Space & Health News – Sleep as Critical Health Factor in Space Exploration

The World Sleep Day is held the Friday before the spring equinox of each year, and this year that happened to fall on March 15th. There is no record of astronauts on the International Space Station celebrating the day through more sleep – though presumably they did, since the ISS Daily Summary Report informs us the crew was off-duty that particular Friday. The prior day, March 14th, had been rather exciting, as the 58S Soyuz had delivered cosmonaut Aleksey Ovchinin and astronauts Nick Hague and Christina Koch to the ISS and to a busy schedule which included a safety briefing and an emergency procedures practice session.

All in a day’s work for the ISS crew, who routinely pack multiple technical and scientific experiments, hardware maintenance and repairs, environmental measuring, medical tests, and video recordings during their workday – in addition to the mandatory 2 hours of physical exercise. Little wonder that sleep deprivation and fatigue are common complaints among astronauts! A study published in 2014 on the sleep deficiency levels in astronauts on space shuttle and ISS missions found that average sleep time was of just six hours – way short of the 8.5 hours of sleep recommended in their daily schedules.

As we’ve all learned from Arianna Huffington’s The Sleep Revolution and from other publications on the topic of sleep, insufficient and poor quality slumber can lead to a host of health and cognitive issues. Sleep deprivation affects several major body systems – the central nervous system (memory, thinking abilities and balance), the immune system (fending off infections), the digestive system (insulin production), the cardiovascular system (blood pressure regulation) and the endocrine system (hormone production) – and in extreme cases it can even lead to death.

WELCOME TO SPACE & HEALTH NEWS, our monthly briefing of opportunities and advances in deep space medicine and space health care. This issue of the Space & Health News looks at the progress made by the industry in studying the effects of sleep on astronaut performance and in improving astronauts’ sleep quality as a driver of good health.


Lighting Effects Studies: Spaceflight on the ISS exposes crew members to about 16 sunsets per day – a dizzying number for normal human beings – as the space station circles Earth once every 90 minutes. The frequent change from darkness to light severely disrupts the body’s natural circadian rhythm, which is pegged to the familiar 24-hour day/night cycle. Studies done on ISS crew members have found that, once the visual and light-intensity related terrestrial cues are gone, astronauts’ bodies lose track of time and physiological parameters related to the circadian rhythm, such as body temperature and cortisol, decrease or fall behind by as much as 19% of the time during the spaceflight.

To counter both circadian misalignment and on-the-job sleepiness, in 2016 NASA initiated the Lighting Effects Study to test the light’s properties as a natural stimulant that can improve alertness and performance. The old fluorescent light bulbs on the ISS were replaced with solid-state light-emitting diodes (LEDs) with adjustable intensity and color – the so-called Solid-State Light Assemblies (SSLAs) – which emit light at different frequencies based on a lighting schedule that follows the human circadian cycle.  Thus, a higher-intensity blue-light-enriched light setting is used when elevated alertness or circadian adaptation is required, while the blue-depleted white light setting aids in falling asleep.

If you wonder how the human body perceive the changes in light color and intensity – the study’s principal co-investigators Dr. Steven Lockley (Brigham and Women’s Hospital) and Dr. George Brainard (Thomas Jefferson University) have the explanation ready: “The human eye contains a light-sensitive protein called melanopsin, different from the rods and cones that we use to see, which detects light in the eye and mediates these effect. Melanopsin is most sensitive to short-wavelength blue light and so by increasing or decreasing the proportion of these blue wavelengths in white light, we can enhance alertness, or promote sleep, respectively.”

Crew members’ duration of activities and sleep, plus the level of ambient light they experience, are monitored by the Philips Actiwatch Spectrum wristband devices astronauts wear, and the data collected from the sleep logs is subsequently compared to the crew members’ subjective assessment of the amount and quality of their sleep and alertness.

Analog Studies on Human Sleep: Due to the high costs and logistical difficulties of performing experiments in space, NASA, in cooperation with partner organizations from Russia, Germany, France, Italy and other countries, conducts field tests in locations that have physical similarities to the extreme conditions encountered in space environments. Such studies are called “analogs” as they produce physical, mental and emotional effects on the human body similar to those experienced in space. Ground-based analog studies play a significant role in spaceflight research as they save time, money, equipment and personnel, and allow for countermeasures to be tested on Earth prior to trying them out in space.

