Astronauts lose a lot of bone mass during space missions and they don’t easily regain it | Science

Scientists have been researching the bone density of astronauts for some time now. After all, during their stay in space there is no gravity, so there is no pressure on the body and the astronauts float around for a long time instead of walking. Previous research has shown that an average of 1 to 2 percent bone density – the amount of bone mineral in bone tissue – is lost per month an astronaut spends in space.

As we age, bone density decreases anyway. As a result, our bones become more brittle and break faster. For astronauts, that process is accelerated during their extraterrestrial journeys. The bone density they lose during a stay on the International Space Station (ISS) is comparable to the effect of decades of age.

Nine of the seventeen astronauts who took part in the study also found that bone density did not (completely) recover once they were back on Earth. “The longer you spend in space, the more bone you lose for good,” said Steven Boyd (Canada’s University of Calgary), director of the McCaig Institute for Bone and Joint Health.

Boyd says he is very concerned about future missions to Mars, which would require astronauts to spend years in space. “We don’t know if it will get worse over time or not,” Boyd said. “Maybe the loss stabilizes after a while, or we continue to lose bone density. I can’t imagine astronauts continuing to lose bone density until there’s nothing left.”

The findings of Boyd and his team are already in line with a model study that was carried out in 2020. It already showed that 33 percent of astronauts are at risk of osteoporosis, a chronic condition in which the bones are more brittle.