Space Travel Can Change Astronauts’ Brains for Years

Fluid-filled cavities in the brain expand during spaceflight, and a new study shows that astronauts may need three years to recover

A person floats horizontally on a zero-gravity flight
Astronaut candidate Bobby Satcher during a zero-gravity flight on an aircraft in 2004. The microgravity in space affects the human body and even changes the brain. Smith Collection / Gado via Getty Images

Scientists have long known that traveling to space takes a toll on the body—but they’re still trying to figure out just what that means. But according to a new study, lengthy voyages outside Earth’s gravity can change an astronaut’s brain.

At the center of the brain are four, fluid-filled cavities called ventricles, which help keep the organ cushioned and floating in the liquid that surrounds it. During spaceflight, these ventricles expand by between 11 and 25 percent, as previous studies have shown.

In the new paper, published last week in the journal Scientific Reports, scientists assert that astronauts’ ventricles expand more during longer missions—and it could take more than three years for them to return to normal.

“How this impacts performance and long-term health is an open question,” Rachael Seidler, the study’s senior author and a space health researcher at the University of Florida, tells’s Charles Q. Choi.

But because of this uncertainty, “allowing the brain time to recover seems like a good idea,” she says in a statement.

Space travel, in some ways, can be harmful to human health. For one, the radiation exposure can increase cancer risk, damage the central nervous system and affect cognition, among other things, according to NASA. And the effect of microgravity adds to the list of risks, threatening loss of bone density, muscle atrophy and vision problems.

But long periods in space’s minimal gravity also affect the brain’s structure. Without gravity tugging everything down, the brain shifts upward in the skull, displacing the fluid around it within astronauts’ heads, per the paper. As a result, more fluid accumulates, and the brain’s ventricles expand to hold more of it, Seidler tells Science News’ McKenzie Prillaman.

For the new study, the researchers wanted to find out what factors affected the ventricles’ size. They tested whether mission length, past spaceflight experience and time between missions played a role. The team looked at the MRIs of 30 astronauts, taken both before and after space travel. Eighteen of the astronauts spent six months in space, while eight spent two weeks and four spent one year.

Astronauts who spent two weeks in space didn’t exhibit a noticeable change in their ventricles, the researchers found. And as the team hypothesized, those who spent more time in space had larger ventricles. But regardless of whether astronauts spent six months or a year in microgravity, they had similar levels of brain change, suggesting that ventricle expansion tapers off after six months.

Additionally, astronauts’ brains did not immediately recover following a mission. Six to seven months after astronauts returned from a six-month stint in space, their ventricles had only recovered by 55 to 64 percent compared to their pre-flight size.

If astronauts returned to space less than three years after their last flight, their ventricles did not expand as much after the more recent mission. This suggests the ventricles were still enlarged from previous flights and had not had enough time to go back to normal. Meanwhile, ventricles expanded more in astronauts who had not been to space for over three years.

This finding could mean that astronauts’ brains need at least three years to recover from long spaceflights. “This is a surprisingly long time,” Seidler tells

Scientists don’t know exactly what health effects might come from enlarged ventricles. However, the condition make make the ventricles struggle to drain fluid from the brain, either by becoming clogged or failing to fill with liquid, writes Time’s Jeffrey Kluger.

“I’m glad that the [study] authors took the first step and are looking at this question,” Donna Roberts, a neuroradiologist at the Medical University of South Carolina who was not involved in the research, tells Science News. “There are so many variables that could play into the brain changes that we’re seeing, and it’s hard to sort them out.”

Get the latest stories in your inbox every weekday.