The Concordia Research Station, one of the three all-year research stations in Antarctica, was selected as the site of a 13-month long human sleep and performance study conducted by researchers from several universities in Belgium, in conjunction with the European Space Agency (ESA). The study took place during the harsh Antarctic winter season, which starts in March and ends in October. During wintertime, local temperatures can drop below −80 °C (−112 °F) – making Concordia Station one of the coldest places on Earth, and a reasonable “analog” for living in outer space.  

The research team used polysomnography – a sleep study procedure conducted using special equipment that records brain waves, oxygen levels in the blood, heart rate, breathing rate, and eye and leg movements – together with psychomotor performance testing and self-reported sleepiness and fatigue, to measure the effects of extreme environmental conditions on human sleep and performance.

All the study participants were recorded displayed high-altitude periodic breathing – alternating periods of deep breathing and shallow breathing, which was not surprising given the station’s elevation of 3,233 m (10,607 ft). Delays in falling asleep, fatigue, and fragmented sleep patterns were also observed, and were attributed both to self-selected bedtimes as well as to the extreme light conditions due to the long polar night.

The study found that participants’ individual responses to the extreme environmental challenges showed large differences and but remained relatively stable throughout the duration of the study, suggesting trait-like characteristics for these variables. This research has applicability for the astronaut selection process, as polysomnographic testing could be used to identify and select individuals with more robust sleep-resilience characteristics.


“Space Pillow System”: The design of the International Space Station (ISS) is eminently utilitarian. Catering to the basic needs of crew on relatively short-duration missions and limited by the volume-space available and the facility-building costs in space, the NASA and European astronauts’ crew quarters located in Node 2 of the ISS, the poetically-named Harmony module, are anything but cozy. Despite its name, this module is heavily trafficked as it serves as a connector and passageway between the U.S. laboratory, the European laboratory (Columbus), the Japanese laboratory (Kibo), the Pressurized Mating Adaptor 2 (PMA-2) docking area, and the berthing port for cargo vehicles. In Node 2, the crew quarters compete for space with the utilities equipment vital to the operation of the connected elements – the conversion and distribution of the electrical power, heating, cooling resources from the ISS Integrated Truss, and support of the data and video exchange with the ground and the rest of the ISS. One can’t help but wonder – how well can astronauts sleep in these conditions?

Enter Dr. Tibor S. Balint, Principal Human Centered Designer at NASA’s Jet Propulsion Laboratory, and Dr. Chang Hee Lee, Tutor in Innovation Design Engineering (IDE) Programme at the Royal College of Art (RCA), who believe that future space habitats must be designed taking higher-level human needs into account, and that the method best-suited to understand these needs is Human-Centered Design (HCD). Using HCD techniques, Dr. Balint and Dr. Change Hee Lee set out to create an artifact that provides an emotional connection between the space travelers and their terrestrial home – and they settled on the humble pillow. However, the “pillow system” they designed – which looks much like the current foam pad attached to the wall in an astronaut’s sleep pod – is a smart-pillow containing sensors that can detect when the astronaut falls asleep and automatically adjust lights in the sleep pod. The pillow is designed to be connected to a network of other objects in the astronaut’s living quarters – relaxing light displays, music speakers, aromatic devices, thermostat devices – and use AI algorithms to send inputs to these devices based on the astronaut’s movements during sleep.

Before you get too excited – keep in mind that this marvelous pillow exists currently only in Dr. Balint’s and Dr. Change Hee Lee’s futuristic drawings. Don’t lose heart though! Given the popularity of NASA’s Technology Transfer Program which makes innovations developed for space exploration available to the public, sensor-enabled “space pillow systems” might be in stores (and in space!) in just a few short years.


Robotic Friends: Companionship is a basic human need, and when this need is not fulfilled it can cause emotional and physical problems. Nowhere is this fact more poignant than in the far reaches of outer space, where astronauts spend long periods of time in isolation, away from family and friends and the comforts of home.

