Astronauts destroy 54 per cent more red blood cells during space travel than on Earth, according to a new Ottawa study that holds important implications for both rehab medicine and future Mars missions.
Published in the journal Nature Medicine, the study followed 14 astronauts and found they all suffered “space anemia” throughout six-month missions to the International Space Station.
Previously, it was believed that space anemia was a temporary condition and that astronauts’ bodies adjusted to it after a few weeks in microgravity.
But the Ottawa-led study discovered the phenomenon is sustained throughout the full duration of an astronaut’s space travel.
Researchers found astronauts were destroying three million red blood cells every second while in space: 54 per cent more than on Earth. Results were the same for the 11 male and three female astronauts in the study.
“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,” said the study’s lead author, Dr. Guy Trudel, a rehab physician and researcher at The Ottawa Hospital.
NASA says a human mission to Mars would require astronauts to endure the rigours of space travel for two years or more.
Trudel says researchers need to understand how long the human body can maintain the high rate of red blood cell production needed to offset the rapid destruction of those cells in space.
“How long can that hypermetabolism continue? We don’t know that. That’s a knowledge gap,” said Trudel, a University of Ottawa professor.
Space anemia is not a problem when astronauts are weightless, he said, but, as soon as they land on Earth, Mars or the Moon, it can affect their energy, endurance and strength levels. “The effects of anemia are only felt once you land and must deal with gravity again,” Trudel said.
On Earth, those with clinical anemia lack enough healthy red blood cells to carry a fully supply of oxygen to their tissues. The condition is often accompanied by weakness and exhaustion.
The space anemia study, financed by the Canadian Space Agency, is part of a larger project examining bone marrow health and blood production in space.
Since the human body has evolved to function under Earth’s gravity, the weightlessness of space flight creates challenges. When not subject to Earth’s gravity, weight-bearing bones lose up to 1.5 per cent of their mineral density each month. Astronauts also lose muscle mass faster than on Earth.
What’s more, in the microgravity of space, more blood goes to the head and chest. Scientists used to believe astronauts compensated for this by destroying red blood cells to reach a new equilibrium.
But Trudel’s research team found the destruction of red blood cells continued unabated in space. “What we found was a surprise,” Trudel said.
The phenomenon slowed as soon as the astronauts returned to Earth, but researchers found they were still destroying red blood cells at an accelerated rate one year later.
The study had an unusual design. The 14 astronauts enrolled in the study collected breath and blood samples throughout their time on the space station.
Those samples, stored in metal canisters, were sent back to Earth in a Space X cargo spacecraft and eventually delivered to researchers in Ottawa, where they were analyzed in a modified gas chromatograph capable of detecting carbon monoxide at the parts-per-billion level.
When a red blood cell dies, it releases one molecule of carbon monoxide. By measuring how many carbon monoxide molecules were in breath samples taken from the astronauts, researchers could discover how many of their red blood cells were being destroyed.
Trudel says he suspects space anemia is caused by the same mechanism that leads to anemia in hospital patients who spend weeks in intensive care beds.
A study conducted last year among 20 men who were on bedrest for 60 days found that they, too, destroyed significantly more red blood cells (23 per cent) than in the two weeks before they became inactive.
Trudel hopes to uncover the mechanism causing space anemia by studying why ICU patients and others immobilized for long periods of time develop anemia.