Wed. Jan 26th, 2022

When we are on Earth, our bodies create and destroy 2 million of these cells per second. In space, astronauts experienced 3 million red blood cells destroyed per second, resulting in a loss of 54% more cells than humans on Earth experience, according to a new study.

Lower red blood cell counts in astronauts are known as rumanemia.

“Rumanemia has been consistently reported since astronauts returned to Earth since the first space missions, but we did not know why,” said study author Dr. Guy Trudel, a rehabilitation physician and researcher at Ottawa Hospital and professor at the University of Ottawa, in a statement.

Scientists took breath and blood samples from 14 astronauts before their six-month stay on the International Space Station. The astronauts also took samples four times during their flights. The scientists also collected blood from the astronauts up to a year after their space flight.

The 11 men’s and three women’s flights took place between 2015 and 2020. The results were published Friday in the journal Nature Medicine.

A surprising find

When astronauts are in space, they experience a shift of body fluids towards the upper body due to the lack of gravity. This results in increased pressure on the brain and eyes, causing cardiovascular problems and a loss of 10% of the fluid in their blood vessels.

A special sleeping bag could help astronauts with vision problems in space

Researchers believed that rumanemia was the body’s way of adapting to fluid exchange, which resulted in the destruction of red blood cells to restore balance. They also believed that the loss of red blood cells was only temporary and recovered themselves after the astronauts had adapted after spending 10 days in space.

Trudel and his team discovered a surprising result – the space environment is the real culprit.

“Our investigation shows that upon arrival in space, several red blood cells are destroyed, and this continues throughout the duration of the astronaut’s mission,” he said.

The European Space Agency's astronaut Tim Peake is shown after his first blood test was conducted in space.

The research team developed ways to measure the destruction of red blood cells, including measuring the amount of carbon monoxide found in breath samples from astronauts. Each time a molecule heme, or the red signature pigment in red blood cells, is destroyed, it forms a molecule of carbon monoxide.

The team was not able to directly measure the production of red blood cells in the astronauts, but they expect the astronauts to experience the generation of extra red blood cells in response to increased destruction. If this had not happened, all the astronauts would have suffered the effects and health problems associated with severe anemia while in space.

“Fortunately, having fewer red blood cells in space when your body is weightless is not a problem,” Trudel said. “But when you land on Earth and potentially on other planets or moons, anemia that affects your energy, endurance and strength can threaten the mission’s goals. The effects of anemia are only felt when you land, and must deal with gravity again.”

Long-term effects

After returning to Earth, five out of 13 astronauts were diagnosed as clinically anemic. One of the astronauts did not get blood taken after landing.

Treatment of the first known blood clot in space

Follow-up samples taken from the astronauts showed that rumanemia is reversible because their red blood cells gradually returned to normal between three to four months after their return.

Samples collected a year after the astronauts landed on Earth, however, showed that the rate of destruction of red blood cells was still increasing, about 30% above what they experienced before their space flight.

The researchers believe this suggests that prolonged space missions may result in structural changes affecting red blood cells.

The results are the first results published by MARROW, an experiment that examines bone marrow health and blood production when astronauts are in space.
NASA astronaut Anne McClain is shown with biomedical equipment for MARROW on the International Space Station.
The results highlight the importance of screening both astronauts and space tourists for health conditions that may be affected by anemia, and monitoring for any problems during missions. An earlier study by Trudel and his team also revealed that longer space missions exacerbate anemia.

For now, it is uncertain how long the human body can support an increased rate of both destruction and production of red blood cells.

To combat this risk, the researchers suggest that astronauts’ diets be changed to support better blood health.

The experience from this research could also be applied to anemia patients on Earth, especially those who experience it after illness and prolonged bed rest. While the direct cause of this type of anemia is unknown, it may be similar to what is happening in the room.

“If we can find out exactly what causes this anemia, then there is a potential to treat it or prevent it, both for astronauts and for patients here on Earth,” Trudel said. “This is the best description we have of controlling red blood cells in space and after returning to Earth. We were surprised and rewarded for our curiosity.”

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