As a first step in addressing this issue, back in 2012 the Japanese scientists developed a humanoid robot designed to converse with astronauts and keep them company aboard the International Space Station. The robot’s creators, led by designer Tomotaka Takahashi, wanted the robot to “help solve social problems through communication”. “The main objective is that humans can talk to [the robot] and feel some sort of closeness to it,” the developers said.

The result of their efforts was Kirobo, the humanoid robot modeled on Astro Boy, who joined Japanese astronaut and ISS commander Koichi Wakata as a friendly robotic companion for an 18-month sojourn. Kirobo sported facial recognition software and language processing technology (from Toyota), was capable of responding to human questions without any pre-programmed responses, and was active on Twitter (!). The experiment was a success, but in an interesting reversal of roles, commander Koichi Wakata returned to Earth before his robot companion, leaving Kirobo stranded on the ISS and feeling, well, alone.

Fast-forward to today. Building on the growing interest in robotic companionship for astronauts, another Japanese designer – therapeutic tool creator Takanori Shibata – believes that equipping astronauts with cute-and-cuddly robotic stuffed animals like PARO, the baby seal, can help alleviate the stress astronauts experience during their stay in space, and maybe even help them sleep better. PARO is an autonomous robot, with sensors for vision (light intensity), audition, posture, touch and temperature. Its AI software allows PARO to learn and to distinguish between good stimuli and bad stimuli. If its owner gives it a new name and calls it again and again, PARO eventually learns the name and starts reacting to it. Being stroked is good while being hit is bad – these are innate values built into the robot’s AI software. As a result, PARO does his best to get its owner to stroke him and learns behaviors that its owner likes through direct interaction.

Just like a real pet, a robotic pet like PARO can produce actual physiologic changes in the human body, including lowering blood pressure and heart rates, and reducing muscle stiffness. Cortisol (the stress hormone) declines and oxytocin (the social bonding hormone) is released, which helps relieve feelings of stress and isolation and enhance the human owners’ communication and connection. With so much goodness built in, who wouldn’t want to go to sleep hugging a cuddly baby-seal robot?


Funding for Wearables Study: In June this year, Translational Research Institute for Space Health (TRISH) has approved funding for two research studies that use Philips’ Deep Sleep Headband technology to test how auditory stimulation protocols can be optimized to improve sleep and performance in space. During the night, our bodies cycle through different stages of sleep: rapid-eye movement (REM), and non-REM sleep, which has three stages. In the third stage of non-REM sleep, our heartbeat and breathing slow to their lowest levels and muscles relax. This is the most restorative stage of sleep often called “slow wave sleep”. The Deep Sleep Headband – already available on the market – works by detecting when the user enters the “slow wave sleep”. At that point, the headband’s algorithm triggers quiet audio tones to boost these slow waves, thus improving quality of sleep. Read more about these two studies here.

Funding for Sleep Research: The Sleep Research Society maintains a list of links to the federal and commercial organizations that provide funding for sleep research and studies. We can’t guarantee it is kept up-to-date, but it provides companies interested in pursuing this line of research with a great starting point. Click here to access it.


TRISH’s Red Risk School – a virtual, interactive workshop focused on NASA’s high-priority risks for human health during space exploratory missions – hosted a seminar on June 6-7, 2019 on the topic of “Behavioral Health and Sleep”. The presenter, Dr. David Dinges, Professor of Psychiatry at the Perelman School of Medicine, University of Pennsylvania, described in detail the interacting stressors affecting behavior and cognitive health in space.

As Dr. David Dinges explains: “The circadian rhythms, the approximately 24-hour rhythms that are in every cell of the human body – lymph nodes, circulation, liver, adrenals, kidneys, the brain – there’s a whole biological clock that regulates when we sleep and wake, our alertness levels, our performance levels, etc. Our physiology is manifested in these biological rhythms. When we go for long space travel, if we don’t maintain the psychological entrainment as though we’re still on a 24-hour schedule in a way that helps us maintain that coordinated biology, we can have a real problem. So the question is, what do we need to do to maintain our circadian rhythms when we’re in another location?”

