The health challenges astronauts Butch Wilmore and Suni Williams face after 9 months in space

On June 5, 2024, astronauts Butch Wilmore and Suni Williams embarked on a brief mission to the International Space Station. But equipment failures turned what was supposed to be an eight-day trip into a grueling 9 month spaceflight.

This week, Wilmore and Williams finally returned to Earth. While their safe return is cause for celebration, the journey doesn’t end when astronauts touch down on Earth. They now face the significant task of recovering from the physical and psychological toll of long-duration spaceflight.

As part of the University of Florida’s ongoing research into astronaut health, Rachael Seidler, Ph.D., a leading expert in spaceflight-associated health changes, is studying the long-term effects of space travel on astronauts’ brains and bodies. Seidler’s research focuses on understanding how the central nervous system and brain structure adapt to the challenges of space travel, as well as how these changes affect performance, balance, and mobility once astronauts return to Earth.

“While the physical and psychological challenges astronauts face after returning from long-duration space missions are well-documented, the research we do at UF is helping us understand the intricacies of their recovery process,” said Seidler, deputy director of the Astraeus Space Institute at UF. “By following astronauts like Butch and Suni before, during, and after their missions, we can track how the human body responds to the extreme conditions of space.”

Behavioral and Brain Changes Post-Flight

Seidler’s research tracks astronauts’ physical and neurological recovery by observing them both during their missions and after they return.

"One of the most immediate challenges astronauts face when they return to Earth is mobility and balance. These issues often recover more quickly compared to others, but it takes time for astronauts to readjust to gravity,” Seidler said. "The balance, mobility, and walking difficulties astronauts experience during the first weeks back are typically resolved in a short period, but brain function and structure require longer recovery periods."

Seidler’s research indicates that astronauts’ brains exhibit compensation when they return to Earth following spaceflight. This compensation occurs through the recruitment of additional neural pathways in order to return to their preflight performance levels. However, the recovery of brain function is a gradual process. "This brain functional compensation is typically no longer observed within one to six  months post-flight," Seidler said.

However, not all changes are reversible. "Brain structural changes, particularly related to fluid shifts in space, show little to no recovery even after six months to a year," Seidler said. Two significant structural changes include the brain physically sitting higher in the skull and the expansion of the brain’s ventricles — fluid-filled cavities in the brain — which can increase in volume by 25% or more. These changes are thought to result from the fluid shifts caused by microgravity, and they present long-term health considerations for astronauts.

Long-Term Health Effects: Understanding the Impact

As Wilmore and Williams embark on their recovery journey, the long-term impact of these changes becomes a critical focus for researchers like Seidler. "The long-term health impacts are crucial to understand because they could affect how astronauts recover and perform in their daily lives post-mission," she said.

Seidler’s team at UF is conducting a new study in which they are tracking astronauts for up to five years post-flight to better understand these long-term effects. "We’ve had astronauts in space for up to a year, and we know how to manage their physical health during those missions," Seidler said. "But the effects of space on the brain and body extend beyond the mission, and our work helps inform strategies to manage recovery."

Collaborating with NASA and Studying Spaceflight-Associated Neuro-Ocular Syndrome

Seidler's work is also part of a broader collaboration with NASA and other scientists to assess astronaut long-term health. The project is particularly focused on Spaceflight-Associated Neuro-Ocular Syndrome, which affects up to 70% of astronauts. This condition involves structural changes to the eye and optic nerve, leading to vision problems that may impact astronauts’ function.

"Neuropsychological assessments can help to measure astronauts’ brain health, while studies of the ocular system help identify potential vision issues that may arise during and after long-duration space missions," she said.

Simulating Space Conditions on Earth

In addition to studying astronauts on Earth and in space, Seidler’s team conducts experiments to simulate the effects of spaceflight on human physiology. The UF lab runs experiments in head-down tilt bed rest studies, which keep participants lying down for weeks to months at a time to simulate the lack of gravity. "This type of study helps us understand how fluid shifts in the body during space travel affect mobility, balance, and brain structure," Seidler explained. "In addition, other publications have reported that astronauts describe that vestibular galvanic stimulation feels similar to what they experience when they first arrive in space and when they return to Earth. We have equipment to induce these effects in the lab."

Looking Toward the Future

As space missions continue to grow longer and more complex, UF’s research is more important than ever. "We’re studying these issues now to ensure that future astronauts are prepared for the physical and cognitive challenges that await them in deep space," Seidler said.