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For the first time, a global study has revealed how space travel can cause a decrease in the number of red blood cells, known as space anemia. The analysis of 14 astronauts showed that their bodies destroyed 54% more red blood cells in the period than they normally would on Earth.
“We’ve known for a long time that space anemia occurs when astronauts return from their mission, but we didn’t know why,” said lead author Guy Trudel, a rehabilitation physician and researcher at the
Hospital de Ottawa and professor of
University of Ottawa.
“Our study shows that upon arrival in space, more red blood cells are destroyed, and this continues throughout the duration of the astronaut’s mission,” explains the author of the work published in ”
Nature Medicine».
Prior to this study, space anemia was thought to be a rapid adaptation to fluids moving into the astronaut’s upper body when they first arrived in space. Astronauts lose 10% of the fluid in their blood vessels.
astronauts were thought to rapidly destroy 10% of your red blood cells to restore balance, and that red blood cell control returns to normal following 10 days in space.
Instead, Trudel’s team found that red blood cell destruction was a primary effect of being in space, not just caused by fluid changes. They demonstrated this by directly measuring red blood cell destruction in 14 astronauts during their six-month space missions.
On Earth, our bodies create and destroy 2 million red blood cells every second.
The researchers found that the astronauts were destroying a 54% more red blood cells during the six months they were in space, or 3 million per second. These results were the same for male and female astronauts.
Trudel’s team made this discovery thanks to techniques and methods they developed to accurately measure red blood cell destruction.
These methods were adapted to collect samples on board the
International Space Station. In the laboratory of the Trudel in the
University of Ottawa were able to accurately measure the small amounts of carbon monoxide in astronaut breath samples. One molecule of carbon monoxide is produced each time a molecule of heme, the deep red pigment in red blood cells, is destroyed.
Although the team did not measure red blood cell production directly, they assume that astronauts they made extra red blood cells to make up for the cells they destroyed. Otherwise, astronauts would end up with severe anemia and significant health problems in space.
“Fortunately, having fewer red blood cells in space is not a problem when your body is weightlessTrudel said. “But when landing on Earth and potentially other planets or moons, anemia that affects your energy, stamina and strength can threaten mission goals. The effects of anemia are only felt once you land and you have to deal with gravity once more.”
In this study, five of the 13 astronauts were clinically anemic when they landed; one of the 14 astronauts did not have blood drawn upon landing.
The researchers found that anemia related to space was reversible, and red blood cell levels progressively returned to normal three to four months following returning to Earth.
Interestingly, the team repeated the same measurements a year following the astronauts returned to Earth and found that red blood cell destruction was still 30% above pre-flight levels. These results suggest that structural changes may have occurred in the astronaut while in space that changed red blood cell control for up to a year following long-duration space missions.
The finding that space travel increases red blood cell destruction has several implications.
First, it supports screening astronauts or space tourists for existing blood or health conditions that are affected by anemia.
Second, a recent study by Trudel’s team found that the longer the space mission, the worse the anemia, which might affect long missions to the Moon and Mars.
In addition, the increased production of red blood cells will require a diet tailored for astronauts. And finally, it’s not clear how long the body can sustain this increased rate of red blood cell destruction and production.
These findings might also apply to life on Earth. As a rehab doctor, most of Trudel’s patients are anemic following being very ill for a long time with limited mobility, and the anemia hampers his ability to exercise and recover. Bed rest has been shown to cause anemia, but how it does so is unknown.
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