The concept of space tourism has been gaining momentum over the past few years, with 2021 bringing a series of historic flights. This includes SpaceX’s first all-civilian flight in September and William Shatner’s trip on Blue Origin’s New Shepard Crew Capsule last week, which made the 90-year-old Star Trek star the oldest person to fly in space. While these flights lasted just a few days or a few minutes, long-term stays in microgravity may become more common, and the health effects they may have are yet to be fully understood. A recent study by researchers at the University of Gothenburg, conducted using blood samples from five Russian cosmonauts, showed that long periods of time away from Earth could cause damage to brain cells.
The researchers drew blood from the five male cosmonauts, whose mean age was 49 years, 20 days before they each set off for months-long missions on the International Space Station (ISS). The team then collected follow-up blood samples one day, one week, and about three weeks after the cosmonauts returned to Earth, with the average time spent in space being about 169 days. The samples were tested for five biomarkers associated with brain damage: neurofilament light (NFL), glial fibrillary acidic protein (GFAP), total tau (T-tau) and two amyloid beta proteins. The results showed that the concentrations of three of the biomarkers — NFL, GFAP and Aβ40 — were elevated following the long-term ISS stays.
The peak readings did not occur simultaneously for each cosmonaut after returning to Earth, but the biomarker trends still broadly tallied over time, the researchers said. Previously neuroimaging studies of individuals who have spent extended periods of time in space have hinted at potential detrimental effects to the brain, and additional MRI scans and clinical tests of the cosmonauts also appeared to show changes in their brain function. The researchers noted, however, that the sample size is small and additional studies can further point toward which aspects of space travel cause these changes. This study was published in JAMA Neurology.
“This is the first time that concrete proof of brain-cell damage has been documented in blood tests following space flights. This must be explored further and prevented if space travel is to become more common in the future,” said senior coauthor Henrik Zetterberg. “To get there, we must help one another find out why the damage arises. Is it being weightless, changes in brain fluid, or stressors associated with launch and landing, or is it caused by something else? Here, loads of exciting experimental studies on humans can be done on Earth. If we can sort out what causes the damage, the biomarkers we’ve developed may help us find out how best to remedy the problem.”
Zetterberg and his colleagues are currently planning follow-up studies and further collaborations with national and international space research institutes. In addition to neurological changes, previous studies have shown that space travel can have effects on muscle and bone mass, vision and gut microbiota.