Final Results of NASA Twins Study Show How Scott Kelly Changed After a Year In Space

The final findings of the NASA Twins Study, which compared 50-year-old astronaut Scott Kelly, who spent a year aboard the International Space Station in 2015, and his identical twin brother, who stayed on Earth, were published in Science. Gizmodo reports: NASA found that Scott Kelly was about as mentally, physically, and genetically healthy as his brother during his trip to space, and that the vast majority of small changes spotted in Scott (relative to himself before the mission) went back to normal within six months time. But the differences seen in Scott while up in space and after his return home could provide NASA important leads on how to keep astronauts safe during longer missions to Mars and beyond.

Preliminary results from the study were released in 2017. But it was the second round of findings, released in January 2018, that really caught the attention of media outlets, some of which misrepresented what was found. In particular, outlets like Newsweek reported that a whopping 'seven percent of [Scott Kelly's] genes did not return to normal after he landed.' Others implied that Scott Kelly had become a different person from his twin brother. But the researchers were never talking about a seven percent difference between the twins' genes. They were saying that some of Scott Kelly's genes had changed in their expression -- the carrying out of instructions in a cell's genome -- during his time up in space. And that roughly 7 percent of this overall change in gene expression could still be seen six months after he returned home. The remaining change in gene expression six months out was actually closer to 10 percent, but NASA clarified that this was still a relatively tiny change in his epigenetics. 'Given that the majority of the biological and human health variables remained stable, or returned to baseline, these data suggest that human health can be mostly sustained over this duration of spaceflight,' said NASA in a statement.

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