The Herman Trend Alert

May 1, 2019

Humans in Space

The International Space Station (ISS) has been in continuous operation for 18 years. For this entire time, humans have been living and working on the station, Thanks to the NASA Twin Study, we now have a general concept about what happens to our human bodies in zero gravity.

NASA's Twin Study 

NASA was fortunate that Scott and Mark Kelly, a pair of identical twins, qualified for the astronaut program. NASA wanted to study the effects of being in space on the human body. Scott spent 340 days on the ISS, while Mark stayed on Earth for the duration of this study, though he has previously spent short stints in space. The NASA Twin Study worked because the astronauts shared the same basic genetics. Thus, scientists had an extraordinary chance to study the effects of being in space on the body.

The Twin Study insights from zero gravity

Our hearts change shape, reducing the amount of oxygen the blood can absorb and transport. Without gravitational challenge for long periods, our bones and muscles weaken. Fluids increase pressure in the eyes by rushing towards our heads. The longer people remain in space, these symptoms seem to worsen.

Some of Kelly's genetic changes were surprising

As we have discussed in the past, "telomeres" (the threads at the ends of our chromosomes) are a definite indication of the aging process. As we grow older telomeres shorten. Surprisingly, Scott Kelly's telomeres became longer in space; this lengthening is thought to be a protective response. However, within months of his return, Kelly's telomeres appeared "frayed", suggesting that some of his telomeres had disintegrated completely. Short telomeres typically correlate with age-related diseases such as heart disease and cancer. But the jury is still out about whether Scott is now at higher risk for these health problems.

Scott Kelly experienced numerous problems

According to one of the researchers, whose team worked on genomics, "Gene expression changed dramatically; in the last six months of the mission, there were six times more changes in gene expression than in the first half of the mission." Due to fluid buildup, Scott had problems with his eyes, unlike earth-bound Mark. In space, Scott had "puffy face" syndrome, due to cardiovascular changes and his immune system also responded to the stress. Moreover, his kidney function deteriorated, and it could have led to dehydration and kidney stones, although it did not. Finally, when Scott took a battery of cognitive tests, he performed worse in nearly all of areas except for spatial orientation after his space flight; both his speed and accuracy of reasoning suffered for at least six months after returning to earth. Scientists aren't certain what caused this poor performance; it could have been the trauma of re-entry or the demand for astronauts to participate in research studies and media events

Most problems were not permanent

However, over 91 percent of expression changes reverted back to baseline for Scott within six months after he returned home. The team concluded, "Overall, these data show plasticity and resilience for many core genetic and biological functions."

The limits of extrapolation

The challenge is that these results and conclusions may not be true for everyone. The team acknowledged, "We really can't say if any of the results are due to space travel or coincidence." However, their data do point the way to areas for future study involving other astronauts. This research was a first step to help researchers understand and counteract the negative health effects of space.

Only the beginning

The NASA Twin Study was a start. With long-term, commercial spaceflight on the horizon, NASA and others are eager to take the next steps. We will surely need more studies examining the health impact of even longer spaceflight in the future to consider traveling to Mars and beyond.

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