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Twins study: How one-year mission affected astronaut’s health

(CNN)What happens to the human body after a year on the International Space station, floating in zero gravity? The Twins Study — comparing data from before, during and after astronaut Scott Kelly’s mission in space with those of his identical twin brother, retired astronaut Mark, back on Earth — is giving researchers a better idea than ever before.

A focus on telomeres, the repetitive sequences at the end of a chromosome to protect it from deteriorating or fusing with other chromosomes, in the twins’ white blood cells revealed a surprise: Typically, telomeres decrease in length as someone gets older. But Scott’s increased while he was in space. When he returned to Earth, they shortened again.
For now, the researchers believe the change could be linked to an increase in exercise and decrease in calorie intake while on the station.
They also looked at telomerase, which repairs and lengthens the telomeres, for both men. This response increased in both Scott and Mark in November 2015, possibly related to a “significant, stressful family event” happening around that time.
Scott experienced declining bone formation, but levels of a healing hormone that helps with bone and muscle health increased, most likely due to all of the exercises astronauts perform in space every day to combat bone and muscle loss. His levels of the stress hormone cortisol remained normal, but he had a spike in inflammation soon after landing on Earth — most likely because of the stress of re-entering the atmosphere.
Though Scott and Mark have differences in the bacteria in their digestive systems, which was to be expected because they were living in different environments and eating different food, two of the main bacterial groups switched dominant positions in Scott’s microbiome between his time in space and on Earth.

The stressors of space

When it comes to a mission to Mars, the first actions astronauts take on the surface of the Red Planet could be the most crucial. But after spending six months traveling through deep space, they might have difficulty performing tasks quickly and efficiently, even if those actions would be vital to life support.
Scientists have long aimed to improve astronauts’ sleep duration and quality. With improved scheduling, fewer work shift changes and the fact that space station construction is completed, the one-year astronauts got an average of seven hours of sleep each night. Astronauts with shorter missions on the station averaged about six hours of sleep.
All of the results are preliminary findings, and research continues. A summary and in-depth research articles are expected later this year.

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“The preliminary results from the year-long ISS expedition and the associated Twin Study … have not identified any show-stoppers for longer human spaceflight missions,” NASA Human Research Program chief scientist John Charles said in a statement.
“Some of the results, such as the unexpected increase in telomere length in Scott Kelly, require additional analysis and correlation with the results of other investigators, and may prove to be an artifact or transient change. Overall, the preliminary results are reassuring that a year in space is not significantly more stressful than 6 months in space. However, more definitive insights must await the further analysis of the samples and supporting data, the correlation of findings among all the investigators, and future long-duration ISS missions with these and other genetic investigations — although, almost certainly no more twins, unfortunately.”

Read more: http://www.cnn.com/2017/02/01/health/astronaut-twins-study-preliminary-results-trnd/index.html