The recorded session can be accessed here.


To Hibernate or Not to Hibernate: In 1999, Anna Bågenholm, a trainee doctor at the time, was skiing with two of her colleagues when she lost control during a steep descent and fell onto a layer of ice covering a mountain stream. The ice sheet broke under her weight and she was dragged underwater. Trapped under ice for 80 minutes before rescue services were able to retrieve her, her heart stopped beating and she stopped breathing, while her body temperature dropped to an unbelievable 56.7 °F (13.7 °C). By all accounts, she was dead.

Fortunately for Anna, the doctors at the University Hospital of North Norway in Tromso, where she was brought after her rescue, had experience in treating victims of accidental hypothermia. By bringing her core temperature up gradually, they were able to get her heart restarted four and a half hours later. It took Anna Bågenholm 12 more days to open her eyes, and many more months in intensive care and in physical therapy to recover. No permanent brain damage was diagnosed in her, despite the severe physical trauma.

The paradox of Anna’s survival lies in the fact that the same factor that could have killed her – the extremely low underwater temperature – was also what saved her. According to clinical research published by the Massachusetts General Hospital’s Proto magazine, Anna’s rapidly dropping body temperature slowed her metabolism down to ten percent of her baseline rate, to a point where she barely needed any oxygen at all, and where therefore the cardiac and pulmonary arrests she suffered were not fatal.

This paradox is nowhere more evident than in the aerospace community’s push and pull relationship with investing in research into medically induced hypothermia as a method for placing long-term space travelers into a state of metabolic stasis (or torpor) similar to animal hibernation.

Yuri Griko, a Moscow-trained NASA radiobiologist and lead senior scientist in NASA Ames’ space biosciences division, has spent years researching ways to protect astronauts from space radiation. What he found out was that metabolic stasis could be an effective countermeasure to cellular radiation damage. Animals in hibernation can survive radiation without significant cell-damage thanks to the much reduced oxygen consumption. Lower oxygen consumption means lower production of oxygen free radicals and lower oxidative activity at the cellular level – which extends cell life and counters the damage caused by ionizing radiation.  Griko’s studies also showed that hibernating animals lose less muscle mass than humans confined to bed rest for a similar length of time, and, also unlike humans, suffer minor to no bone loss during their rest period.

Despite these promising findings, Griko was not able to obtain funding for flight experiments involving hibernating animals – the next step in studying the effects of long-term medically-induced torpor in humans.

Another recipient of NASA funding for hibernation studies, SpaceWorks Enterprises, Inc., used the NASA Innovative Advanced Concepts (NIAC) grants received in 2013 and subsequently in 2016 to design travel habitat for small crews (four to eight crew members), who would be kept in torpor for the entire duration of the journey to Mars. SpaceWorks’ advanced designs included closed-loop oxygen and water production systems, medical devices for inducing hypothermia, and robots to check the crew’s body health indicators and perform maintenance tasks such as chemical feeds, biological waste disposal and muscular stimulation via electrical stimuli. SpaceWorks ultimately scaled up the habitat’s design to accommodate 100-passenger “settlement class” Mars missions with rotating torpor schedules for subsets of the crew.

Will NASA continue to fund these types of projects? Concerns about real-life applicability and the unforeseen deleterious effects of induced torpor on the human body have put a damper on NASA’s appetite for further investigations, for now.  But, as NASA’s and other space agencies’ plans for sending humans to Mars take shape and the deadlines start drawing nearer, the significant resource efficiencies coupled with potential health benefits offered by induced torpor will ensure that the topic does not get forgotten.

Further Reading: For an in-depth yet very approachable report on torpor and metabolic rate reduction in humans, the Hibernating astronauts—science or fiction? study conducted by a group of German researchers working with the European Space Agency (ESA) makes a convincing case that induced torpor will ultimately be the game-changer in long-distance space travel.

Note to our readers: We have changed the title of our monthly newsletter to “Space & Health News” (notice the ampersand), to reflect our trademarked site name and to distinguish it from other publications.

Featured photo, courtesy of NASA.

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