Astronauts face health risks—even on short trips in space
https://web.archive.org/web/20240612013641if_/https://www.science.org/content/article/astronauts-face-health-risks-even-short-trips-space

In 2021, four passengers, including billionaire businessman Jared Isaacman, rode into space on a SpaceX rocket, orbiting Earth for 3 days in the company’s Dragon capsule before splashing down in the Atlantic Ocean. The trip, financed by Isaacman and called Inspiration4, was the first privately funded orbital mission on a private rocket carrying private citizens—setting the stage for more routine tourist space travel today.

The astronauts also underwent intensive medical monitoring before, during, and after their flight. Now, researchers have analyzed how the space radiation and weightlessness they experienced affected their bodies, releasing a package of more than 40 studies, most of them based on Inspiration4 data. Published today in Nature journals, the Space Omics and Medical Atlas (SOMA) includes studies of the participants’ genomes, microbiomes, transcriptomes (the messenger RNA made from their genes), and proteomes (their panoply of proteins).

“This is the biggest release of biomedical data from astronauts,” says Christopher Mason, a geneticist at Weill Cornell Medicine who led many of the new papers.

NASA and other space agencies have studied the health of hundreds of astronauts over the past 6 decades, finding a wide range of impacts, including elevated long-term cancer risks from exposure to space radiation, muscle atrophy and bone loss from life in microgravity, and changes in vision. But private spaceflights are giving researchers the chance to study the risks in more detail, with the latest biomedical technologies. “A good 30% to 40% of [the SOMA assays] are new,” Mason says.

One message from the SOMA studies, Mason says, is that the same health effects that professional astronauts experience over their long expeditions turn up among space tourists who only spend a few days in orbit.

The findings could also have implications for long-duration space exploration beyond the protective cocoon of Earth’s magnetic field, which deflects some space radiation. “We don’t yet fully understand all of the risks,” says Amy McGuire, a biomedical ethicist at Baylor College of Medicine. “This is also why it is so important that early space tourists participate in research.”

Mason and his colleagues focused their studies on roughly 20 astronauts for whom extensive data were collected: the four Inspiration4 passengers, recent astronauts from Japan’s space agency, and NASA astronauts Scott and Mark Kelly, twins who took part in an earlier study of space effects.

The group represents a broader range of people than in past studies—not just healthy, fit, and relatively young NASA astronauts, says J. D. Polk, NASA’s chief health and medical officer. “Private companies are flying a wider breadth of the population, so it’s helpful for them to do research,” he says.

Moreover, the Inspiration4 crew orbited Earth at 585 kilometers above the ground, a significantly higher altitude than the International Space Station (ISS) and China’s Tiangong station, subjecting the passengers to a different, and likely more intense, space radiation environment.

One study confirms NASA’s research on the Kelly twins, showing how space stressed the Inspiration4 crew’s immune cells, affecting the chromatin, or chromosome material, in a type of white blood cell called monocytes. Mason says the immune system is “on high alert, aggravated.” The researchers also sequenced RNA in astronauts’ blood, finding that the stress of spaceflight affected the transcription of immune system genes, possibly reducing the body’s ability to defend against viruses.

In another hint of trouble, the team documented a peculiar lengthening of passengers’ telomeres, caps that protect chromosomes and prevent them from fraying. Aging shrinks telomeres, but longer than normal telomeres aren’t healthy either, as they’re associated with higher cancer risks.

The team did explore a possible way to prevent some of the radiation damage: by suppressing the function of microRNAs—short RNA molecules that can silence genes and are considered to be markers of space radiation damage. The researchers developed inhibitors of microRNA, called antagomirs, and applied them to cell cultures derived from blood samples from the Inspiration4 crew and Japanese astronauts. The treated cells suffered less radiation damage than control samples. The scientists are still far from developing a therapeutic, however.

The studies suggest men and women face different risks in space and recover at different rates after returning to Earth, says Tejaswini Mishra, a geneticist at Stanford University who previously worked on NASA’s twins study.

Women’s vision appears to be less affected by microgravity, and their monocytes returned to normal more quickly than men’s. But women space travelers appear to be more vulnerable to some cardiovascular and cancer risks. There’s still not much data available for women astronauts, though, Mishra says, and those sex differences need further study.

As commercial spaceflight becomes more common, researchers will need to develop an ethical framework that balances the research’s potential benefits with the passengers’ privacy concerns and the risks of performing research on them, says McGuire, lead author of a Science policy forum on the subject. “There should be an expectation of everyone who travels to space to participate at least in minimal risk research,” McGuire says. “That is, to have biomarker, biometric, biomedical data collected about them, before, during, and after they take these trips.”

Mason and his colleagues are making all of the SOMA data available in a comprehensive astronaut “biobank” for other researchers to study, in the Weill Cornell Medicine’s CAMbank.

They are also expanding their studies, examining data from private astronauts who traveled to the ISS on two flights brokered by the company Axiom. They’re planning to analyze data from additional Axiom flights this year and from Polaris Dawn, a flight that will take Isaacman back to space this summer with a new crew and will include the first spacewalk for paying customers.

Access to space is expanding as companies ramp up plans for space tourism, commercial space stations, and even private trips to the Moon. The need to understand the health risks is growing—but so is the opportunity for research. “Soon we’ll have more data from multiple missions and multiple crews,” Mason says. “I’m optimistic about the future.”