Floating in Space Might Seem Exciting, but It Has Serious Consequences

Although floating in space could be enjoyable, a TBone study reveals that it is taxing on earthly bodies.

According to a new study, six months in space is equivalent to decades of bone loss on Earth.

Have you ever wondered whether you have anything in common with an astronaut? It turns out that there are 206 of them – your bones. A study on bone loss in astronauts and the crucial issue of whether bone can be regained after returning to Earth focuses on these parts of our bodies.

Dr. Steven Boyd, Ph.D., director of the McCaig Institute for Bone and Joint Health and professor at the Cumming School of Medicine, launched the TBone study in 2015. In order to determine if bone recovers after “long-duration” spaceflight, the researchers monitored 17 astronauts before and after spaceflight over the course of seven years. The research was published in the journal Scientific Reports. Although it may not seem relevant to you personally while you are on Earth, the study is crucial to understanding bone health in general.

“Bone loss happens in humans—as we age, get injured, or any scenario where we can’t move the body, we lose bone,” says Dr. Leigh Gabel, Ph.D., assistant professor in Kinesiology, and lead author of the study.

“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,” Gabel says.

The researchers flew to Houston, Texas’ Johnson Space Center to scan the astronauts’ wrists and ankles before they launched into space, after they returned to Earth, and again after six and twelve months.

“We found that weight-bearing bones only partially recovered in most astronauts one year after spaceflight,” she says. “This suggests the permanent bone loss due to spaceflight is about the same as a decade worth of age-related bone loss on Earth.”

This loss happens because bones that would normally be weight-bearing on Earth, like your legs, don’t have to carry weight in microgravity—you just float.

“We’ve seen astronauts who had trouble walking due to weakness and lack of balance after returning from spaceflight to others who cheerfully road their bike on Johnson Space Center campus to meet us for a study visit. There is quite a variety of responses among astronauts when they return to Earth, says Boyd.

Former University of Calgary Chancellor and astronaut, Dr. Robert Thirsk, BSc (Eng)’76, Hon. LLD’09, MD, knows firsthand how bizarre the return to Earth can be. “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,” says Thirsk. “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.”

Some astronauts who flew on shorter missions, under six months, recovered bone strength and density in the lower body, compared to those who flew for longer durations.

Access to astronauts is rare—the study team includes two members from the European Space Agency (ESA), Dr. Anna-Maria Liphardt, Ph.D., and Martina Heer, Ph.D., as well as two from NASA, Dr. Scott Smith, Ph.D., and Dr. Jean Sibonga, Ph.D. The study was funded by the Canadian Space Agency and conducted in partnership with ESA, NASA, and astronauts from North America, Europe, and Asia.

As future space missions are exploring travel to more distant locations, the study’s next iteration will explore the effects of even longer trips, to support astronauts who may one day travel beyond the International Space Station.

As Thirsk says, “Astronauts will venture to deep space this decade and, in the coming centuries, humanity will populate other star systems. Let’s push back the frontiers of space exploration now to make this vision possible.”

Reference: “Incomplete recovery of bone strength and trabecular microarchitecture at the distal tibia 1 year after return from long duration spaceflight” by Leigh Gabel, Anna-Maria Liphardt, Paul A. Hulme, Martina Heer, Sara R. Zwart, Jean D. Sibonga, Scott M. Smith, and Steven K. Boyd, 30 June 2022, Scientific Reports.
DOI: 10.1038/s41598-022-13461-1

The study was funded by the Canadian Space Agency, Alberta Innovates, and the German Aerospace Centre.