Study recommends mandatory 3-year vacation so astronauts' brains can recover

Scientists studying the brains of astronauts have discovered startling changes brought on by microgravity that has led them to recommend a three-year break between missions.

The study, published last week in Scientific Reports, looked at the brains of 30 astronauts before and after space travel, determining that the brain's cerebrospinal fluid-filled ventricles expand anywhere from 11 percent to an additional quarter of their original size the closer astronauts get to the six-month mark of their missions.

While the expansion tapers off around the six-month mark, it doesn't necessarily end, said Rachael Seidler, one of the study's authors and a professor of applied physiology at the University of Florida.

"Many astronauts travel to space more than one time, and our study shows it takes about three years between flights for the ventricles to fully recover," Seidler said. It's not all bad news, though: "We were happy to see that the changes don't increase exponentially, considering we will eventually have people in space for longer periods."

Complementing Seidler's team's discovery is previous findings which determined that spaceflight causes an "upward shift of the brain within the skull," leading to "cortical crowding and narrowing of the sulci at the top of the brain" that can be seen in a shift of gray matter volume at the top of the brain and a decrease at the base.

With that in mind, Seidler and company are urging caution. "We don't yet know for sure what the long-term consequences of this is on the health and behavioral health of space travelers, so allowing the brain time to recover seems like a good idea," the professor said.

Not something we can just get used to

The study also looked at whether experienced and novice astronauts (defined as those that have or have not been to space, respectively) displayed any differences in their brains. If so, that would suggest gray matter changes caused by microgravity would be something humans could adapt to.

Unfortunately for our hopes of becoming an extraplanetary species, that doesn't appear to be the case. 

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Of the 30 astronauts surveyed, 18 had been to space prior to the study, while 12 were studied before and after their first flight. "Whole-brain analyses revealed no statistically reliable associations between post-flight changes … and whether a crewmember was a novice or experienced flyer," the team wrote in their report. 

One thing the team did notice was a change in how free water, cerebrospinal fluid and other liquid in the brain, didn't move as freely in the brains of astronauts who had been to space more than once, which may be harmful rather than a positive adaptation.

"Ventricular expansion during spaceflight may be compensatory, allowing the brain to accommodate fluid shifts towards the head that occur in microgravity," the researchers reported. Among astronauts who had made multiple trips to space, those that had less than three years of recovery between missions "showed little to no enlargement" of their brain ventricles following their mission, while those with more than a three-year gap between voyages showed expansion on return.

"With human spaceflight becoming more frequent and lengthy, these findings provide important insight … and suggest potential guidelines for future mission planning," the researchers concluded.

The rich need not worry, though. There aren't any appreciable brain changes for those that are in space for less than two weeks, so orbital tourism is still go for those with the means to get there. ®