Extended space travel may impair astronauts’ immune systems: study

Tucson, AZ — Long-duration spaceflight may pose a major hazard to astronauts’ immune systems, a recent study shows.

Researchers from the University of Arizona examined how flights of six months or longer impact the function of natural killer cells – white blood cells that eliminate cancerous cells in the body while stunting the reactivation of old viruses. They analyzed blood samples of eight astronauts who completed missions to the International Space Station with those of eight healthy individuals who remained on Earth. The crew members’ blood samples were taken before launch, at various points during the mission and after returning from space.

Findings showed that the astronauts experienced impaired killer cell functions during spaceflight, compared with before and after the mission. After three months in space, killer cells performed about 50 percent less efficiently against external leukemia cells, the researchers said, with cell function appearing to decrease more prominently among first-time astronauts.

“When we look at the function of the astronaut samples during flight compared to their own samples before they flew, it goes down,” Richard Simpson, senior author and associate professor of nutritional sciences at UA, said in a Jan. 24 press release. “When we compare them to controls who stayed on Earth, it still goes down. I don’t think there’s any doubt that [killer cell] function is decreasing in the spaceflight environment when analyzed in a cell culture system.”

Simpson added that astronauts who complete long-duration missions may face an increased risk of cancer because of their prolonged exposure to radiation. Spacecraft traditionally are sterile environments, so the possible spread of existing viruses in a crew member’s body becomes a greater concern than developing a “community-type infection” such as the flu.

The study was published online Nov. 1 in the Journal of Applied Physiology.