Astronauts Suffer Permanent Bone Loss Due to Lack of Gravity in Space, Sparks Concern for Long Missions

A new study from a team of researchers at the University of Calgary led by biomedical engineer Steven Boyd reveals that spaceflight of more than three months could cause permanent bone loss in astronauts even a year after returning to Earth. Researchers warn that it could be a big concern for future space missions.

Previous research showed that astronauts lose about one to two percent of bone density every month they stay in space because of the lack of gravity that takes the pressure off their legs when they stand up or walk.

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Astronauts Suffer Permanent Bone Loss Due to Spaceflight, A Big Concern For Future Space Missions

TBone Study: Prolonged Weightlessness Accelerates Bone Loss in Astronauts

Researchers from the Cumming School of Medicine at the University of Calgary followed 17 astronauts before and after their spaceflight for their study. They traveled to Johnson Space Center in Houston to scan the wrists and ankles of astronauts before they went to space and then scan them again after six months and one year since they arrived.

The research titled "Incomplete Recovery of Bone Strength and Trabecular Microarchitecture at the Distal Tibia 1 Year After Return From Long-Duration Spaceflight," published in Scientific Reports, is also known as the TBone study that lasted for seven years starting from 2015 to 2022, wherein they found that prolonged weightlessness accelerated bone loss in astronauts.

The study suggests permanent bone loss is possible among astronauts and only recovers partially even after a year in space. The bone loss is equivalent to age-related bone loss on Earth and is the result when bones do not have to carry weight in a zero-gravity environment, unlike here on Earth, CBC News reported.

Dr. Steven Boyd, director of the McCaig Institute for Bone and Joint Health, said astronauts usually had trouble walking due to weakness and lack of balance after months in space.

The findings reveal that those who stayed for less than six months recover bone strength and density in their lower body, but not so much for those who flew for longer missions.

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A Big Concern for Future Missions to Mars

Boyd pointed out that the study suggests a big concern for planned missions to Mars, which could send astronauts to the Red Planet and stay there for many years.

"Will it continue to get worse over time or not? We don't know," Science Alert quoted Boyd. "It's possible we hit a steady state after a while, or it's possible that we continue to lose bone. But I can't imagine that we'd continue to lose it until there's nothing left."

A 2020 study modeled a prediction of what a three-year spaceflight to Mars could look like. It shows that about 33% of astronauts are at risk of osteoporosis. That is why scientists study astronauts who have carried out space missions for at least a year onboard the International Space Station (ISS).

France's CNES space agency head of medicine research Guillemette Gauquelin-Koch explained that the weightlessness in space is the most drastic physical inactivity because exercising for two hours a day is also equivalent to being bedridden for the other 22 hours. Therefore, this adds to the challenge of humans setting foot on Martian soil when they arrive.