Being in space destroys more red blood cells

January 14, 2022

(Nanwerk NewsA study, the first of its kind in the world, has revealed how space travel can cause the number of red blood cells to drop, known as space anemia. An analysis of 14 astronauts showed that their bodies destroyed 54 percent more red blood cells in space than they normally do on Earth, according to a study published in nature medicine (“Hemolysis contributes to anemia during long-duration spaceflight”).

Lead author Dr. Jay Trudel, MD, a rehabilitation physician and researcher at The Ottawa Hospital and Professor at the University of Ottawa, said. “Our study shows that upon reaching space, more red blood cells are destroyed, and this continues for the duration of the astronaut’s mission.” Astronaut David Saint-Jacques collects breath, ambient air, and blood samples for the MARROWتجربة Experiment Astronaut David Saint-Jacques collects breath, ambient air, and blood samples for the MARROW Experiment. (Image: NASA)

Prior to this study, space anemia was thought to be a rapid adaptation to fluids that travel to the upper body of an astronaut when they first reach space. Astronauts lose 10 percent of the fluid in their blood vessels in this way. It was thought that astronauts quickly destroyed 10 percent of their red blood cells to restore homeostasis, and red blood cell control returned to normal after 10 days in space.

Instead, Dr. Trudel’s team found that the destruction of red blood cells was a primary consequence of being in space, and not just because of 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 two million red blood cells every second. The researchers found that astronauts were destroying 54 percent of their red blood cells during the six months they spent in space, or 3 million every second. These results were the same for both female and male astronauts.

Dr. Trudel’s team made the discovery thanks to the techniques and methods they developed to accurately measure red blood cell destruction. These methods were then adapted for sample collection aboard the International Space Station. In Dr. Trudel’s lab at the University of Ottawa, they were able to accurately measure trace amounts of carbon monoxide in breath samples taken from astronauts. One molecule of carbon monoxide is produced each time one molecule of heme, the deep red pigment in red blood cells, is destroyed.

While the team didn’t directly measure red blood cell production, they hypothesize that the astronauts generated extra red blood cells to compensate for the ones they destroyed. Otherwise, the astronauts would end up severely anemic, and have major health problems in space.

“Fortunately, having fewer red blood cells in space is not a problem when your body is weightless,” Dr. Trudel said. “But when landing on Earth and possibly on other planets or moons, anemia affecting your energy, endurance, and strength can threaten mission goals. You don’t feel the effects of anemia until after you land, and you have to deal with gravity again.”

In this study, five of the 13 astronauts were clinically anemic when they landed—not one of the 14 astronauts had blood drawn upon landing. The researchers saw that space-related anemia was reversible, with red blood cell levels gradually returning to normal three to four months after returning to Earth.

Interestingly, the team repeated the same measurements one year after the astronauts returned to Earth, finding that red blood cell destruction was still 30 percent higher than preflight levels. These findings suggest that structural changes may have occurred to the astronaut while in space that altered red blood cell control for up to a year after long-duration space missions.

The discovery that space travel increases red blood cell destruction has several implications. First, it supports screening astronauts or space tourists for blood or existing health conditions that are affected by anemia. Second, a recent study by Dr. Trudel’s team found that the longer a space mission took, the worse the anemia could get, which could affect longer flights to the Moon and Mars. Third, the increased production of red blood cells requires an adequate diet for the astronauts. Finally, it is not clear how long the body can maintain this high rate of destruction and production of red blood cells.

These findings can also be applied to life on Earth. As a rehabilitation physician, most Dr. Trudel’s patients develop anemia after being ill for a long time with limited mobility, and anemia hampers their ability to exercise and recover. Bed rest has been shown to cause anemia, but how this occurs is not known. Dr. Trudel thinks the mechanism may be like anemia in space. His team will investigate this hypothesis during future bed rest studies on Earth.

“If we can figure out exactly what is causing this anemia, there is potential to treat or prevent it, both for astronauts and for patients here on Earth,” Dr. Trudel said.

These are the first published results from MARROW, a trial made in Ottawa that looks at bone marrow health and blood production in space. The project is funded by the Canadian Space Agency and led by Dr. Trudel.

“This is the best description we have of controlling red blood cells in space and after returning to Earth,” said Dr. Trudel. “These results are amazing, given that these measurements had never been done before and we had no idea if we would find anything. We were surprised and rewarded for our curiosity.”

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