Rosemary S. A. Shinkai, DDS, MSc, PhD
Professor of Dentistry, Pontifical Catholic University of Rio Grande do Sul, Brazil
We still do not know much about the changes in dental and orofacial structures, functions, and diseases beyond Earth. Early studies on aerospace dentistry published at the end of the 1960’s and 1970’s addressed some concerns about oral health in astronauts and challenges for dental treatment delivery in space. If astronauts are selected for being the most prepared and healthy humans to withstand the hard conditions in outer space, what about everyday regular people, the very young or old individuals? Or pregnant space voyagers? Microgravity and radiation in long-term spaceflights and a lifelong stay in space stations or settlements would require specific oral health care.
Teeth, gums, tongue, bones, and muscles are part of a complex system, which is highly innervated and irrigated by blood vessels to allow chewing, swallowing, speaking, and smiling. Saliva is produced by a number of large and small salivary glands to lubricate the mouth, form the food bolus, and counterbalance acids produced by mouth bacteria after meals. Recent studies have shown that the microgravity and spaceflight environment alters jaw bone physiology, dental development, saliva proteins, and salivary gland morphology in mice flown on a US shuttle and a Russian biosatellite. Another study revealed that adult rats submitted to gravity tests showed remodeling of craniomandibular bones. Simulated microgravity also modified gene expression and physiology of Streptoccocus mutans and Streptoccocus sanguinis, possibly altering the cariogenic potential of these bacteria. However, the specific effect of space radiation also needs to be investigated.
It still is unknown to what extent the same effect would occur in human astronauts. Besides the potential structural and physiological changes in the craniomandibular system, other behavioral factors and epigenetics are involved in space oral health. For example, dental caries result from a frequent exposure to acids produced by mouth bacteria after ingestion of sugar, mainly sticky or soft, paste-like foods. Thus, eating and cleaning habits modify the risk for dental caries. And the protective saliva flow and composition vary with water drinking, chewing stimulation, medication, and stress. All these factors may be altered in space life and would affect individual responses to not only dental caries risk, but also gum inflammation, orofacial pain, bone loss and repair. Understanding the underlying mechanisms to prevent oral health problems and have effective interventions seems to be appropriate for the planning of long-term space travel.
So, space dentistry may be an interesting job in the future!
Prof. K. Ganapathy
InnovaSpace Advisory Board member, Past President Telemedicine Society of India, Former Secretary/Past President Neurological Society of India & Indian Society for Stereotactic & Functional Neurosurgery, Emeritus Professor Tamilnadu Dr MGR Medical University, Former Adjunct Professor IIT Madras & Anna University Madras, Founder Director, Apollo Telemedicine Networking Foundation & Apollo Tele Health.
Three decades ago even contemplating the subject of the human brain in space would have been considered preposterous. Two decades hence and Extra Terrestrial Neurosciences could become a distinct sub-speciality. With periods of stay in the International Space Station steadily increasing, manned missions to the Moon being revived, and even humans going to Mars being seriously planned, it is imperative we know what happens structurally and functionally to various parts of the human brain when it is exposed to microgravity and cosmic radiation for prolonged periods. This is no longer a theoretical academic discussion. For decades we have relied on experimental simulation studies on the brains of rats exposed to microgravity and cosmic radiation. Mice exposed for six months to the radiation levels prevalent in interplanetary space exhibited serious memory and learning impairments, also becoming more anxious and fearful. Structural changes at a microscopic level, including changes in neurotransmitters were demonstrated.
It is only in the last decade that reliable, prospective clinical and sophisticated imaging studies have been carried out on astronaut brains before and after exposure to real world conditions. The human brain was primarily designed for standing in gravity on Earth with almost no exposure to radiation. When we leave the Earth’s gravitational pull all bodily fluids move upward. The first evidence for structural changes in the brain after long-term spaceflight includes narrowing of the central sulcus, a shrinking of the cerebrospinal fluid (CSF) spaces at the vertex, and an upward shift of the brain. MRI scans before spaceflight, shortly after and several months after return to Earth revealed a significant increase in size of the lateral and third ventricles immediately post-flight and a trend towards normalization at follow-up. There was an upward shift of the brain after all long-duration flights. Significant volumetric gray matter decreases, including large areas in the temporal and frontal poles and around the orbits have been documented. This effect was more noticeable in crewmembers with prolonged stay in the International Space Station. Bilateral focal gray matter increases within the medial primary somatosensory and motor cortex (cerebral areas representing lower limbs) were noted. Cortical reorganization in an astronaut’s brain after long-duration spaceflight has now been confirmed.
