Space missions up to 6 months in duration cause increasing expansion of ventricles in the brain.
Leaving the Earth’s atmosphere and the comforting pull of gravity is not without its risks, many of which we are still learning about. A collaboration of researchers led by Rachael Seidler (University of Florida, FL, USA) has recently reported that ventricle expansion in the brain increases with extending periods in space and ventricles do not fully recover if inter-mission intervals are less than 3 years.
Spaceflight induces physiological changes, including an upward shift of the brain within the skull, which displaces cerebrospinal fluid. How mission duration, number of prior missions and time between missions impacts changes in the brain is not understood, as well as how long it takes for the brain to return to normal.
There are four ventricles at the center of the brain, which are cavities that are filled with cerebrospinal fluid to protect the brain. Previous studies have found that an 11–25% expansion in ventricle volume can occur due to space flight. It is thought this is a compensatory mechanism that allows the brain to accommodate fluid shifts that occur due to microgravity. Ventricle enlargement is associated with aging; however, the rate at which this occurs during spaceflight exceeds the rate of enlargement due to aging.
Our brains are optimized to live with gravity, but how does it adapt to the different laws of physics experienced up in space?
The researchers of this study took MRI scans of 30 astronauts pre- and post-spaceflight to monitor changes in their brains. This included 8 astronauts on 2-week missions, 18 astronauts on 6-month missions and 4 astronauts on longer missions.
For astronauts in space for 2 weeks, no noticeable changes in ventricle volume were observed. Ventricle expansion increased over longer missions, but the effect plateaued after 6 months in space. After 6–7 months back on Earth, the brains of astronauts who had been in space for 6 months had only recovered by approximately 55–64% compared to their pre-flight size.
Additionally, there was little ventricle enlargement observed between pre-flight and post-flight MRI scans of astronauts who had less than 3 years between space flights. The authors propose this is because their brains had not fully recovered from previous flights to space and that this incomplete recovery might have a negative impact on subsequent flights.
These findings could be used to improve guidelines for future mission planning, for example allowing enough time between space missions for the brain to recover.
While humans are going up to space for increasing periods of time to explore our galaxy, and trips to Mars come within reach, this study is a good reminder that humans are built for gravity and living without it does affect our bodies.
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