NASA astronaut and Expedition 65 Flight Engineer Mark Vande Hei, pictured May 22, 2021, broke the record for single-longest spaceflight by an American. A new study suggests long-duration spaceflight is equivalent to a decade of age-related bone loss on Earth. File Photo courtesy NASA | License Photo
July 1 (UPI) -- Scientists have long known that astronauts lose bone density while in space, but a study published this week found they only partially recover this loss one year after returning to Earth.
The researchers said the findings suggest long-duration spaceflight is equal to decades of bone loss in weight-bearing bones on Earth. The extent of the impact, though, varies depending upon the subject.
Bone loss happens because bones don't have to carry your weight in microgravity, meaning astronauts use them less, leading to weakening.
"Bone loss happens in humans -- as we age, get injured, or any scenario where we can't move the body, we lose bone," said Leigh Gabel, assistant professor in kinesiology at the University of Calgary and lead author of the study.
The researchers scanned and studied the wrists and ankles of 17 astronauts at Johnson Space Center in Houston before and after they spent time in space -- six months and 12 months post-return.
Gabel said the scans showed that astronauts weight-bearing bones "only partially recovered" a year after they returned to Earth. Astronauts who flew on missions shorter than six months had more recovery in bone density and strength compared to those who were in space longer.
"This suggests the permanent bone loss due to spaceflight is about the same as a decade worth of age-related bone loss on Earth," she said.
Steven Boyd, professor and director of the McCraig Institute for Bone and Joint Health at the Cumming School of Medicine, said the effects of long-duration spaceflight on astronauts' bones varies from person to person.
"We've seen astronauts who had trouble walking due to weakness and lack of balance after returning from spaceflight, to others who cheerfully rode their bike on Johnson Space Center campus to meet us for a study visit," he said.
The researchers published their findings in the journal Scientific Reports on Thursday.
The International Space Station is pictured from the SpaceX Crew Dragon Endeavour during a flyaround of the orbiting lab that took place following its undocking from the Harmony module’s space-facing port on November 8. Photo courtesy of NASA