-activated HPA.
Post-operational long-term effects
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Antarctica, a testbed for real exploration type isolation conditions
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Expeditions to reach Antarctica were a heroic endeavor in the 19th century that fascinated people
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and Roald Amundsen eventually reached the South Pole on 14 December 1911. Today, the extreme
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inhospitable environment has not lost its fascination and is host to international research facilities
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such as the French-Italian Concordia Station at Dome C located 3.233m above sea level on the
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Antarctica Plateau. Concordia is one of the inland all year research stations together with the Russian
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Vostok Station and the US Amundsen-Scott South Pole Station and is situated 1,100km inland from
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the coastal-based French research station Dumont D’Urville. Other research facilities situated at the
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coast include the German Neumayer- III and the British Halley IV research stations.
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3.1
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Pre-selection of suitable expedition volunteers, with regard to psychological and physiological health,
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is a difficult task (36, 54). Palinkas and Suedfeld defined three critical personal character traits for
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successful polar missions: task ability, emotional stability, and social compatibility (36). Although
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volunteers are thoroughly screened, a 5.2% incidence of DSM (Diagnostic and Statistical Manual of
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Mental Disorders) IV validated disorders were detected in participants after return with mood
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disorders being the most common diagnoses (30.2%), followed by adjustment disorders (27.9%),
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sleep-related disorders (20.9%), and substance-related disorders (9.3%) (33). The 1-year incidence
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values of DSM IV classified disorders in the general public of the USA evaluated in the National
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Epidemiologic Survey on Alcohol and Related Conditions (NESARC) were lower: major depressive
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disorder (1.51%), generalized anxiety disorder (1.12%), bipolar I disorder (0.53%) and drug
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dependence (0.32%). (20). Nevertheless, the results of the NESARC survey are evidently not directly
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comparable due to study design, group size and composition. Being encapsulated with the thought of
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“nowhere to go”, surrounded by a vast ice covered landscape and spending a winter with a 3-month
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lasting complete darkness put full year inhabitants under extreme psycho-social strain, which has
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been recognized already during the first winter-over crew in the 1950s (31, 53, 55). Psychological
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adaptation to this extreme setting is a multifactorial process (32). Typical symptoms that participants
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of polar expeditions report are fatigue, headaches, gastrointestinal problems, sleeping difficulties,
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impaired cognition such as a state of spontaneous fugue also called “the Antarctic stare” (35),
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depressed mood or tension towards crew members (21, 27, 30). The psychosocial effects of the
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Antarctic environment are noted to be of seasonal nature. The characteristic stare is accompanied
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with motionlessness and speechlessness, lasting 1 to 90 minutes, has been reported in the majority
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of winter–over crew members after the onset of winter and ended shortly before the return of
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daylight (37). Furthermore, this behavior correlates to reports of depression. Though this is not a
Psychological strain of an extreme environment
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proper classified condition according to the DSM IV, the combined state of sleeping disorder,
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cognition impairment, negative affect and tension towards crew members is referred to as the
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winter-over syndrome, which becomes aggravating in the second half of an expedition. This
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characteristic time-course is completely independent of the duration of the expedition and referred
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to as the third quarter phenomenon (34, 36). The polar triiodothyronine syndrome (T3 syndrome)
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comprises of subclinical seasonal changes of thyroid gland function including lower levels of the
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effector hormone T3 (hypothyroidism) and elevated levels of thyreotropin-stimulating hormone
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(TSH) (39, 41). These changes, though subclinical in nature, significantly correlate with cognitive
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performance and mood alterations as evidenced by the Profile Of Mood States (POMS) questionnaire
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(40). Changes in the HPA axis were also detected. Supplements of levothyroxine and exposure to
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bright light (10,000 lux) during winter had beneficial effects on the observed mood alterations
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(35,40). During the early adaptation phase (1 month) of the Concordia winter-over crew in 2008,
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cortisol levels and stress questionnaires did not report higher stress levels. However, 24h urinary
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catecholamine excretion was significantly increased (13).
