#Anemia #Space #Microgravity #Hemolysis #RBC
#Astronauts
Space anemia is a well-known phenomenon among
astronauts, observed since the earliest manned missions. It is characterized by
a
decrease in red blood cell count and hemoglobin concentration, which can
affect oxygen transport capacity, physical performance, and post-flight
recovery. Until recently, this anemia was considered
transient and
adaptive—primarily due to
early changes in plasma volume and a
temporary
reduction in erythropoiesis linked to microgravity.
However,
new clinical data show that
anemia
persists well beyond the first few weeks of spaceflight—and sometimes for
several months after return. These findings suggest the presence of an
active
and prolonged pathological mechanism that could significantly impact
astronaut
health.
Against this backdrop,
this study aimed to
determine whether hemolysis—i.e., increased destruction of red blood cells—is a
central mechanism in persistent space anemia.
Does space destroy our red blood cells?
Fourteen astronauts who participated in missions lasting 167 ± 31 days between
2015 and 2020 were included in the study. Samples of alveolar air, ambient air,
and blood were collected before, during, and up to one year after the mission.
Exhaled endogenous carbon monoxide (CO), a key marker of hemoglobin
degradation, was measured to assess the extent of hemolysis.
The results showed a
54% increase in CO
elimination during spaceflight, indicating
persistent hemolysis throughout the
mission. This hemolysis was still observed on
day 157—well beyond the initial
fluid shift adaptations. It appeared to be
independent of both erythropoietin
(EPO) levels and plasma volume changes.
Additionally, blood markers associated with
hemoglobin breakdown were
consistently elevated in space, pointing to
increased
hemolysis. Four days after return, these markers dropped significantly,
reflecting a return to Earth’s gravity. However, even
a year later, some
indicators remained altered: exhaled CO was still
30% higher, reticulocytes had
increased by
16%, and hemoglobin concentration was
3.5% higher. These results
confirm that
microgravity has long-lasting effects on erythropoietic
regulation.
Flying—but at what cost?
Space anemia is a well-documented effect of human spaceflight, marked by a
reduction in red blood cells during and after orbital missions. Previously
considered a short-term adaptation to microgravity, it can in fact persist
beyond the initial weeks in space—and even months after returning to Earth. One
of the major challenges lies in understanding its long-lasting mechanisms.
This study set out to determine whether
hemolysis plays a
central role in space anemia. The findings reveal
a
significant and sustained increase in hemolysis throughout the entire mission,
independent of fluid shifts or EPO levels. Even one year post-flight, key
biomarkers remain partially altered, suggesting a
lasting impact of
microgravity on erythrocyte homeostasis.
These results pave the way for
new research
into hematological adaptations in space. They highlight the urgent need for
targeted monitoring and countermeasures to preserve red blood cell integrity
during long-duration missions—especially with
future crewed missions to Mars on
the horizon.
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