Microgravity and other variables can disrupt our physiology from head to toe, with the brain being the main worry.
NASA-funded research clarifies the issue. On Thursday, researchers reported that astronauts who spent six months on the International Space Station (ISS) or NASA space shuttles had considerable cerebral ventricle growth.
This clear fluid surrounds the brain and spinal cord. It protects the brain from shock and eliminates waste.
According to brain scans of 30 astronauts, it takes three years for the ventricles to fully recuperate after such travels, indicating a three-year gap between larger space missions.
If the ventricles don’t have enough time to recuperate between missions, microgravity fluid changes may affect the brain.
For example, if the ventricles are already enlarged from a previous mission, they may be less compliant and/or have less space to expand and accommodate fluid shifts during the next mission,” said University of Florida neuroscientist Heather McGregor, lead author of the Scientific Reports study.
Brains change under weightlessness.
“This seems mechanical,” Seidler added. “On Earth, our vascular systems have valves that prevent gravity from pooling all our fluids at our feet. Fluids go to the head in microgravity. This headward fluid transfer presumably causes ventricular enlargement, raising the brain within the skull.”
23 male and seven female U.S., Canadian, and European astronauts, average age 47, participated in the study. Eight took two-week space shuttle trips. Eighteen had six-month ISS deployments and four had one-year missions.
Short-term astronauts had little ventricular volume change. Astronauts who flew six months or longer enlarged, but there was no difference between those who flew a year.
“This suggests that most ventricle enlargement occurs during the first six months in space, then begins to taper off around the one-year mark,” McGregor said.
After six months, enlargement did not worsen, which is excellent news for prospective Mars missions that may last two years in microgravity.
“This preliminary finding is promising for astronaut brain health during long-duration missions,” McGregor added.
As space tourism expands, Seidler noted that short flights did not cause growth.
The lessened physical burden in microgravity has various physiological impacts. These include bone and muscle atrophy, cardiovascular abnormalities, inner ear balance difficulties, and eye dysfunction. Another issue is increased cancer risk from solar radiation exposure as astronauts go farther from Earth.