For astronauts who’ve spent months aboard the International Space Station, the risks to their hearts may not be as worrisome as once feared.
A new study tracking 13 NASA astronauts for up to five years after long-duration space missions finds no signs of accelerated vascular aging or emerging heart disease. The research, published July 10 in the Journal of Applied Physiology, suggests that arteries remain structurally and functionally normal even after extended exposure to microgravity, helping ease concerns about long-term cardiovascular health in space travelers.
No Thickening, No Stiffening, No Red Flags
Researchers used ultrasound to measure the astronauts’ carotid and brachial arteries before flight, in orbit, shortly after landing, and at regular intervals up to five years later. They found:
- No increase in carotid artery wall thickness or stiffness—early markers of heart disease
- Stable brachial artery vasodilation, a sign of healthy blood vessels
- Transient inflammation and oxidative stress postflight, which resolved within a week
- Only mild rises in cholesterol and blood sugar over time, consistent with normal aging
“Most indices of arterial structure and function in ISS astronauts were not different than preflight,” the authors wrote. “There were no signs, symptoms, or diagnoses of cardiovascular disease during the first [five years] after returning to Earth.”
Predicting Risk: Aging, Not Spaceflight, the Key Factor
To estimate the astronauts’ future cardiovascular risk, researchers used two tools: the American College of Cardiology/American Heart Association calculator, and a NASA-specific model called Astro-CHARM. Both showed a modest increase in 10-year risk, but this was largely attributed to aging rather than the effects of spaceflight.
For example, using the ACC/AHA tool, the average predicted risk rose from 2.6% before flight to 4.6% five years later. But when researchers plugged in only the age difference—keeping all other health markers constant—the risk still increased by 1.3% on average.
What About Deep Space Missions?
This study focused on astronauts who lived and worked in low Earth orbit, where Earth’s magnetic field provides some protection from cosmic radiation. The authors caution that future missions beyond Earth’s orbit—such as those planned for the Moon and Mars—may present greater cardiovascular risks due to higher radiation exposure and longer durations in microgravity.
Still, this research offers a reassuring sign: in the years after long-term spaceflight, astronauts’ arteries age much like those of healthy, active adults on Earth. “Astronauts appear resilient to the stressors of spaceflight,” the researchers concluded, calling for continued long-term health surveillance as missions grow more ambitious.
Real-World Implications for Space and Earth
These findings may also have ripple effects beyond the astronaut corps. Spaceflight is an extreme testbed for human physiology, and insights from space can help us better understand aging, cardiovascular disease, and resilience here on Earth. With more commercial astronauts and private space tourists entering orbit, having a better grasp of long-term heart health is more vital than ever.
Journal: Journal of Applied Physiology
DOI: 10.1152/japplphysiol.00264.2024
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