Researchers Uncover Impacts of Space Travel on Human Brain Functioning

The human body is not naturally adapted to cope with the harsh conditions of outer space, particularly microgravity, which can impact our physical wellbeing from top to bottom. The head, unsurprisingly, is of particular interest.

A fresh study, financially supported by NASA, delves into this issue further. The research, unveiled on Thursday, revealed that space explorers who spent at least half a year either on the International Space Station (ISS) or on NASA space shuttles experienced noticeable enlargement of their cerebral ventricles - the inner cavities of the brain that house cerebrospinal fluid.

This clear, water-like liquid circulates throughout the brain and spinal cord, cushioning the brain against sudden impacts and assisting in waste removal.

After examining brain scans of 30 space travelers, it was observed that a full recovery of the ventricles took around three years following such long-term missions. This indicates that a gap of at least three years might be beneficial between lengthy space missions.

"The concern is if ventricles do not get adequate time to recuperate from continuous missions, it may affect the brain's capacity to handle fluid shifts in microgravity. For instance, if the ventricles have already enlarged from a prior mission, they might be less adaptive and have limited space for further expansion and fluid shifts during the subsequent mission," stated Heather McGregor, a neuroscientist at the University of Florida and the study's lead author. The study was published in the Scientific Reports journal.

Enlargement of ventricles due to age, a result of brain shrinkage rather than microgravity, can be connected to cognitive deterioration.

Rachael Seidler, professor of applied physiology and kinesiology at the University of Florida and senior author of the study, stated, "The implications of ventricular enlargement in astronauts are currently unknown. We require more long-term health monitoring. The probable compression of adjacent brain tissue by this ventricular expansion is a concern." The brain undergoes changes in the absence of Earth's gravitational pull.

Seidler further added, "This seems to be a physical effect. On Earth, our circulatory systems include valves that prevent fluids from accumulating in our feet due to gravity. In a microgravity environment, the reverse happens - fluids shift towards the head. This shift of fluid towards the head is likely the cause of ventricular enlargement, and the brain positions itself higher within the skull."

The research included 23 male and seven female astronauts with an average age of approximately 47, hailing from American, Canadian, and European space agencies. Eight of them partook in space shuttle missions that lasted roughly two weeks, while eighteen served on ISS missions of around six months, and four were involved in ISS missions that stretched close to a year.

Astronauts on short missions displayed negligible changes in ventricular volume. However, those engaged in missions lasting six months or more exhibited ventricular enlargement. Interestingly, there was no notable difference between those who served for six months and those who completed a year.

"It appears that the majority of the ventricular expansion takes place during the initial six months in space, and then gradually starts to stabilize around the year mark," McGregor mentioned.

The fact that the ventricular enlargement does not intensify post six months could be a positive sign for potential future Mars missions where astronauts might have to endure two years of microgravity during their journey.

"Though this preliminary discovery is encouraging for maintaining astronauts' brain health during extended missions, it's crucial that we analyze MRI data from a broader astronaut population and after even longer missions," McGregor added.

Seidler noted that the lack of ventricular enlargement after short flights could be favorable news for those contemplating brief space tourism trips as this sector evolves.

The microgravity environment also leads to other physiological changes due to the decreased physical stress on the human body. These changes include bone and muscle wasting, modifications in cardiovascular function, issues with the inner ear's balance system, and a syndrome involving the eyes. An increased risk of cancer due to higher exposure to solar radiation that astronauts might face as they venture farther from Earth is also a matter of concern.