Even short space trips can change astronaut’s biology

Others SciTech Even short space trips can change astronaut’s biology New studies offer a comprehensive look at the spaceflight health, explains Susan Bailey of Colorado State University

Only about 600 people have ever travelled to space. The vast majority of astronauts over the past six decades have been middle-aged men on short-duration missions of fewer than 20 days.

Today, with private, commercial and multinational spaceflight providers and flyers entering the market, we are witnessing a new era of human spaceflight. Missions have ranged from minutes, hours and days to months.

As humanity looks ahead to returning to the Moon over the coming decade, space exploration missions will be much longer, with many more space travellers and even space tourists. This also means that a wider diversity of people will experience the extreme environment of space - more women and people of different ethnicities, ages and health status.

Since people respond differently to the unique stressors and exposures of space, researchers in space health, like me, seek to better understand the human health effects of spaceflight. With such information, we can figure out how to help astronauts stay healthy both while they’re in space and once they return to Earth.

As part of the historic NASA Twins Study, in 2019, my colleagues and I published groundbreaking research on how one year on board the International Space Station affects the human body.

I am a radiation cancer biologist in Colorado State University’s Department of Environmental and Radiological Health Sciences. I’ve spent past few years continuing to build on that earlier research in a series of papers recently published across the portfolio of Nature

journals. These papers are part of the Space Omics and Medical Atlas package of manuscripts, data, protocols and repositories that represent the largest collection ever assembled for aerospace medicine and space biology. Over 100 institutions from 25 countries contributed to the coordinated release of a wide range of spaceflight data.

The NASA Twins Study

NASA’s Twins Study seized on a unique research opportunity.

NASA selected astronaut Scott Kelly for the agency’s first one-year mission, during which he spent a year on board the International Space Station from 2015 into 2016. Over the same time period, his identical twin brother, Mark Kelly, a former astronaut and current US senator representing Arizona, remained on Earth. My team and I examined blood samples collected from the twin in space and his genetically matched twin back on Earth before, during and after spaceflight. We found that Scott’s telomeres - the protective caps at the ends of chromosomes, much like the plastic tip that keeps a shoelace from fraying - lengthened, quite unexpectedly, during his year in space.

When Scott returned to Earth, however, his telomeres quickly shortened. Over the months, his telomeres recovered but were still shorter after his journey than they had been before he went to space.

As you get older, your telomeres shorten because of a variety of factors, including stress. The length of your telomeres can serve as a biological indicator of your risk for developing age-related conditions such as dementia, cardiovascular disease and cancer.

In a separate study, my team studied a cohort of 10 astronauts on six-month missions on board the International Space Station. We also had a control group of age- and sex-matched participants who stayed on the ground.

We measured telomere length before, during and after spaceflight and again found that telomeres were longer during spaceflight and then shortened upon return to Earth. Overall, the astronauts had many more short telomeres after spaceflight than they had before.

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One of the other Twins Study investigators, Christopher Mason, and I conducted another telomere study - this time with twin high-altitude mountain climbers - a somewhat similar extreme environment on Earth.