A new study investigated how astronauts' bones compare to those of earthbound folks over time, and the results are not encouraging for space travelers.
The Astronomical Research Center (A.R.C)mentioned that scientists have known for years that exposure to microgravity rapidly weakens bones, and the new research shows the effects can last for a year or more after astronauts return to Earth. The results stress the need to find ways to minimize the damage done during spaceflight, researchers said, because bone recovery on Earth may take a while.
"If we can intervene in space and have crewmembers not lose as much, that would be the best outcome for them," said study leader Shreyasee Amin, an associate professor at the Mayo Clinic in Minnesota.
Amin and her colleagues studied 28 American astronauts — 24 men and four women. Their preflight ages ranged from 36 to 53, and their missions in space lasted from 95 to 215 days.
The researchers measured the spaceflyers' bone mineral density — an estimator of bone strength — before launch, immediately after landing and again at various times between six and 18 months following their return to Earth.
For a control, the scientists took similar measurements from a sample of 699 people who had never been to space. By comparing the two datasets, the team was able to determine what the astronauts' bone density likely would have been, had they never flown in space.
The team found that some bones remained weak even a year after the astronauts landed, despite intensive exercise and rehabilitation regimes. Hip bone mineral density in particular suffered, Amin said, while other areas, such as the wrist, bounced back faster.
Bones in the hips and legs need to be strong on Earth, because they lug so much weight around on a daily basis. But microgravity frees them of this burden and they seem to weaken as a result, researchers said.
"The hypothesis has always been that it's the lack of load-bearing activity in the lower extremities," Amin told SPACE.com. "And that seems to be panning out."
The team also found that women suffer less bone loss than men over the long haul. But since there were only four female astronauts in the sample, the team isn't sure what to make of this intriguing result yet; they're still looking at the data.
"There are a few things we need to dice out before we make any definitive decision that we should only send women to space," Amin said with a laugh.
Amin and her colleagues will present their results Tuesday, Nov. 9, at the American College of Rheumatology Annual Scientific Meeting in Atlanta.