Astronauts have distinct brain changes even months after returning to Earth

Plunged into freefall for months, our bodies adapt in ways that create a long list of health problems for space travelers.

The latest assessment of the warping effect of microgravity on our biology focuses on the spaces surrounding the blood vessels that run through our brains, revealing concerning changes that linger in astronauts between missions.

Researchers from across the United States compared a series of magnetic resonance images (MRI) of 15 astronauts’ brains taken before a six-month stay on the International Space Station and up to six months after their return.

Using algorithms to carefully assess the size of perivascular spaces (gaps in brain tissue believed to facilitate fluid balance), the team found that time spent in orbit had a profound effect on brain plumbing. For beginners, at least.

Among the group of veteran astronauts, there appeared to be little difference in the size of the perivascular spaces in the two scans taken before the mission and the four taken after.

“Experienced astronauts may have reached a kind of homeostasis,” says Juan Piantino, a neurologist at Oregon Health & Science University.

The results may not be so surprising given what we already know about how the brain warps when the constant tug of gravity is undone.

Previous studies of brain tissues and their fluid volumes have shown that they are slow to recover from being in space, with some changes persisting for a year or more.

Currently, astronauts rarely make more than a few space trips in their lifetime, typically hanging around for about six months at a time. Yet, as the commercialization of a space industry accelerates, all of that could change.

It will be useful to know if repeated trips make the damage worse or if the changes experienced on that first trip temporarily adapt the astronauts to a new kind of normal.

“We’ve all adapted to use gravity to our advantage,” says Piantino.

“Nature didn’t put our brains in our feet – it put them up high. Once you take gravity out of the equation, what does that do to human physiology?”

Even in the context of enlarged perivascular spaces, it is not yet entirely clear whether the change comes with appreciable health risks.

We tend to get the most out of this neurological drainage system when we sleep. The flow of fluids around our gray matter seems to play an important role in clearing away the waste products that build up during our most active hours.

Without these channels working efficiently, disruptive materials could build up, potentially contributing to increased risks of neurodegenerative diseases like Alzheimer’s disease.

It’s too soon to tell if microgravity is impacting the circulation of cerebrospinal fluid around our noggins, let alone if the changes in the shape of the channel network are significant. This may not even become obvious until researchers have a good-sized sample of veteran astronauts with substantial careers under their belts.

Learning about these small tweaks goes beyond the potential damage of off-world work in a space industry.

“It also forces you to think about some fundamental fundamental questions of science and how life evolved here on Earth,” says Piantino.

The ubiquitous pull of gravity isn’t just something we struggle with, after all. It’s a force we’ve evolved to use, helping with blood circulation and waste disposal, and potentially a variety of other functions we’ve barely considered.

By studying the subtle changes in health and anatomy in conditions we have never endured, we are almost certain to learn more about the diseases and disorders our bodies have been forced to contend with here- low.

This research was published in Scientific reports.

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