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Elevated biomarkers for neurodegeneration found in astronauts returning from space travel

A new study, which assessed five Russian cosmonauts who had stayed on the International Space Station (ISS), found that the astronauts presented significantly elevated levels of biomarkers for brain degeneration.

For as long as we’ve been launching astronauts into space, scientists have been studying how spaceflight affects the human body. However, a new study shows that spaceflight may have unexpected degenerative effects on the human brain.

The new research was published in the journal JAMA Neurology, and conducted by scientists from the Sahlgrenska Academy’s Institute of Neuroscience and Physiology, in collaboration with colleagues in Moscow and Munich. The researchers tracked five male Russian cosmonauts aboard the International Space Station (ISS), which orbits 400 kilometers above Earth’s surface.

Long periods of time spent in space have long been recognized to have negative consequences on the body. Atrophic muscles, decreased bone density, declining eyesight, and alterations to the microbiome in the stomach are among the unfavorable effects.

In the new study, blood samples were obtained from the cosmonauts 20 days prior to their launch to the International Space Station. The subjects spent an average of 169 days in space (approximately five and a half months). The average age of the participants was 49. Follow-up blood samples were obtained three times following their return to Earth: one day, one week, and roughly three weeks after landing. The researchers looked at five indicators for brain injury. Neurofilament light (NFL), glial fibrillary acidic protein (GFAP), total tau (T-tau), and two different amyloid beta proteins were the proteins studied.

Three of the measured biomarkers — NFL, GFAP, and the amyloid beta protein A40 — were significantly higher after the subjects returned from space. Although the peak values did not occur at the same time when the men returned to Earth, their biomarker levels all followed a similar pattern over time.

The concentration of neurofilament light chain (NFL) in cerebrospinal fluid and blood has been reported to rise in CNS and peripheral nervous system disorders associated with axonal damage or degeneration. Additionally, Glial-fibrillary-acidic-protein (GFAP) has recently garnered a lot of interest as a potential biomarker in the clinical world. The diseases associated with the presence of GFAP in blood have a significant impact on the human central nervous system.

Dr. Henrik Zetterberg, one of the authors of the study stated, “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. To get there, we must help one another to 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.”

Zetterberg and his coauthors, Nicholas Ashton and Professor Kaj Blennow, are presently exploring follow-up studies with other study participants.

“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 says.


The study was published in JAMA Neurology, on October 11th, 2021.

Abstract. Long-duration spaceflight has a widespread effect on human physiology. The past decade first revealed eyeball alterations, and then neuroimaging studies hinted at potentially detrimental effects on the brain. Expansion of cerebrospinal fluid spaces occurs at the cost of the gray and white matter compartment. A neurobiological integrity assessment of the brain’s tissues after prolonged exposure to microgravity has never been conducted, to our knowledge. Therefore, we investigated the longitudinal course of blood-based biomarkers representing the brain parenchyma in long-duration spaceflight.

Eulenburg P, Buchheim J, Ashton NJ, et al. Changes in Blood Biomarkers of Brain Injury and Degeneration Following Long-Duration Spaceflight. JAMA Neurol. Published online October 11, 2021. doi:10.1001/jamaneurol.2021.3589

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