Floating in space may sound like fun, but doing so for a long time takes a huge toll on your body. According to a new study published in the journal Scientific Reports, spending just a few months in space changes astronauts’ bones , leading to loss of density equivalent to what most humans would lose in a couple of decades here on Earth. Perhaps most worrying of all, after a year, many astronauts do not fully regain lost bone mass.
“Bone loss happens in humans: As we age, get injured , or in any setting where we can’t move our bodies, we lose bone,” says Leigh Gabel, assistant professor of kinesiology and lead author of the study. “Understanding what happens to astronauts and how they recover is incredibly rare. It allows us to see the processes that happen in the body in such a short time. We would have to follow someone for decades on Earth to see the same amount of bone loss.”
A concern for future missions to Mars
Previous research has shown that astronauts lose 1% to 2% of their bone density for every month they spend in space, as the lack of gravity takes pressure off the legs when it comes to being unable to stand and walk. The fact of not supporting weight in the absence of gravity, greatly affects the bones.
The new research scanned the wrists and ankles of 17 astronauts before, during and after a stay on the International Space Station (ISS). The bone density the astronauts lost was equivalent to what they would lose in several decades if they returned to Earth, said study co-author Steven Boyd, of the University of Calgary in Canada and director of the McCaig Institute for Bone Health and the joints.
Most astronauts demonstrated incomplete recovery of bone density, strength, and trabecular thickness in the weight-bearing distal tibia. After a year back home, nine astronauts had still not regained the density of their tibiae. The total bone loss in the nine subjects was comparable to the decade-long bone loss faced by older people on Earth.
“Understanding what happens to astronauts and how they recover is incredibly rare. It allows us to see the processes that happen in the body in such a short time. We would have to follow someone for decades on Earth to see the same amount of bone loss,” explains Gabel.
Incomplete recovery of bone density and strength was more pronounced in astronauts who flew longer missions, for whom bone loss after spaceflight was significantly greater than in astronauts on shorter missions ( less than 6 months). .
“We have seen astronauts who had trouble walking due to weakness and poor balance after returning from a space flight, to others who joyfully rode their bikes across the Johnson Space Center campus to meet us for a study visit” Boyd clarifies.
Considering that we plan to venture on long-duration missions to Mars and beyond, it is extremely important to consider how this type of trip can affect our body. We must consider how weightlessness will affect our bodies in the short and long term to avoid significant and long-lasting after effects. The more time we spend in space, will this effect continue to worsen over time? Scientists don’t know, but we need to find out.
Referencia: Gabel, L., Liphardt, AM., Hulme, P.A. et al. Incomplete recovery of bone strength and trabecular microarchitecture at the distal tibia 1 year after return from long duration spaceflight. Sci Rep 12, 9446 (2022). https://doi.org/10.1038/s41598-022-13461-1
