NASA twins study reveals long-term spaceflight's impact on human health

NASA has published an integrated paper detailing the results of its Twins Study, which involved now-retired astronauts and identical twin brothers Scott and Mark Kelly. NASA called the findings "interesting, surprising and reassuring," detailing the changes in Kelly's body caused by his nearly year-long time on the International Space Station.

The Twins Study took place from 2015 to 2016 and was the first of its kind ever performed by NASA. The study involved astronaut Mark Kelly on Earth and his identical twin brother Scott Kelly in space. Upon Scott Kelly's return, NASA studied the effects space exposure had on his health by comparing his data to that from his brother, Mark.

A number of key findings have been detailed in NASA's study, including information about the effects space had on Scott Kelly's telomeres. According to the space agency, Scott's white blood cell telomeres were surprisingly longer in space, but then were shorter after returning to Earth. Six months later, the length returned to average; Mark Kelly's telomere length remained stable through the same period of time.

In addition, NASA says its study found that Kelly's immune system responded appropriately while in space, including in response to the flu vaccine. As the space agency previously stated, researchers also found variability in gene expression, with the majority of changes reverting to normal after half a year back on Earth.

The exception involved 'a small percentage' of genes related to DNA repair and the immune system, which didn't return to baseline after Kelly's time in space ended. NASA Headquarters Chief Health and Medical Officer J.D. Polk explained:

The Twins Study has been an important step toward understanding epigenetics and gene expression in human spaceflight. Thanks to the twin brothers and a cadre of investigators who worked tirelessly together, the valuable data gathered from the Twins Study has helped inform the need for personalized medicine and its role in keeping astronauts healthy during deep space exploration, as NASA goes forward to the Moon and journeys onward to Mars.

NASA has big ambitions for taking humans into space, including in long-term missions on the Moon and, eventually, to Mars. Technological hurdles are only one aspects of this goal, though — the space agency needs data on how time spent in space impacts the human body. Though at this time its Twins Study has a subject of only 1, the data remains priceless.