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3.2
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The environmental conditions in spaceflight and the analogues can be described as hypobaric
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hypoxic. Therefore decreased mean oxygen saturation levels (85.7 and 88.7%, at 1 week and 1
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month, respectively) as well as elevated hemoglobin and platelet levels were detected. Plasma
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adenosine, a measure for hypoxia related immune alterations, was slightly increased at 1 week and
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accordingly, a leukocyte subpopulation shift towards granulocytes was detected alongside impaired
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PMNL activation and H2O2 production (13). Innate immune modulations at the mucosal barrier
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revealed seasonal changes in immunoglobulin (Ig) A and IgM levels, where maximal immune
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suppression inversely correlated with altered psycho-social stress at a time-point after 4 months (18).
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Unfortunately, acute stress symptoms or hormone levels were not investigated. In a different study,
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anti-inflammatory cytokines (IL-10 and IL-1RA) were found to be decreased whereas pro-
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inflammatory IFN-γ was elevated (44). The observed immune changes demonstrate a shift towards a
Environmental triggers of the immune system
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pro-inflammatory type 1 CD4+ T helper cell (TH1) dominant phenotype (45) and are in line with the
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previously observed EBV-viral reactivation study (29, 58). Interestingly, body weight supplementation
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of vitamin D has shown to reduce the shedding of EBV into saliva (47,69).
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3.3
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The decline of cognitive performance is one of the key issues during long-term spaceflight. Its decline
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during spaceflight due to monotony or increased sense of stress could lead to devastating outcomes.
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Frequently reported symptoms of cognition impairment include memory loss, difficulties
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concentrating, increased reaction time and disturbance of vigilance (30,40). The previously
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mentioned fugue states and even an increased susceptibility to suggestion belong to the canon of
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symptoms (3, 36). The dimension of cognitive impairment during Antarctic winter-over is yet to be
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elucidated. A couple of studies were unable to measure such a decline and this seems to depend on
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testing format, the composition of crew members and the course of the mission (1, 28,40). Abeln et
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al., for example, used commercially available games to test cognitive tasks such as visuoperceptual
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speed, reaction time, arithmetics and object recall. However, likely due to a training effect, no
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alterations in cognition were detectable (1). Other studies showed that the motivation of subject was
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key to good performance values (12). Due to inconsistent use of testing formats and variable subject
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composition as well as limited study size, it is difficult to compare study results and to detect discrete
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changes.
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3.4
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New research increasingly focuses on advanced imaging techniques to quantify neurocognitive
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alterations and the brain’s ability to quickly adapt to altered stimuli (neuroplasticity) in confined
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situations such as long-term spaceflight. Advanced magnet resonance imaging (MRI) techniques such
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as Diffusion Tensor imaging (DTI) (15) allow for the visualization of diffusion changes in target
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neurofiber tracts, which enables direct measurement of the distinct changes due to neuroplasticity
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(11). With the use of DTI and whole brain voxel-based analysis, it has been shown that patients
Impairment of cognition
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New strategies for the evaluation of neurocognitive performance
suffering from bipolar I disorder exhibit distinct white matter changes when compared to healthy
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controls (4). Studies using DTI in space and Antarctic winter-over crews are still ongoing (17, 26,60)
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and results of these studies are highly anticipated. Functional MRI (fMRI) comprises of MRI imaging
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and a simultaneous functional performance of the test subject. The person investigated is first
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examined in a resting state and then asked to mentally visualize activities (e.g. imagining running,
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walking etc.). Recently published data examining a single astronaut before and after a 6-months
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flight in space revealed alterations in vestibular and motor-related regions. The observed
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dysfunctions were clinically correlated with vestibular ataxia and reduced motor control abilities.
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Interestingly, these dysfunctions likely originate from the cortex, rather than from deconditioned
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gravity sensing organs as previously suggested (59). The application of these MRI methods will
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greatly advance our knowledge on the neurocognitive effects in terrestrial analogue and spaceflight
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studies. The immune modulatory changes together with the severe psychosocial stress render
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Antarctica as one of the most interesting space analogues available. Aside from all the predominant
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negative effects, it is worth mentioning that many volunteers return with positive memories of their
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expedition to Antarctica. A stay at Antarctica for a short time or for winter-over is for many a once in
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a lifetime challenge and adventure, not to mention a worthwhile undertaking.
