Some experts had argued that space anemia was just a short-term phenomenon due to changes in the fluids in our bodies under microgravity. It had even been commented that it was a myth. However, a new study points to a more destructive and long-lasting mechanism. Although the causes are not yet known, we can now say that we know a little more.
During a six-month space mission flight, researchers found that the human body destroys around 54% more red blood cells than it normally would on Earth. The data comes directly from the blood and breath of 14 astronauts on the International Space Station (ISS).
“This is the best description we have of red blood cell control in space and back on Earth,” says Guy Trudel, an epidemiologist at the University of Ottawa, Canada. “These findings are spectacular, considering that these measurements had not been done before and we had no idea if we were going to find anything. We were surprised and rewarded for our curiosity.”
Measurements were made through iron blood tests and carbon monoxide breath tests. For every molecule of carbon monoxide exhaled, one molecule of pigment found in red blood cells is also destroyed, making this a useful approximation of red blood cell loss.
Measurements were taken on Earth before departure and it was determined that they were losing around 2 million red blood cells per second . But during their time in orbit their bodies were destroying approximately 3 million blood cells per second .
In microgravity, the human body loses about 10% of the fluid that flows through the blood vessels, as blood pools in the head and chest. This is why astronauts sometimes appear bloated in videos from the ISS. This fact was, for years, the explanation of space anemia: the loss of red blood cells could be the way in which our body compensated for the loss of blood volume. But this idea is what has been denied by this pioneering study.
The loss of red blood cells does not compensate for the composition of our blood, but continues beyond space travel. Even after 120 days later, when all the red blood cells in the astronaut’s body had been created in space, red blood cell loss continued at a similar rate.
“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,” says Trudel.
The study reveals that five of thirteen astronauts (one did not have blood drawn upon landing) were clinically anemic upon return to Earth. Despite this, they found that this anemia was reversible and that the levels of red blood cells progressively returned to normal between three and four months after returning to Earth. But the team repeated the measurements a year after the astronauts arrived on Earth and found that red blood cell destruction was still 30% higher than pre-flight levels. This fact suggests that astronauts underwent structural changes in space that modified the control of red blood cells in the case of long-duration space missions.
The study did not measure red blood cell production, since no astronauts suffered from severe anemia, despite significant red blood cell losses, so it follows that the bodies may also have been producing more red blood cells than normal while in space. space.
“Fortunately, having fewer red blood cells in space isn’t a problem when your body is weightless,” Trudel says. But when landing on Earth and potentially other planets or moons, anemia that affects energy, stamina, and strength can jeopardize mission goals. The effects of anemia show up when you go back to gravity again.”
If red blood cell production compensation is confirmed, astronauts’ diets will need to be adjusted accordingly. In addition, an increase in red blood cell production can put additional pressure on bone marrow function, requiring increased energy consumption. On the other hand, if astronauts are not properly protected, they could be at risk of damage to their heart, lungs, bones, brain, and muscular systems when they return to Earth.
“These findings suggest that the destruction of red blood cells, termed hemolysis, is a major effect of microgravity in spaceflight and support the hypothesis that spaceflight-associated anemia is a hemolytic condition that should be considered in space flight. detection and tracking of both astronauts and space tourists”.
On the official website of the Ottawa Hospital Research Institute, a story has already appeared about this study led by Guy Trudel and which is called MEDULA, due to its relationship with research on how long-term space travel affects the bone marrow. duration. That publication discussed the case of Dr. David Saint-Jacques, an astronaut from the Canadian Space Agency (CSA)
“On board the International Space Station, I will participate in hundreds of scientific experiments on behalf of researchers from all over the world”, said Dr. Saint-Jacques at the time. “I will run Canadian experiments that focus on health sciences, like MARROW. As a doctor, I have a great interest in that type of research that has concrete impacts on the lives of Canadians.”
Saint-Jacques was one of 14 astronauts who enrolled in Trudel’s study and thanks to which we have taken a new step in preparing humans for long-duration space travel.
“What astronauts experience in space is similar to what I see in my own patients,” explained Dr. Trudel, a researcher and rehabilitation physician at the Ottawa Hospital Rehabilitation Center and a professor at the University of Ottawa. “Low gravity in space weakens muscles and bones. The same thing happens with patients who spend a lot of time in bed in the intensive care unit.”
Adapted from Study: Being in space destroys more red blood cells , University of Ottawa. The article Hemolysis contributes to anemia during long-duration space flight has been published in Nature on January 14, 2022 and is signed by Guy Trudel, Nibras Shahin, Timothy Ramsay, Odette Laneuville and Hakim Louati.
