Space or stress? Astronauts in orbit are a little bit dumber, study shows

A recent study published in the scientific journal Frontiers in Physiology revealed that astronauts experience temporary slowing of cognitive performance during their missions in space. The research team, led by Dr. Sheena Dev at NASA's Johnson Space Center, studied 25 astronauts who spent an average of six months on the International Space Station (ISS). They found that while the astronauts did not suffer significant cognitive impairments or neurodegenerative changes, some cognitive processes, particularly processing speed, working memory, and attention, slowed down during their time in orbit.

The astronauts participated in ten cognitive tests designed to assess various cognitive capacities, such as processing speed, visual working memory, sustained attention, abstract reasoning, and risk-taking propensity. The tests were administered at multiple points: before the mission, early and later during the flight, and after returning to Earth. The researchers observed that the astronauts took longer to complete tasks assessing processing speed, working memory, and attention on the ISS compared to their performance on Earth. Despite the slowing in response times, the astronauts maintained the same level of accuracy throughout the mission.

"Even on Earth, processing speed, working memory, and attention are cognitive domains that can show temporary changes when an individual is under stress," Dr. Sheena Dev explained. "We found that the most vulnerable domains while astronauts are aboard the ISS are the same as those that are more susceptible to stressors on Earth," She added. The study noted that these cognitive changes did not persist after the astronauts returned to Earth, although processing speed took longer to return to normal.

Living and working on the ISS involves increased radiation, reduced gravity, sleep deprivation, cramped conditions, and complex tasks where a small error can have devastating consequences. These factors, collectively known as spaceflight stressors, are part of daily life for crew members and can impact cognitive abilities. Scientists have long known about the physical difficulties faced by the human body in space, such as radiation exposure, bone density loss, muscle atrophy, and detrimental effects on the heart, eyes, spine, cells, and overall physical fitness. However, the cognitive effects of long-term space travel are less well documented.

Elisa Raffaella Ferrè at Birkbeck, University of London, emphasized the importance of having clear data on the cognitive effects of space travel for future human spaceflight. "A mission to Mars is not only longer in terms of time, but also in terms of autonomy. People there will have a completely different interaction with ground control because of distance and delays in communication, so they will need to be fully autonomous in taking decisions. You definitely don't want to have astronauts on Mars with slow reaction time, in terms of attention-related tasks or memory or processing speed," she stated.

Jo Bower at the University of East Anglia in Norwich, UK, echoed these concerns, noting that while the specific decreases in cognitive performance are not necessarily a great cause for alarm, awareness of these changes is crucial. "It's not necessarily a great cause for alarm, but it's something that's useful to be aware of, especially so that you know your limits when you're in these extreme environments," she said. Bower highlighted the importance of self-awareness in performance, adding, "It's not just how you do in those tests, but also what your perception of your ability is. We know, for example, if you're sleep deprived, that quite often your performance will decline, but you won't realize your performance has declined."

The study observed that while processing speed remained slowed throughout the entire mission, other cognitive domains were less affected. " Other domains, such as memory, are less vulnerable to stressors," Dr. Dev mentioned.The research also found a decrease in risk-taking propensity during late flight and post-flight mission phases. The researchers noted that these effects might be linked to the unique stressors associated with space travel.

Previous research has indicated that extended spaceflight can have various effects on the human brain. Studies published in 2020 and 2017 showed that long-duration spaceflight may fundamentally alter the amount of cerebrospinal fluid in the brain and cause gray matter to both increase and decrease in different regions. The increased volume of cerebrospinal fluid remained for a full year after astronauts returned from space.

As NASA prepares to return astronauts to the Moon as part of its Artemis program, with plans to establish a sustainable human presence on the lunar surface and eventually travel to Mars, understanding the cognitive effects of space travel becomes increasingly important. Space agencies will need to develop strategies to mitigate the harmful downsides space travel can have on astronauts.

Dr. Dev provided an example of how stress can impact cognitive function, stating, "If you happen to have a really busy day but couldn't get much sleep the night before, you might feel like it's hard to pay attention or that you need more time to complete tasks." The study added that "exploratory analyses yielded no clear pattern of associations between cognitive performance and either sleep or ratings of alertness," suggesting that the observed cognitive slowing may not be directly linked to sleep deprivation or fatigue.

The Sun, New Scientist, and Gizmodo were among the outlets that reported on the study.

This article was written in collaboration with generative AI company Alchemiq