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Short term confinement in underwater habitats: bridging science to operational
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needs
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Human beings can experience Isolation and confinement not only in prepared laboratory settings or
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specialized research facilities, they encounter it everyday. A naval expedition or sailing trip where
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one is confined to a vessel with others and exposed to the force of nature, very closely resembles an
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interplanetary mission (53). The vastness of the ocean does provide some sensory input (daylight,
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animals, colors) but when diving, these sensory inputs are eradicated. Saturation divers live and work
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in underwater-pressurized habitats. The nature of this remote and extreme environment makes
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underwater habitats an excellent facility for space analogue research. The Aquarius Reef Base is an
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underwater sea laboratory currently owned by the Florida International University (FIU) and located
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in the Florida Keys National Marine Sanctuary at an operating depth of 47 feet and operating
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pressure of 2.5 Atos. NASA Extreme Environment Mission Operations (NEEMO) trains astronauts in
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this unique underwater setting during 10 -14 space analogue missions. Astronauts are subjected to
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isolation and confinement in an extreme environment based station, daily 5-9 hour dives simulating
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extra vehicular activity (EVA), and circadian-rhythm misalignment due to a lack of natural
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synchronizers (10,50).
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In a pilot study investigating 6 male astronauts in the context of innate immune alterations
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before, during and after hyperbaric hyperoxia, no psychoneuroendocrine changes were detected.
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Blood analysis revealed leukocytosis, granulocytosis, monocytosis and lymphocytopenia during the
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dive. Whereas pro-inflammatory cytokines such as IL-2, IL-6, IL-8, TNF-α and IFN-γ remain
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unchanged. An increased expression of the adhesion molecule CD11b and shedding of CD62L on
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PMNLs were also detected. Moreover, PMNL related H2O2 production exhibited an increased
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sensitivity to adenosine (50). These results illustrate an inflammatory high alert state with increased
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sensitivity towards possible stimuli. Similar systemic proinflammatory states and increased oxidative
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stress were also observed after a short dive (56). Well known inflammatory markers of red blood cell
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metabolism, the total body iron stores (serum ferritin) (46) and toxic labile iron forms (non-
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transferrin-bound iron), were increased in the participants (2, 8). Blood homocysteine levels went up
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while the activity of superoxide dismutase (SOD) deteriorated , suggesting oxidative stress during the
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dive (68).
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Though NEEMO is a very special setting with hyperbaric hyperoxic conditions, it shows that
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even a 14-day exposure to such a harsh environment can cause changes in immunity and antioxidant
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levels in the body. The long-term effects remain unknown, since a prolonged observation was not a
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part of the protocol. Clearly as human beings, we are not adapted to these living conditions but these
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would be the conditions on other planets such as Mars. Even if we were to build an artificial habitat
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with tolerable atmospheric conditions, we have to be aware of the fact that our body will still react
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to the non-Earth environments. Correspondingly, our immune system will most likely encounter
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altered and more virulent strains of Earth pathogens or perhaps completely novel foreign pathogens
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in space. This means astronauts are faced with adverse conditions with an impaired immune
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response, making medical support and optimizations all the more important in space flight.
