Study explores effects of extended spaceflight on brain

The researchers found that while all of the astronauts and cosmonauts they studied had a similar level of cerebrospinal fluid buildup in the brain, along with reduced space between the brain and the surrounding membrane at the top of the head, there was a noteworthy difference when it came to the Americans. They had more enlargement in the perivascular spaces in the brain, passages that serve as a cleaning system during sleep. That's something the researchers say warrants further investigation.

Donna Roberts, M.D., a neuroradiologist at the Medical University of South Carolina who helped lead the study, said a challenge when it comes to exploring the effects of spaceflight has been that there aren't many people in the U.S. who have traveled to space. Combining information about NASA astronauts with that of Russian cosmonauts and astronauts from the European Space Agency gave the study depth.

"By putting all our data together, we have a larger subject number. That's important when you do this type of study. When you're looking for statistical significance, you need to have larger numbers of subjects."

The study focused on 24 Americans, 13 Russians and a small, unspecified number of astronauts from the ESA. It used MRI scans of their brains before and after six months on the International Space Station to evaluate changes in the perivascular spaces.

Lead researcher Floris Wuyts, Ph.D., a professor at the University of Antwerp in Belgium, put the scope of the project in perspective. "I think it is one of the largest studies on space data, and for sure, one of the very few studies with NASA, ESA and Roscosmos data. It comprises data of almost 10% of all people who went into space." Roscosmos is the Russian space corporation.

Fellow researcher and neuroscientist Giuseppe Barisano, M.D., Ph.D., who works at the University of Southern California, said they looked for differences between the crews. "And in this analysis, we found an increased volume of fluid-filled channels in the brain after spaceflight that was more prominent in the NASA crew than in the Roscosmos crew."

Roberts explained what that might mean. "An important implication of our findings is that the volume of fluid-filled channels in the brain of astronauts is linked to the development of the spaceflight-associated neuro-ocular syndrome, a syndrome characterized by vision changes and whose mechanisms are still not completely clear."

But space physiologist Elena Tomilovskaya, Ph.D., of the Russian Academy of Sciences, said further study is needed to determine if there are clinical implications for future flights. "We need to understand how specific microgravity-countermeasure usage, exercise regimes, diet and other factors may play a role in the differences we found between crews."

Roberts agreed. "It is important not to speculate about pathology or brain health problems at this time. The observed effects are very small, but there are significant changes when we compare the post-flight scans with the preflight scans," she said.

The idea for the large study came about as the scientists gathered at annual meetings held by NASA and ESA. "Independently, we had previously reported similar changes in space crews at post-flight brain MRI, including enlargement of the cerebral ventricles. We discussed our findings and realized how valuable it would be to perform a joint analysis of our data. I would like to point out that Dr. Wuyts, in particular, was instrumental in organizing our group, which met regularly for two years to carry out this analysis," Roberts said."I believe it highlights the importance of international cooperation in understanding the effects of long-term spaceflight on the human body. In fact, we believe international cooperation in space medicine research is essential to ensure the safety of our crews as we return to the Moon and on to Mars."

The study, "The effect of prolonged spaceflight on cerebrospinal fluid and perivascular spaces of astronauts and cosmonauts," was funded by the Russian Academy of Sciences, NASA, ESA, the Belgian Science Policy Prodex, FWO Flanders and the National Institute of Mental Health at the National Institutes of Health in the U.S.