It's not easy to be an astronaut! The latest study confirms that space flight may cause permanent bone loss in 20 years

It's cool and proud to break out of the earth and enter space.

Currently, humans have been hoping and committed to exploring a second home outside the Earth. Perhaps in the distant future, humans may really be able to take the latest spacecraft, escape from the Earth, rush out of the solar system, and reach a new habitable home.

However, scientific research has confirmed that after the human body leaves the Earth's gravitational magnetic field, it will be affected by space microgravity, radiation, etc., and may even suffer irreversible damage.

Now, a new study has reaffirmed the dangers of space flight.

Leigh Gabel, a sports scientist at the University of Calgary in Canada, and his team and collaborators tracked 17 astronauts with an average age of 47 (who lived in space for 4-7 months) and found that during space missions lasting 6 months or longer, astronauts may experience permanent bone loss equivalent to 20 years of aging.

The related research paper, titled "Incomplete recovery of bone strength and trabecular microarchitecture at the distal tibia 1 year after return from long duration spaceflight", has been published in the scientific journal Scientific Reports.

Bring your dumbbells

Once humans leave the Earth's gravity and magnetic field, microgravity and radiation in space will become a big problem.

Long-term exposure to microgravity can cause astronauts' brains to swell, increase the amount of cerebrospinal fluid surrounding the brain and spinal cord, and even affect vision.

Similarly, in microgravity, muscles will not remain tight like they do on the ground. Just like a person who has lost the ability to move, the leg muscles will appear loose and slowly atrophy due to lack of exercise.

When two cosmonauts returned from a then-record 18-day space flight aboard Soyuz 9 in June 1970, one of them was so frail that he couldn't even carry his helmet when he stepped out of the landing capsule.

In addition, space radiation may also increase astronauts' risk of cancer and other diseases.

Ever since humans left the Earth and entered space, scientists have improved the design of spacecraft countless times and made space suits more comfortable to wear, but they still cannot protect astronauts' bodies from the harm of space.

Although weightless astronauts exercise for several hours every day in the space station to maintain their strength, other issues of life in microgravity remain unresolved.

Today, scientists are designing artificial gravity suits, radiation-resistant drugs and miniaturized medical tools that could be ready in about a decade to keep future space travelers safe and healthy.

In this work, the research team measured the astronauts' 3D bone microstructure at a scale of 61 microns (thinner than a human hair) by using high-resolution peripheral quantitative computed tomography (HR-pQCT), imaging the bone structure of the tibia in the lower leg and the radius of the forearm.

Image: Using high-resolution computed tomography imaging allows researchers to study 3D bone microarchitecture in astronauts’ skeletons (tibia example shown here). The subtle details can reveal changes in bone density and strength.

They recorded and calculated bone strength and density at four time points: before the astronauts' space flight, when the astronauts returned from space, and six months and one year after their return.

Data shows that astronauts who live in space for less than six months can restore their pre-spaceflight bone strength one year after returning to Earth.

Astronauts who spend a long time in space experience permanent bone loss in their tibiae, which is equivalent to decades of aging.

Once the microscopic tissue that provides the bones with overall strength is gone, it cannot be rebuilt even after the astronauts return to Earth, but the remaining bone tissue will thicken to a certain extent.

In this regard, Leigh Gabel, one of the authors of the paper and a sports scientist at the University of Calgary in Canada, said that bones are living organs. They are full of vitality and activity and are constantly remodeling, but without gravity, the bones will lose their strength.

Another finding was that the astronauts' forearm bone structure and radius barely changed, a possible reason being that forearm bones are not load-bearing bones.

In response to this phenomenon, Steven Boyd, a sports scientist at the University of Calgary, also suggested that "increasing weightlifting training in space can help reduce the problem of bone loss."

Figure｜Leg strength training helps reduce bone loss caused by microgravity environment.

Laurence Vico, a physiologist at the University of Saint-Etienne in France, believes that the possible extended space flight time in the future will cause astronauts to suffer more bone loss and greater recovery problems.

This is particularly worrying because even trips to Mars in future manned missions will last at least two years.

Photo: Scientists are studying how to protect astronauts on missions to Mars given the limited space available for medical equipment.

Additionally, Vico added, space agencies should consider other bone health measures, such as nutritional supplementation, to reduce bone resorption and increase bone formation.

In the future, Gabel, Boyd and their colleagues hope to gain insight into what happens to astronauts when they spend more than seven months in space. This research is part of an ongoing NASA project to study the effects of a year of spaceflight on more than a dozen body systems in astronauts.

"We really hope to find a 'plateau' where astronauts stop losing bone mass after a period of time," Boyd said.

Astronauts' efforts

It is really not easy to become an astronaut.

In addition to suffering from damage from microgravity and radiation in space, astronauts also have to undergo extremely cruel "devil" training on Earth.

For example, in order to withstand the huge overload, stay awake and operate correctly during the ascent and descent of the spacecraft, they will undergo overweight endurance and adaptability training and withstand 8 times the gravitational acceleration in a high-speed rotating centrifuge.

They will also perform vestibular function training, doing 360-degree clockwise and counterclockwise rapid movements, while swinging up and down and forward and backward. The main purpose is to improve the stability of vestibular function, reduce the incidence of space motion sickness, and alleviate the symptoms of space motion sickness.

Another item is neutral buoyancy tank training, in which astronauts conduct extravehicular activity training in a simulated weightlessness training environment, especially extravehicular operations such as extravehicular walking, extravehicular assembly and maintenance.

In short, every action completed in space is the result of several times more effort on Earth.

In addition, in order to ensure that astronauts can walk upright, it is also necessary to equip future space stations with some artificial gravity machines, such as the lower torso negative pressure system (LBNP).

When the astronaut's body is sealed from the waist down, the device applies vacuum pressure to the astronaut's lower body. The vacuum recreates the downward pull of gravity, allowing the astronaut's feet to stand firmly on the floor of the space station and draw body fluids toward the legs.

Figure｜LBNP

But these LBNPs are just early forms of artificial gravity, and their advantage is that they may be easier to send into space than the alternatives being tested.

As mentioned earlier, centrifuges can simulate gravity through centrifugal force, helping astronauts work better in microgravity environments.

However, how to bring such a bulky centrifuge into space is still a big problem.

But no matter what, I believe that with the advancement of science and technology, humans will have the ability to allow astronauts and even more people to leave the earth and live in space more comfortably.

References:

https://www.nature.com/articles/s41598-022-13461-1

https://www.sciencenews.org/article/astronauts-mars-space-health-survival