On Earth, our bodies create and destroy 2 million red blood cells every second. In a new study published today in the journal Nature Medicine, a team of scientists from the Ottawa Hospital Research Institute and the University of Ottawa found that astronauts were destroying 54% more red blood cells during their 6-month missions onboard the International Space Station, or 3 million every second.
Trudel et al. suggest that the destruction of red blood cells, termed hemolysis, is a primary effect of microgravity in space flight and support the hypothesis that the anemia associated with space flight is a hemolytic condition that should be considered in the screening and monitoring of both astronauts and space tourists. Image credit: NASA.
“Space anemia has consistently been reported when astronauts returned to Earth since the first space missions, but we didn’t know why,” said Professor Guy Trudel, a rehabilitation physician and researcher at the Ottawa Hospital Research Institute and the University of Ottawa.
“Our study shows that upon arriving in space, more red blood cells are destroyed, and this continues for the entire duration of the astronaut’s mission.”
Before the new study, space anemia was thought to be a quick adaptation to fluids shifting into the astronaut’s upper body when they first arrived in space.
Instead, the authors found that the red blood cell destruction was a primary effect of being in space, not just caused by fluid shifts.
They demonstrated this by directly measuring red blood cell destruction in 14 astronauts during their six-month space missions.
“Thankfully, having fewer red blood cells in space isn’t a problem when your body is weightless,” Professor Trudel said.
“But when landing on Earth and potentially on other planets or moons, anemia affecting your energy, endurance, and strength can threaten mission objectives.”
“The effects of anemia are only felt once you land, and must deal with gravity again.”
In the study, five out of 13 astronauts were clinically anemic when they landed — one of the 14 astronauts did not have blood drawn on landing.
The researchers saw that space-related anemia was reversible, with red blood cells levels progressively returning to normal three to four months after returning to Earth.
Interestingly, they repeated the same measurements one year after astronauts returned to Earth, and found that red blood cell destruction was still 30% above preflight levels.
These results suggest 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 discovery has several implications:
(i) it supports screening astronauts or space tourists for existing blood or health conditions that are affected by anemia;
(ii) the longer the space mission, the worse the anemia, which could impact long missions to the Moon and Mars;
(iii) increased red blood cell production will require an adapted diet for astronauts;
(iv) it’s unclear how long the body can maintain this higher rate of destruction and production of red blood cells.
According to the scientists, their findings could also be applied to life on Earth.
“If we can find out exactly what’s causing this anemia, then there is a potential to treat it or prevent it, both for astronauts and for patients here on Earth,” Professor Trudel said.
G. Trudel et al. Hemolysis contributes to anemia during long-duration space flight. Nat Med, published online January 14, 2022; doi: 10.1038/s41591-021-01637-7