Astronauts are losing decades of bone mass in space that many do not recover even after a year on Earth, researchers have found, warning that it could be a “major concern” for future missions to Mars.
Previous research has shown that astronauts lose between 1% and 2% of bone density for each month they spend in space, as the lack of gravity takes the pressure off their legs when it comes to stopping and walking. .
To find out how astronauts recover once their feet have returned to earth, a new study scanned the wrists and ankles of 17 astronauts before, during and after a stay on the International Space Station (ISS).
The bone density lost by astronauts was equivalent to the amount they would lose in several decades if they returned to Earth, said study co-author Dr. Steven Boyd of the University of Calgary in Canada and director of the McCaig Institute. for Bone and Joint Health.
The researchers found that the astronauts’ spinal cord density had not fully recovered after a year on Earth, and they were still missing a decade of bone mass.
The astronauts who did the longest missions, which lasted four to seven months on the ISS, were the slowest to recover. “The more time you spend in space, the more you lose,” Boyd said.
Boyd said it was a “big concern” for future planned missions to Mars, which could see astronauts spend years in space.
“Will it continue to get worse over time or not? We don’t know, “he said.
“We may get to a steady state after a while, or we may continue to lose bone. But I don’t imagine we’ll continue to lose it until there’s nothing left.”
A 2020 modeling study predicted that during a three-year space flight to Mars, 33% of astronauts would be at risk for osteoporosis.
Boyd said some answers could come from research currently underway on astronauts who spent at least a year aboard the ISS.
Guillemette Gauquelin-Koch, head of medical research at the French space agency CNES, said the weightlessness experienced in space is “the most drastic physical inactivity there is.”
“Even with two hours of exercise a day, it’s like you’re lying in bed the other 22 hours,” said the doctor, who was not part of the study. “It won’t be easy for the crew to set foot on Martian ground when they arrive; it’s very disabling.”
The new study, published in Scientific Reports, also showed how spaceflight alters the structure of the bones themselves.
Boyd said that if you think about the bones of a body like the Eiffel Tower, it would be as if some of the metal connecting rods that support the structure had been lost. “And when we get back to Earth, we thicken what’s left, but we don’t really create new bars,” he said.
According to the study, some exercises are better at retaining bone mass than others. Deadlifting was significantly more effective than running or cycling, he said, suggesting heavier lower body exercises in the future.
But the astronauts, who were mostly fit and in their 40s, did not realize the drastic bone loss, Boyd said, noting that the Earth’s equivalent, osteoporosis, is known as “the disease silent “.
Canadian astronaut Robert Thirsk, who has spent more time in space, said that for him, his bones and muscles took longer to recover after space flight.
“But a day after landing, I felt comfortable again as an earthling,” he said in a statement accompanying the investigation.