Astronauts Lose 1.5% Bone Density a Month in Space as 70% Show Eye Symptoms
Updated
Updated · starlust.org · Jul 25
Astronauts Lose 1.5% Bone Density a Month in Space as 70% Show Eye Symptoms
2 articles · Updated · starlust.org · Jul 25
Summary
NASA data show astronauts on long ISS missions can lose 1% to 1.5% of bone mineral density each month, especially in the hips, pelvis and lower spine, because microgravity removes normal weight-bearing stress.
That same fluid shift toward the head cuts blood plasma volume by as much as 20%, while a 2022 Nature Medicine study found 54% more red blood cell destruction during six-month missions — a pattern dubbed space anemia.
Around 70% of astronauts on long-duration ISS flights show signs of spaceflight-associated neuro-ocular syndrome, in which pressure changes flatten the back of the eye, swell the optic disc and can leave blurred vision after return.
Daily exercise, calcium- and vitamin D-rich diets, bisphosphonates and experimental pressure suits help limit damage, but bone recovery can take years and no definitive fix exists for the eye changes.
The findings add to evidence that microgravity reshapes multiple body systems — previous research also found astronauts' spines can lengthen by up to 5 centimeters and raise post-flight disc risks.