It's been understood for a while now that spending time in space can damage the bodies of astronauts. Famed retired Astronaut Capt. Scott Kelly has noted in both his public appearances and in his recently published memoir, "Endurance: A Year in Space," that he knew going into his final mission aboard the International Space Station, without a doubt, that his body and health would be permanently altered during the 340 days he spent orbiting Earth before coming home in March 2016.
Kelly knew from experience that he would be exposed to high levels of radiation, would endure muscle atrophy, the loss of bone density and other factors while in orbit and that he would go through signficant amounts of pain as his body re-adjusted to gravity once he returned, but now it is clear, according to a study recently published in the New England Journal of Medicine, that even the brain is altered by long trips in space.
In the study researchers scanned the brains of astronauts using magnetic resonance imaging to before and after the astronauts went up to space for stints of varying lengths of time aboard the ISS. The MRI scans found that astronauts who went for longer stays came back with altered brains.
An astronaut's body goes through a fluid shift once he reaches zero gravity, as fluids from the lower parts of the body shift to the upper parts of the body. This messes with everything from the internal organs to the inner ear. As astronauts stay in orbit their faces become puffy and their legs thin out, they get stuffy noses, are less thirsty and go through a dulled sense of taste. About 80 percent of astronauts get motion sickness during their first couple days in micro-gravity as well. And, of course, being outside the laws of gravity also effects the brain.
Of the 34 astronauts participating in the NASA-backed study (28 men and six women) 18 were sent to space on long-term missions that averaged to about 135 days in orbit on the ISS, while the others averaged only about 13 days in zero gravity during space shuttle launches.
The researchers found that 17 of the 18 astronauts who went on long-term missions came back with a narrowed central sulcus, the part of the brain that divides the region in charge of the input of sensory stimulus from the part of the brain in charge of motor function. Only three of the astronauts who went on short-term missions had the same issue.
The MRI scans also revealed an increase in cerebrospinal fluid and an upward shifting of the brain inside the skull. The extra cerebrospinal fluid puts more pressure on the brain and squeezes it so that the space between regions inside the brain is smaller. This fluid, which surrounds the brain, is meant to protect it and help the brain maintain normal functions.
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Any disturbance in the amount of cerebrospinal fluid alters cognitive function, and while the researchers behind the study still don't know for sure, they believe that long periods of time spent in zero gravity end up increasing the amount of blood and cerebrospinal fluid hanging around the brain.
While 12 of the astronauts who went on longer missions showed signs of an increase of cerebrospinal fluid at the top of the head, only one astronaut from the short-term group showed similar signs. The long-term group also had 12 long-term astronauts whose brains had shifted upward entirely, while there were none found in the short-term group.
In addition to these symptoms, three of the astronauts in the long-term group reported experiencing visual impairment and intracranial pressure syndrome, a relatively new issue that Kelly and other retired astronauts have been noting post-spaceflight. The VIIP and the changes in the brain may be related, researchers believe, since the three who reported VIIP also were found to have the narrowed central sulcus in their brains. (They think the eyes could act as a release valve for some of the pressure being placed on the head, which would result in the headaches and vision loss the astronauts have reported.)
Overall, this study has only unveiled the tip of the iceberg when it comes to examining and understanding the effects, both short-term and long-term, of sending astronauts out on missions that see them living in micro-gravity for months at a time, something that must be better understood before NASA is ready to actually send astronauts on the long trek to Mars.