Space anemia: Astronauts lose red blood cells for the duration of their time in space

A University of Ottawa-led study of anemia in astronauts not only led to new discoveries, but could provide insight on anemia in people on bed rest, the researchers say. The study found that red blood cell loss persists for the duration of an astronaut’s stay in space, and is not just a temporary reaction to change in gravity. “What we found was a surprise,” Dr. Guy Trudel, a rehabilitation physician and professor of medicine at the University of Ottawa, told The Ottawa Citizen. Previously, anemia in astronauts was thought to be short-lived, and that the drop in red blood cell count was an acute adaption to other bodily shifts happening in microgravity, such as more blood going to the head and chest. The thinking was that the loss of red blood cells would cease after ten days in space. The finding that red blood cell destruction (hemolysis) continued for the duration of spaceflight could impact future space exploration. Any mission to Mars will require more than two years in space. How long humans can maintain red blood cell production to compensate for high red blood cell loss is not yet understood, Dr. Trudel said. “How long can that hypermetabolism continue? We don’t know that. That’s a knowledge gap,” Dr. Trudel said. Read: Down to Earth: Canadian astronaut MD returns to practice during pandemic The study involved 14 astronauts who flew International Space Station (ISS) missions that were four months or longer between 2015 and 2020. Each astronaut supplied breath and air samples throughout their time on the ISS. When a red blood cell dies, it releases carbon monoxide. Researchers used carbon monoxide levels in the breath samples to calculate the extent of hemolysis in each astronaut. The researchers also measured serum iron and transferrin and ferritin levels in the blood samples. The carbon monoxide elimination over six months in space was increased by 54% compared to pre-flight levels on earth, suggesting that red blood cell destruction was increased by 54% in space compared to on earth. Once the astronauts returned to earth, hemolysis decreased. “The pattern of hemolysis in the three phases of the study (on Earth, in space and back on Earth) confirmed that increased hemolysis was tightly linked to the space environment,” the researchers stated in their paper. A year after returning from space, the astronauts continued to show evidence of increased red blood cell loss. “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,” Dr. Trudel said. Dr. Trudel told BBC news that space anemia is similar to that experienced by patients who have been inactive in the ICU and may be caused by the same mechanism. The Canadian Space Agency announced on January 27, 2022 that it is supporting Dr. Trudel’s research on the effects of prolonged bedrest on anemia and hemolysis. As part of the study, volunteers stay in bed for several weeks. The paper was published in Nature Medicine on January 14 and is available through open access. Read: Physician included in NASA's newly selected astronauts

Space anemia: Astronauts lose red blood cells for the duration of their time in space

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