Space Anemia Could Limit Long-Duration Space Missions

Space travel increases red blood cell destruction, according to a study published today in Nature Medicine. An analysis of 14 astronauts showed their bodies destroyed 54 percent more red blood cells in space than they normally would on Earth.

“Space anemia has consistently been reported when astronauts returned to Earth since the first space missions, but we didn’t know why,” said the study’s lead author Guy Trudel from The Ottawa Hospital. “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 this 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. Astronauts lose 10 percent of the liquid in their blood vessels this way. It was thought astronauts rapidly destroyed 10 percent of their red blood cells to restore the balance, and that red blood cell control was back to normal after 10 days in space.

Instead, Dr. Trudel’s team 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.

On Earth, our bodies create and destroy 2 million red blood cells every second. The researchers found that astronauts were destroying 54 percent more red blood cells during the six months they were in space, or 3 million every second. These results were the same for both female and male astronauts.

While the team didn’t measure red blood cell production directly, they assume the astronauts generated extra red blood cells to compensate for the cells they destroyed. Otherwise, the astronauts would end up with severe anemia, and would have had major health problems in space. In this 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.