Space Anaemia

Since the first space mission, it was noted that space travel makes astronauts anaemic- a condition termed “space anaemia”. But why exactly this happens has long remained a mystery.

In space, astronauts experience a shift of body fluids towards the upper half of the body due to a lack of gravity. This leads to higher pressure on the brain and eyes, causing cardiovascular issues. Space anaemia was thought to be the body’s way of acclimatising to this cephalad fluid shift. Also, the red blood cell loss was considered temporary, with the levels restored to normal after the astronauts’ first ten days in space.

The first set of findings published from MARROW in the journal Nature Medicine throws some light onto this issue. MARROW, led by principal investigator Dr Guy Trudel, is a five-year study funded by the Canadian Space Agency to understand more about the effects of microgravity on bone marrow and the number and function of blood cells produced within it. They analysed the blood and breath samples of 14 astronauts during their six month stays at the International Space Station between 2015 and 2020.

The team developed methods to measure red blood cell destruction (haemolysis). Each time one heme molecule is destroyed, one carbon monoxide molecule is released. So, CO levels can be used as a direct measure of haemolysis.

The analysis of the samples showed that space flight leads to higher levels of haemoglobin degradation, carbon monoxide concentration in alveolar air etc. Further studies revealed that 50% more RBCs are destroyed in space, which persists throughout the space mission. A year after the astronauts’ space mission, these effects were still observed in their blood and breath samples.

Even though the team could not measure the levels of RBC production in the astronauts, they expect that the astronauts experienced the generation of extra red blood cells. Else, the astronauts would have suffered from the aftereffects of severe anaemia. However, in the case of a lengthy space mission, researchers are not sure how long the body can withstand this haemolytic condition.

Thanks to weightlessness, fewer red blood cells are not a problem in space. But when the astronauts return to Earth or land on other planets or moons, the reduction in RBC levels can impact the individuals’ energy, endurance and strength. This situation can even threaten the mission objectives in the case of humans landing on extra-terrestrial worlds without the aid of medical supervision. Anaemia is experienced only when the individual starts to experience gravity again.

The anaemia associated with space flight is similar to that observed in patients who remained inactive for months in intensive care suffering from illnesses such as COVID-19. Like astronauts patients experience very little force on their skeleton, like astronauts, leading to bone marrow fat accumulation. If the exact mechanisms that underlie space anaemia are understood, it is possible to find a cure for it. It would be a help for astronauts and anaemic patients alike.

This study suggests that astronauts who are a part of lengthy space missions have to adapt their diets to make more iron and eat more calories for energy, i.e., to support better blood health. The study also implies that astronauts and space tourists must be screened for blood or health conditions affected by anaemia.