When pediatric cancer survivor Hayley Arceneaux and three crewmates spent three days in space in 2021 as part of SpaceX's Inspiration4 mission, they made history as the first all-civilian team to orbit Earth. They also provided the most in-depth data on record regarding the effects of space travel on the human body.

New research based on these data details changes in the brain, heart, muscles, kidneys, and skin, as well as immune regulation, stress levels, and the activity of subcellular structures called mitochondria in the microgravity environment, increased radiation, and other factors in space.

More than 95% of the biomarkers tracked in the research returned to preflight levels in the months after the crew returned to Earth, although some abnormalities, including in the mitochondria, persisted. However, the data indicated that short-duration spaceflights do not pose significant health risks.

"We did not see anything that was worrisome, thankfully," said Chris Mason, PhD, a professor of physiology and biophysics at Weill Cornell Medicine, who helped lead the research. Studies were published on Tuesday in Nature and other journals. "This bodes well for other groups of civilians planning to live and work in space."

"We did see some evidence of brain-associated proteins in the blood after the mission, which we had also seen once before in the Twins Study (a 2019 study based on retired NASA astronauts and twins Scott and Mark Kelly), and we think is evidence of brain stress during the mission," Mason added.

Mason said this might be explained by findings in experimental mice flown to space that experienced disruptions in the blood-brain barrier, a layer of cells protecting the brain. Cognitive function in the Inspiration4 crew, as measured by Mathias Basner, MD, University of Pennsylvania, was not affected, Mason noted.

Arceneaux, a physician assistant at St. Jude Children's Research Hospital in Memphis and the mission's medical officer, and her crewmates—aerospace data engineer Chris Sembroski, geoscientist Sian Proctor, PhD, and billionaire entrepreneur Jared Isaacman—were monitored before, during, and after the flight. They underwent extensive testing and provided blood, saliva, and other samples, including skin biopsies.

"I love my space scar," said Arceneaux, who was 29 at the time and became the youngest American to orbit Earth, adding that the crew "really wanted to make a scientific impact."

The research included data from the two women and two men from Inspiration4, as well as information from 64 astronauts who participated in longer stints aboard the International Space Station (ISS) and other missions. Inspiration4 flew at roughly 370 miles (590 km) above Earth, higher than the ISS, meaning the crew faced higher radiation levels.

"So far, females seem to return to baseline (preflight status) faster than males, but our numbers are too small for this to be definitive," Mason said.

The onset of a "second Space Age," characterized by commercial missions, has heightened the urgency to understand health risks, according to bioinformatician Afshin Beheshti, PhD, of the Blue Marble Space Institute of Science in Seattle, another leader of the research.

The amount of time spent in space is considered a key factor in the health effects, with greater concern over long-duration missions.

"The longer the duration in space, the greater the increase in health risks observed," Beheshti said.

Beheshti said data from Inspiration4 and Japan's space agency, along with Earth-based experiments, detailed the significant impact of spaceflight on mitochondrial function and immune regulation.

"Previous publications have touched on these issues, but the new findings indicate that microgravity and space radiation systematically affect the body, leading to dysfunction at the cellular level that impacts multiple organs, including muscles, kidneys, heart, skin, and CNS-related (central nervous system) tissues," Beheshti said.

"The systemic response observed in spaceflight has been shown to contribute to increased frailty in humans. Space is known to accelerate aging and many human diseases, and the research underscores this by identifying key health risks that can be targeted for countermeasures," Beheshti added.

The research pointed to potential paths to mitigate damage caused by space radiation. It found that certain molecules involved in regulating gene activity were inhibited in space.

"This research demonstrates that targeting these key factors can rescue the immune and inflammatory pathways dysregulated in space," Beheshti said.

The researchers are taking a forward-looking approach.

"If humans are going to be living and working in space, or living on the moon and Mars, we need to set a baseline data of metrics for how the body responds to space," Mason said.