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5
Analogue environment for future space exploration
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The evolution of human kind is still ongoing. On our journey to another planet we would have to rely
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on the sharing of responsibilities among crew members similar to the early ages when we
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transformed from hunter-gatherers into ancient civilized societies. The extensive program of
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cosmonaut and astronaut training allows these candidates to experience some aspects of space
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travel in a relatively secure setting on Earth. Evidently, an intensive and exhaustive training for
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astronauts is crucial for the success of a mission but can only be as good as the scientific foundations
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it is based on. Program designers and scientists have to define what risks and dangers astronauts
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might encounter and to better prepare them: future manned exploration to the moon, asteroids and
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to Mars can be best practiced when the facilities appropriately simulate outer space conditions. This
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will become increasingly more critical since the Earth bound analogues will be a function of the
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mission scopes, mission length and overall boundary/budgetary estimates of such future exploration
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class missions. The selection of an analogue mission scenario must meet two criteria: it must be a
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high fidelity simulation which enables in-depth exploration of space flight related stressors on a large
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number of subjects and be representative of the missions anticipated in the next 10-25 years. In the
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post ISS era, several vehicles and missions are in the planning and pre-planning stages, ranging from
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free flyers in various Earth (or even lunar) orbits or beyond. These projects include the Chinese Space
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Station CSS, “landing”-docking scenarios on asteroids, expeditions to the moon or with prolonged
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presence as a stepping stone for future Mars missions. The aim is for these plans to be realized by
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2050. These conditions and scopes are highly variable, the analogues must address the effects of
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various group sizes, gender composition, limited living space in the spacecraft vs. more spacious
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habitats at the lunar or planetary destination. Also, the effect of life support systems (regeneration,
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green houses) must be considered alongside the effects of the atmospheres. The latter is generally
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speaking a hypobaric and hypoxic condition to facilitate extra-habitat/vehicular activities, but
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imposes fire hazards and technical constraints (57).
363
Depending on the scopes and in particular, the confinement facilities , high fidelity mid- to long-term
364
simulations with variable crew sizes of three and more crew members can be accommodated, for
365
example, in Russia. The Human Exploration Research Analog (HERA) facility and NEEMO, will support
366
research especially on operational issues, crew composition and day to day life in habitats. When
367
environmental or additional life support systems are to be tested with measurements on human
368
organ homeostasis, the newly built and recently operational envihab facility (25) or the Olympic sport
369
center in Planica (48) are favorable candidates. When a non-artificial habitat is to be tested,
370
Antarctica seems to serve as the most hostile and mission relevant environment at either hypoxic
371
(e.g. the French/Italian Concordia-, the US Amundsen–Scott South Pole- or the Russian Vostok-
372
Station), or normoxic conditions (e.g. at the British Halley VI or Neumayer III).
373
Already to date, given the broad portfolio of space analogues available for research, scientists have
374
been gathering data from very unique and interesting environmental settings on Earth. But each and
375
every analogue has its own characteristics, which has been described in this review (See table 2).
376
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353
377
6
Space analogues as training facilities
379
Analogue studies provide valuable insight for two parties, on the one hand to the scientific
380
community by extending our knowledge in the field, on the other hand to Cosmonauts and
381
Astronauts as they gain experience while taking part in mission simulations. As such, complete
382
mission simulations are highly valuable tools. The ESA CAVES program (Cooperative Adventure for
383
Valuing and Exercising human behavior and performance Skills) is a training opportunity where
384
astronauts participate in a cave exploration with the goal of encountering new life forms and to train
385
teamworking skills (49). The nature of the strange and uncommon environments inhabited by often
386
novel organisms surviving off of elements like manganese or sulfur, without light and in a potentially
387
life threatening setting offers a training scenario for space missions (8, 49). Similarly to the effects
388
observed during the Mars confinement studies, the reunion with daylight after leaving the darkness
389
and seclusion of the cave is a highly emotional experience for participants. With regard to an
390
expedition to Mars, extraterrestrial caves are being discussed as a possible first natural form of
391
habitat on Mars (8). Expanding this approach of priming the crew to space like conditions and
392
especially to prolonged confinement and isolation, a “mission” to Antarctica before Mars can
393
certainly be worthwhile preparation.
394
395
7
Coping strategies and countermeasures in space analogues
396
Current strategies to ameliorate the effects of isolation and confinement in space or Antarctica
397
involve first and foremost the careful selection of candidates for group compatibility, social skills as
398
well as psychological and physical health (31). Once mission bound, maintenance of crew health is a
399
better strategy than therapy. Providing good nutrition and dietary supplements can prevent disease.
400
This could involve previously mentioned levothyroxine (35) or Vitamin D (69) supplements.
