After a year-long mission of studying a pair of identical twins, one in orbit and one on Earth, researchers have a fresh batch of questions on what exactly long duration spaceflight does to the human body. We still don't know the full impact.
From March 2015 to March 2016, now-retired Nasa astronaut Scott Kelly spent 340 days on the International Space Station collecting detailed medical data on the effects of long duration spaceflight. But unlike most astronauts, Kelly came with his own scientific control on Earth: his identical twin brother, retired astronaut Mark Kelly. Ten scientists conducted detailed interdisciplinary researchers on the duo, with the results published today in the journal Science.
Most of the findings met expectations. “We reconfirmed a lot of the things,” says Steven Platts, deputy chief scientist for Nasa's Human Research Program. But Susan Bailey, biologist at Colorado State University and a principal investigator for study was surprised by the results of the astronaut's telomeres – a part of our DNA.
“Telomeres are a barrier so that you help to maintain the stability of your chromosomes,” explains Bailey. Telomeres have been compared to small plastic sheaths on the end of shoelaces that keep them from unravelling, but they protect chromosomes, she says. On Earth, it’s well-understood that telomeres get shorter with age or stress, so the natural assumption was that they’d get far shorter in astronauts braving the hostile environment of long-duration spaceflight.
“Astronauts are exposed to all of these things would really act together to accelerate the process of telomere shortening,” says Bailey. “We were wrong.”
Scott Kelly’s telomeres getting longer in space compared to his groundbound brother was the most startling result. “That couldn't have been more of a surprise,” Bailey says. “It was exactly the opposite of what we imagined going into the study.”
Even more surprisingly, the abnormality was restricted to just the time Scott Kelly was in space, with his telomeres shortening rapidly and dramatically within 48-hours of his return to Earth. “Whatever it is, is very specific to spaceflight,” says Bailey. “It's a very dynamic process,” says Platts. “Much more dynamic than a lot of people were thinking,” Platts agreed.
As for what that process is, researchers aren’t quite sure. It could be an artifact of the healthier lifestyles of astronauts on station. “[Astronauts] have a very defined diet even if they don’t like it too much,” says Bailey. Kelly also explained that his workout regime in orbit was far more rigorous than his terrestrial habits. “Exercising twice a day six days a week is kind of a requirement or your bones will turn to dust,” Kelly says. This contrary juxtaposition – space being a harsh environment, yet life on the space station supporting healthier habits – may partially explain the findings, although it doesn’t explain why Kelly’s telomere length shortened so quickly after landing.
Instead, it may be a strange sampling bias, Bailey hypothesised, where maybe it’s not the telomeres that are longer in space, but that cells with the longest telomeres are getting preferentially sampled somehow. “Maybe cells with longer telomeres are being localised because of chronic exposure to radiation or an injury response,” she says. “It’s not that telomeres got longer, it’s just that we're looking at a different population of cells that inherently have longer life.”
The nature of the study is unusual not just for its long duration and small sample size, but also for digging so deeply into the genetic makeup of the Kelly brothers. “Not only did we have to consider ourselves, we have to consider our children because some of the genetic traits are passed down,” says Kelly. “My brother and I decided to be pretty open because of the scientific knowledge and what we can learn from it. We figured that outweighed any kind of potential risk. We might be wrong. It is what it is.”
“It's been very difficult for us to do genetic work in the astronauts,” says Platts. This is partly due to the ethical and privacy considerations, but it also comes down to available tools and training. This was the first major long-term study to collect such a wide variety of data. “With this study, we got to do genetic analysis. We got to do immune studies. We got to do biochemistry. We got to do cognition all at the same time” says Platts.
Collecting the array of information was essential for outlining how the different data points reinforce each other to create a better understanding of the stresses of being in space and how resilient the human body is to those stresses, he explained. “It really laid the groundwork for our future work.” Bailey says because it was such a comprehensive view it gives scientists an idea of the questions they need to ask going forwards.
“We saw the body responding to stress that all the different levels,” says Platts. “Now we can go in and investigate in a more integrative way what exactly might be going on and what exactly that might mean for our crew members in the future.”
But comprehensive data collection is just part of the puzzle. When it comes down to it, this was just one person – or two, if including the terrestrial twin acting as an experimental control – and just one year. “An individual sample size is not statistically significant scientifically,” says Kelly, “but it is interesting anecdotal information where you can find out things that you didn't otherwise know and investigate further.”
“When you are only studying a very small number, it's very easy for there to be errors that pop up in the data,” explains Platts. But that’s the nature of research on astronauts. “We always have a low number of subjects when we're doing our research,” he says, which results in very careful procedures of pre- and post-mission testing for baselines and recovery, and conducting longer-duration research.
If Nasa is serious about its plans to send humans to the Moon, or even further to Mars, this research and more like it is essential. “We need to know what's going to happen to our crew members there and back,” says Platts. “We're finally getting into duration closer to what we might have for exploration. It's easy to assume that if you are in space for one month, then everything that happens that one month will be doubled at two months. But that's not necessarily the case.” Instead, the full-year study started hinting at where the impact of spaceflight on humans is non-linear: where impacts accelerate over time, or level out after reaching a plateau.
“We are explorers,” Platts says on the value of human spaceflight. “We need to move forward. We need to do other things. We need to expand science.”
This article was originally published by WIRED UK
