As homesickness, muscle atrophy, bone thinning, a heightened risk of cancer, the inescapable companionship of super-powered beings and the prospect of death in the endless vacuum of space are not enough, male astronauts may develop erectile dysfunction upon returning from deep space, scientists say.
In what is said to be the first study to assess the impact of galactic radiation and weightlessness on men's sexual health, NASA-funded researchers have found that galactic cosmic rays, followed by microgravity, impair the function of erectile tissue, with effects that may last for decades.
U.S. researchers raised their concerns in a report on Wednesday, saying they had discovered "a new health risk that needs to be considered in deep space exploration." They call for close monitoring of the sexual health of astronauts upon return from future deep space missions, noting that certain antioxidants may help counteract adverse effects by blocking harmful biological processes.
"While the negative effects of galactic cosmic radiation are long-lasting, the functional improvements induced by acute targeting of redox and nitric oxide pathways in tissues suggest that erectile dysfunction may be treatable," said the study's senior author, Dr. Justin LaFavor, an expert in neurovascular dysfunction at Florida State University.
NASA and other major space agencies are preparing for long-term expeditions to the moon and ambitious missions to Mars. NASA's Artemis program hopes to send astronauts to the moon as early as next year, and preliminary plans for a manned mission to Mars are as early as 2040.
Since the dawn of the space age, scientists have been exploring the effects of weightlessness and cosmic radiation (high-energy particles, X-rays, and gamma rays from stars and other celestial bodies) on human physiology. The work has prompted several precautions, including special exercises aboard the International Space Station (ISS) to protect astronauts' bones and muscles from wear and tear.
But no one has studied the effects of spaceflight on erectile dysfunction, according to Rafael and colleagues at Wake Forest University School of Medicine in North Carolina. "While erectile dysfunction affects more than half of men over the age of 40 and is an important factor in life satisfaction, the impact of space travel on erectile function remains obscure," they write in the journal Faseb.
The Earth's magnetic field and atmosphere protect the Earth well from cosmic radiation, but there are no effective barriers on the Moon and Mars and in space between them. On the International Space Station, astronauts are protected by shielding and the Earth's magnetic field, but they still receive the same amount of radiation in a week as people on the ground receive in a year.
With no humans readily available, researchers have turned to mice to explore the effects of spaceflight on male physiology. In a series of experiments, dozens of rats were suspended in harnesses at a 30-degree angle and exposed to simulated galactic cosmic rays at NASA's Space Radiation Laboratory in New York.
A year later, analysis of rat tissue showed that even low levels of exposure to galactic cosmic rays increased oxidative stress in the animals. This impairs the function of the arteries that supply blood to the penis and erectile tissue. Weightlessness also has an effect, but it's not as noticeable.
"Taken together, these results suggest that neurovascular function of erectile tissue may be compromised during the sexual health of astronauts returning to Earth from long-duration deep space exploration," the authors wrote.
It's not all bad news for future astronauts. Using specific antioxidants appears to improve tissue function after exposure to galactic cosmic rays, suggesting male astronauts heading to Mars need not be too depressed.