The results of the "Twins Study" conducted by NASA to study the impact of space flight on human health, were published in the journal Science. Two identical twins, Mark and Scott, were the subject of this study, one of whom spent over 300 days inside the International Space Station.
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Having brought together about ten research teams from across the country, the "Twins Study" aimed to identify the physiological, molecular and cognitive changes that can occur in a human being exposed to the risks associated with space flight. To do this, NASA proceeded to compare a set of variables in two identical-twin astronauts, Scott Kelly, who went into space for 342 days, and his brother Mark Kelly, who remained on Earth.
The results of the "Twins Study" unveiled on April 11, 2019, and featured in an article in the journal Science, reveal interesting and surprising data on how the human body can adapt to extreme conditions in space life, and the consequences of space travel on the human body. This mission is only a preliminary study and should be followed by longer expeditions like roundtrip missions to Mars, which could last up to 3 years.
NASA recognizes that the Twins Study is the first of its kind to compare the molecular profiles of identical twin astronauts. Since identical twins share the same genetic makeup, twin studies allow scientists to study how human health is influenced by the environment around them, regardless of the physical changes that occur naturally due to genetic predisposition. With this research work, NASA seeks to ensure the health and safety of astronauts involved in the space conquest.
Telomeres represent the ends of each strand of DNA and have special characteristics to protect the chromosomes. Telomeres tend to shorten with age; however, factors related to lifestyle, stress and environmental exposure can also influence the rate at which this shortening occurs. One of the most striking findings of the NASA Twins Study is that Scott (who made the space trip) presented a change in the dynamics of telomere length during the space flight and a few days after landing. This makes it possible to assess the long-term risk of space missions to the health of astronauts.
Another parameter was also studied: the vaccine immune response. Scott received three influenza vaccines, each a year apart; the first on Earth, the second in space (the first time an astronaut receives a vaccine in space) and the third on Earth. The study revealed that Scott's body responded to the vaccine delivered in space in an appropriate manner. This important discovery allows NASA to ensure that the immune system would react appropriately in space if vaccination is required during long-term missions.
Samples taken before, during and after Scott's mission in space revealed some changes in gene expression. Mark has also experienced changes in gene expression on Earth, but these are not the same. The changes Scott experienced may have been associated with his long stay in space and most of them (about 91.3%) had returned to normal after six months of his return to Earth. It is suggested that some of the damage observed in DNA is due to exposure of the human body to radiation.
With regard to cognitive abilities, the majority of them (alertness of mind, spatial orientation, etc.) remained unchanged during Scott's stay in space, suggesting that astronauts can maintain a high level of mental performance during long periods of space missions. However, a decrease in speed and mental accuracy was observed after landing and persisted for six months. This could be related to re-exposure and adaptation to Earth's gravity, as well as Scott's busy days after the space mission.
Scott's body weight also decreased by 7% and his intestinal microbiome changed significantly during the flight with a return to normal after landing. Other results emerged from the study: inflammatory signs and thickening of vascular walls, changes in hydration status, genetic modifications, inflammation, etc.
We cannot send humans to Mars without knowing how space flights affect the body, including microbes traveling with humans on Mars," said Fred W. Turek, who conducted the microbiome study. "And we need to know as soon as possible. The objective is to send people to Mars in 2035, so we can't wait until 2033 to get this information."
This study could, therefore, help scientists better understand the risks of long space missions to astronauts' health and could also help guide NASA's Human Research Program studies for years to come.