After nearly 65 years of human spaceflight, we are still finding out just how dangerous it is for the human body to travel to space. Sure, we all know about the need for pressurized suits and breathable air for astronauts. We’ve read about a growing body (excuse the pun) of knowledge about how low-gravity environments and weightlessness affect astronauts. Specifically, there are effects on their hearts, eyes, and bones. And, of course, we know about the dangers of simply lifting off from the planet (or returning to it after a mission). All those are unforgettable challenges. They must be solved if humans are to spend long periods of time traveling to other planets or building space installations. But, did we ever think about what happens to our blood in space?
It turns out there’s one more danger to add to the list: the risk of developing space anemia. It turns out that traveling in space for long periods of time destroys red blood cells in an astronaut’s body. This space anemia isn’t a new problem—space medicos have known about it for a long time. What they needed to do was nail down the specifics of when the anemia started. That meant studying several astronauts from the time they arrived in space to the time they came home. That way, doctors could figure out what happened to the red blood cells at different times in a mission.
The leading researcher, Dr. Guy Trudel, who works at Ottawa Hospital and teaches at the University of Ottawa, put together a team that devised a series of techniques to find out how much being in space affected astronaut blood cells. They did this by measuring red blood cell destruction in 14 astronauts who each spent six months onboard the ISS.
Changes in Blood in Space
People generally tend to generate and destroy about two million red blood cells each second. This is entirely normal and part of the way we live here on Earth. In space, those numbers change quite a bit. It turns out that astronaut bodies destroy 54 percent more red blood cells during their time in space than they do here on Earth. That’s true for all astronauts and the same whether they are male or female.
Now, the high loss of blood cells didn’t affect the health of the astronauts, and the team assumed that the astronauts more than made up for the red blood cell loss by generating extra ones during their time in space. Still, several of the astronauts turned out to be clinically anemic when they landed back on terra firma. The good news is that anemia reversed itself over the course of three or four months after the astronauts were safely back on Earth. Interestingly, the team measured astronauts again one year after their missions and found that red blood cell destruction was still 30 percent above preflight levels. It turns out that structural changes may have happened to the astronaut while they were in space that changed red blood cell control for up to a year after long-duration space missions.
The Implications in Space and on Earth
This discovery has some interesting implications for future missions—as well as for anemia patients here on Earth. For space travelers, if anemia is going to be a constant threat, then agencies will need to take some action. Obviously, some pretty strict screening of astronauts or space tourists for existing blood or health conditions is necessary. Second, it turns out that the longer the space mission, the worse the anemia gets. That presents some pretty big challenges for long-duration missions to the Moon and Mars.
Those trips will not be quick jaunts—they could be months or years long. So, the threat of anemia could very well affect the mission. Third, this tendency toward increased red blood cell production will change the kinds of diets astronauts eat while on mission. Finally, it’s unclear how long a space traveler can maintain an accelerated rate of destruction and production of red blood cells.
On Earth, patients with blood disorders are often anemic after being very ill for a long time; and limited mobility during illness is a factor. To get even more specific, anemia hinders a person’s ability to exercise and recover. Bedrest has been shown to cause anemia, but how it does this is unknown. However, the mechanism behind this Earth-based effect on red blood cells may be quite similar to the one that causes space anemia. If that’s true, blood doctors may have a new avenue of study to figure out what’s causing a person’s anemia. If the mechanism is the same on both Earth and in space, that’s a breakthrough. It means they can figure out ways to treat it—and maybe even prevent it.
If you want to know more about the study, there’s a paper published in the journal Nature Medicine that gives details.