Now, in a new study published Monday in the Proceedings of the National Academy of Sciences, researchers discovered that months in space might trigger swelling in the brain that may, at the very least, result in problems with eyesight.
Intriguingly, these findings suggest that Russian cosmonauts suffered less than NASA astronauts, suggesting that some countermeasures against microgravity might prove more effective than others at supporting crews on long-term spaceflights.
WHAT DID THE SCIENTISTS DO? — The scientists analyzed brain MRI scans of 24 NASA astronauts and 13 Roscosmos cosmonauts before and within two weeks after roughly six months in orbit aboard the International Space Station. They also examined scans of seven NASA astronauts who took part in two-week missions on the space shuttle. They also investigated astronauts from the European Space Agency (ESA), but the small number scanned meant their results were not statistically significant enough to be included.
"It is one of the largest studies on space data and for sure one of the very few studies with NASA, ESA, and Roscosmos data," study co-author Floris Wuyts, a medical physicist at the University of Antwerp in Belgium, tells Inverse. "It comprises data of almost 10 percent of all people who went into space."
The researchers were especially interested in spaceflight-associated neuro-ocular syndrome, or SANS, which impacts roughly 40 to 60 percent of NASA astronauts on long-term missions onboard the International Space Station.
This set of symptoms includes a variety of changes to the eyes and brain, including swelling of the nerve as it enters the eye, folds in the retina, flattening of the back of the eye, blurry vision, a shift in the fluid around the brain, and a change in the shape of the pituitary gland.
The mechanisms behind SANS "are still not completely clear," study co-author Donna Roberts, a neuroradiologist at the Medical University of South Carolina in Charleston, tells Inverse.
WHAT DID THEY FIND? — The scientists found that long-duration spaceflights were associated with a swelling of perivascular spaces in the brain, which are fluid-filled compartments surrounding blood vessels. The researchers didn’t notice these changes in astronauts who were on short-term missions.
Eight of the NASA astronauts developed SANS. The researchers saw more perivascular swelling in their white matter, the parts of the brain and spinal cord made up mostly of bundles of nerve fibers and their fatty sheaths. The researchers suggested that microgravity-related changes in the way fluid moves around the body might lead to swelling in the white matter and thus boost the risk of SANS.
These changes were more conspicuous in NASA astronauts than in the Roscosmos cosmonauts, study co-author Giuseppe Barisano, a neuroscientist at the University of Southern California in Los Angeles, tells Inverse. This suggests the microgravity countermeasures that a space agency adopts might help protect the brain after long-term spaceflights.
For example, Russian cosmonauts undergo lower body negative pressure sessions beginning two weeks prior to landing that NASA and ESA do not — these shift blood from the upper to the lower body by placing a person in a cylindrical airtight metal tank that is sealed off around the pelvis, and a vacuum pump then reduces the air pressure around the legs.
In addition, NASA and ESA astronauts exercise with free weights on the International Space Station more often and with more massive loads when compared with Russian cosmonauts. Such workouts might lead to more fluid buildup in the brain.
WHAT’S NEXT? — Future research should focus largely on the impact of various exercises and microgravity countermeasures “by looking in detail at the time, duration, intensity and so on spent on the exercises and countermeasures to identify the true relationship,” Wuyts says. “Given the differences that we found between crews, we need to elaborate on what could be the cause of these differences.”
All in all, “these further studies may guide countermeasure usage for future space exploration missions, such as a trip to Mars,” study co-author Elena Tomilovskaya, a space Physiologist at the Russian Academy of Sciences’ Institute of Biomedical Problems in Moscow, tells Inverse.
“I believe this research highlights the importance of international cooperation in understanding the effects of long-term spaceflight on the human body,” Roberts says. “We believe international cooperation in space medicine research is essential to ensure the safety of our crews as we return to the moon and on to Mars.”