Astronaut Health Studies to Enable Space Exploration

Scientists led by University of Calgary have researched bone loss in astronauts. An important question is whether bone loss can be reversed after returning to Earth.

"Bone loss happens in humans - as we age, get injured, or any scenario where we can't move the body, we lose bone," says researcher Leigh Gabel in a press release issued by University of Calgary. "Understanding what happens to astronauts and how they recover is incredibly rare. It lets us look at the processes happening in the body in such a short time frame. We would have to follow someone for decades on Earth to see the same amount of bone loss.”

Bone loss happens in space because bones that would normally be weight-bearing on Earth, like leg bones, don't have to carry weight in microgravity. Like other astronaut health issues, bone loss depends on the individual. And there are different responses.

Their study is now published in Scientific Reports. It has followed 17 astronauts before and after spaceflight over the last seven years to understand whether bone recovers after long-duration spaceflight.

Some astronauts have trouble walking due to weakness and lack of balance after returning from spaceflight, explains lead researcher Steven Boyd. But others are immediately able to ride a bike. Some astronauts who flew on shorter missions, under six months, recovered bone strength and density in the lower body better than those who flew for longer durations.

Weight-bearing bones only partially recovered in most astronauts one year after spaceflight. This suggests, explains Gabel, that “the permanent bone loss due to spaceflight is about the same as a decade worth of age-related bone loss on Earth."

Astronaut Robert Thirsk, former Chancellor of University of Calgary, has direct personal experience. "Just as the body must adapt to spaceflight at the start of a mission, it must also readapt back to Earth's gravity field at the end," he says. "Fatigue, light-headedness, and imbalance were immediate challenges for me on my return. Bones and muscles take the longest to recover following spaceflight. But within a day of landing, I felt comfortable again as an Earthling."

Others haven’t been so lucky. But I think we should consider bone and muscle loss, and other adverse health effects of human spaceflight, as important problems to be solved. Living and working in space affects the human body in ways that must be better understood to enable long term space exploration and expansion, which is important for the future of humanity.

"Astronauts will venture to deep space this decade and, in the coming centuries, humanity will populate other star systems,” is the powerful conclusion offered by Thirsk. “Let's push back the frontiers of space exploration now to make this vision possible."