MRI documented structural changes raise the risk of possible impairment of behaviour, cognition and performance. This could compromise mission critical decisions. In 2017, a study revealed that long missions in space results in reduction of protective CSF surrounding brain volume at the top of astronauts’ brains. These changes underlie the astronauts’ performance on certain critical tasks, such as opening the space station’s hatch, climbing a ladder, exiting a vehicle or even walking along the surface of a planet. Follow up MRI scans have revealed that re-exposure to Earth’s gravity and lack of continuing exposure to unnatural radiation can generally reverse these space travel induced changes. Astronauts have to undergo extensive training before and during spaceflight to maintain muscle mass, and this can result in localised increased grey matter, particularly in the sensorimotor regions of the brain, representing the lower limbs. This is due to neuroplasticity or adaptation within the cerebrum and cerebellum.
The most notable findings in the MRI’s were a post-flight increase in the stimulation-specific connectivity of the right posterior supra marginal gyrus with the rest of the brain; a strengthening of connections between the left and right insulae, decreased connectivity of the vestibular nuclei, right inferior parietal cortex and cerebellum with areas associated with motor, visual, vestibular, and proprioception functions. Study of permanent visual acuity impairments associated with spaceflight have demonstrated structural changes in the CSF around the optic nerves and the globe of the eyes.
Domain expertise in Extra Terrestrial Neurosciences will eventually be a reality. While the number of subjects studied may at the best be a few hundreds, the lessons learnt could make us relook at the traditional neurosciences we have been believing in for the last two centuries.
Let us never forget that the future is always ahead of schedule !!
Nelson A. Campos Vinagre
Commercial pilot / Professor of Sports Science
Sporting activities for athletes with disability have existed for more than a 100 years. Relevant contributions to this area of knowledge occurred in the 18th and 19th centuries that demonstrated the importance of sports participation in the rehabilitation and re-education process of people with special needs. Cutting-edge research has targeted methods that can reduce the consequences of living with reduced mobility and, at the same time, provide new ideas and possibilities for engaging in sporting activities as a means of treatment and rehabilitation. This has led in recent decades to greater opportunities for people with disabilities to participate in sports, and the prospect of further moves for inclusion in the coming years should continue to help improve their quality of life.
The mobility provided by assistive technologies is known to contribute positively to the medical and psychological needs and treatment of casualties of armed conflict and has provided them with opportunities to overcome the life-changing injuries they have endured, both the physical and mental challenges. The Invictus Games, championed by Prince Harry, Duke of Sussex, which first took place in London UK in 2014, is an excellent example of how the power of sporting inclusion can inspire wounded and sick service personnel in their rehabilitation, providing an arena to not only motivate them in their personal journeys to recovery but also to generate a wider understanding and respect from the general public for those who serve their country.
Equally, the showcase events of the Summer and Winter Paralympics, through being linked and following on from the traditional Olympic games for non-handicapped athletes, fosters greater equality for the disabled, putting them on the same global platform and helping change the way disability is perceived. More than 4,400 athletes with disability are expected to compete in the Summer Paralympics to be held in Tokyo in August 2020. The rising number of people with disabilities, covering all age groups, is made more evident through witnessing the larger numbers of these individuals taking part in physical and sporting activities. Their participation in sports as a means of improving health, quality of life and social interaction is an area of interest that I have followed over the many years of my career and it gave direction to my PhD research.
My doctoral thesis intended to improve understanding of the process of evaluating people with physical incapacities in the same way as people considered non-handicapped. It involved submitting the German athletes from the Paralympic Alpine Skiing Team to a standard physiological test on a treadmill and to an evaluation process performed in a wind tunnel, a device normally used to test aerodynamic profiles. It was a fascinating project as the relationship between the needs of those people being studied and the evaluation instrument used was not obvious, but we aimed to better observe broader and more accurate responses related to the physical and aerodynamics performance of the skiers involved, which it is hoped can benefit not only the ski team members, but also non-athletes who may or may not practice this sport.
The biomechanical aspects related to posture, motor learning and motor development of people with disability were also considered, as they may perform sports as a way of preventing major health risk implications or may desire to practice sports as a rehabilitative process to improve motor skills.