401
Furthermore, physical exercise was found to be beneficial for a balanced mood in Antarctica (1) and
16
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378
402
during Mars500 (42). Sleeping disorders and disruption of the circadian cycle can be reduced at least
403
in part with the use of an artificial zeitgeber e.g. 10,000 lux bright white light (35). Core social coping
404
strategies involve team building exercises, team activities or entertainment and access to
405
communication such as “support from home”. Current research stations in Antarctica are capable of
406
providing access to the Internet or telephone. Social bonding between fellow crew members
407
especially for long-term confinement missions is best achieved prior to the mission, if possible.
408
Training in space analogue facilities can be a platform to achieve this goal.
409
8
Conclusion and outlook
411
Isolation and confinement can put the human body under a large amount of psycho-neuro-endocrine
412
duress, which results in measurable pathophysiologic symptoms. Terrestrial space analogues offer a
413
very good setting for scientists to study these effects and to provide international space agencies
414
with the information they need to select, prepare and to protect astronauts in short spaceflight and
415
in particular, long-term exploration class missions. Experiments in analogue environments offer
416
unique conditions to explore the nature of human adaptation and to allow high fidelity investigations
417
in a clinical context. As such, standardized conditions of confinement (e.g. MARS500, envihab,
418
PlanHab and other in the US and in China) can be advantageous in their application as a metabolic
419
chamber for nutritional and metabolic studies (38, 66) or as a hypoxic environment for disease
420
studies in human organs.
421
Despite the scientific advancements thus far, exploration class interplanetary missions are a
422
bold endeavor not for the faint of heart. They require not only brave and experienced crew members
423
but also a huge amount of resources including further technical developments, medical scientific
424
research and strong psychological support. These investments into further investigations will not
425
only be required for safe manned space exploration but will no doubt serve to benefit life on Earth.
426
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410
427
428
Acknowledgements: The authors are very grateful to the support from Anne Guo (MD, Department
429
of Anaesthesiology, Munich, Germany) for language editing of this manuscript. The authors are
430
supported by grants (Nr 50WB0919, 50WB1317) from the German Ministry of Technology and
431
Energy (BMWi) as handled by DLR.
432
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18
9
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no psychoneuroendocrine
effects observed
Psychological
Effects
Mars520 study
• high inter-individual differences in the behavioral
responses
• symptoms of depression
• reduced positive emotion ratings
Antarctica (Concordia)
• cognitive impairment
• mood alterations (depression)
• tension towards crew members
• sleeping disorder
• state of spontaneous fugue
• third quarter phenomenon
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Mars105 study
• signs of sensory deprivation and monotony
(decrease in α and ß waves)
• heart rate and HRV significantly disrupted
• sleep quality and sleep-wake periodicity
• impaired neuromuscular performancecircadian
heart rate and HRV significantly disrupted
• salivary cortisol and urinary catecholamine
secretion increased, the endocannabinoid 2arachidonoylglycerol (2-AG) decreased
• lymphocytosis with an increase of CD3+T cells
• IFN-γ and TNF-α secretion after stimulation with
Epstein-Barr-Virus (EBV) antigen were altered
• post-mission parabolic flight campaign: salivary
cortisol levels and urinary excretion of epinephrine
were increased compared to preflight and unlike
the control group
• pro-inflammatory type 1 CD4+ T helper
cell (TH1) pronounced phenotype
• impaired PMNL activation and reduced
capacity to produce H2O2
• EBV-viral reactivation
• polar T3 syndrome
• elevated 24h urinary catecholamine
excretion
• elevated hemoglobin and platelets
• elevated Plasma adenosine
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Physiological
effects
• increased HRV
• increased wake
parasympathetic activity
• inconsistent immune
changes
• increased shedding of the
cell adhesion molecule
CD62L
• Granulocyte mediated
H2O2 production elevated
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no major psychoneuroendocrine
effects observed
NEEMO
• leukocytosis
• granulocytosis
• monocytosis
• lymphocytopenia
• inflammatory alert state
• increased total body iron stores
• increased oxidative stress
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