The motivation behind my thesis was also based on the possibility of conducting research that allowed the use and unification of different areas of expertise. The physiological investigation of disabled athletes, combining with testing them with aerodynamic loads in a wind tunnel could bring advances related to quality of life and the specific training and health of people with disabilities. A further important motivating factor was the idea of promoting the social inclusion of people with special needs through the organisation and interpretation of the scientific information obtained in this research, and applying the findings to scenarios of daily life and not just for elite athletes.
The efforts towards inclusion of individuals with special needs are helped with the advances in assistive technologies, such as exoskeletons to help people stand and walk, and numerous smartphone apps to help the visually impaired and deaf. Many countries have legislated to ensure that discrimination due to disability is avoided in the employment market. Therefore, with talk of ‘hotels’ in space and craft similar to the proposed Lunar Orbital Platform (Gateway) in the near future, should people with disability be considered for space travel and work where they are not pinned down by gravity? In fact, the answer is another question – why not? Stephen Hawking experienced microgravity during a parabolic flight, and seemed to safely enjoy floating in the air. However, studies are needed to respond to questions like these, but if they are never asked, they will never be answered.
MSc Space Physiology & Health; Human Performance Intern, McLaren Applied Technologies
With international space agencies and the real-life Tony Stark (Elon Musk) making huge advances in rocket technology, it is likely that within the next couple of decades humankind will touch down on Mars. However, this is only half the battle. The gravity on Mars is roughly one third as strong as Earth’s. You may be thinking “great, everything will require less effort”, and you’d be right, however, there is a huge caveat to that. As we’ve found from the results of time spent in space (the longest continuous period being 14.4 months), when people are exposed to levels of gravity lower than that on Earth, losses in muscle and bone occur; predominantly, in muscles which we continually use to walk and maintain our posture. You may have heard the expression ‘use it or lose it’ - hugely applicable here. These losses can increase astronauts’ risk of injury when returning to Earth by leaving them very weak and fragile. A return mission to Mars will take around 3 YEARS to complete, mainly because of the wait for the two planets to be close enough in proximity again to allow a relatively short journey home. That’s around 12 months in microgravity and around 26 months in Martian gravity. Now, it doesn’t take a rocket scientist to figure out that, based on the numbers, the outlook for muscle retention isn’t great. That being said, we‘re still pretty uninformed about the extent to which living on Mars will stimulate our muscles.
Recently, my colleagues and I conducted an investigation to try to shed some light on the matter. To do this properly, we needed to achieve two key things: 1) simulate walking in Mars gravity, 2) measure the activity in the muscles used for walking. With this, we compared the muscle activity produced while walking on Mars to that produced when walking on Earth, gauging the degree of muscle loss that we might expect for a mission to Mars and to inform countermeasures.
To simulate Mars gravity, we used a technique called lower body positive pressure (LBPP). There are a few different ways in which you can simulate partial gravity environments, but this one has fewer limitations than the rest. LBPP involves putting someone inside an air-tight inflatable box from the waist down. Through manipulation of the air pressure within, it can generate a lifting force, changing the weight of the person inside. Our device was designed and built by engineers at the John Ernsting Aerospace Physiology Laboratory at the Pontificia Universidade do Rio Grande do Sul (PUCRS) in Porto Alegre, Brazil. With a treadmill placed underneath, the participant could then walk in simulated Mars gravity. To measure the amount of activity inside the leg muscles, we then attached electrodes to the skin at each of the muscles we were interested in (a method called electromyography) which picked up an electrical signal that muscles give off when they are being worked. The more intense the signal, the more active that muscle is while walking.
What we found was quite unexpected. The results of our investigation suggested that there was no significant difference between the muscle activity observed while walking in Mars gravity and the muscle activity observed walking on Earth. If this were to be true, then it would not be foolish to think that we could use the 26 months on the Martian surface to reverse losses in muscle and bone suffered on the outward journey in preparation for the return trip. However, there were two important variables that we failed to account for in our experiment. These variables were stride length and stride frequency when walking.
The moon is smaller than Mars, and so there is even less gravity there, but the same principle applies. With this in mind, even if the results of our experiment were to be true and the walking muscles are getting just as much activity with each step on Mars as they are on Earth, theoretically, they will be used less often. Considering our ‘use it or lose it’ principle, this would still mean muscle and bone loss to a disabling degree in the absence of effective counter strategies; which are currently lacking. More studies need to be done around this area, accounting for all variables, to further our understanding of human performance on Mars and ensure the safety of our astronauts, or we’ll be keeping Elon Musk waiting at the launch pad!