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Good news for astronauts: Arteries remain normal years after long-duration spaceflight

The structure and function of astronauts' arteries appear to remain stable and free of disease for as long as five years after they've returned from the International Space Station (ISS), according to a new study in the Journal of Applied Â鶹ÒùÔºiology.

Studies have shown changes in astronauts' bodies after spaceflight, including in the and . In the short-term, adaptations in the human cardiovascular system in microgravity include less blood circulating throughout the body, a decreased ability to physically exert themselves, and dizziness or lightheadedness when standing after returning to Earth. But the evidence is less clear about the long-term effects of long-duration spaceflight on a person's body.

The new study, which involved 13 NASA astronaut volunteers, aimed to shed more light on these long-term effects. In their late 30s to late 50s when they began their ISS missions, the astronauts spent between four months to nearly a year in space.

Researchers studied ultrasound images of the volunteers' carotid and brachial arteries (located in the neck and arm, respectively) before launch, during spaceflight, one week after return to Earth and up to three times in the five years after landing. In addition, the research team also reviewed the astronauts' medical data in those five years after landing and compared them to data collected before flight.

Key findings of this study included:

• Higher levels of most markers of inflammation and oxidative stress observed in blood and urine samples during spaceflight resolved within one week after landing.
• No observed increased carotid artery thickening or stiffness. These increases are hallmarks of future cardiovascular disease.
• Brachial artery vasodilation, a subclinical marker of cardiovascular disease that measures the health of blood vessels, remained stable over time.
• Total cholesterol and glucose levels rose moderately over seven years of observation but hemoglobin A1C did not, suggesting that heart disease and diabetes risks did not rise as a result of spaceflight.

Using the medical data in a risk estimation tool developed for the general population that predicts developing heart disease within the next 10 years, the researchers found that risk increased from 2.6% to 4.6% from before spaceflight to five years after landing. However, calculated risk increased only by an additional 0.5% when using an estimation tool developed from a population with similar health characteristics to astronauts.

The astronauts self-reported that they maintained an active lifestyle after their mission, including those who retired from the astronaut corps. Notably, the researchers explained that natural aging of the astronauts accounted for most of the increase in predicted risk.

"[W]e report that most indices of arterial structure and function in ISS astronauts were not different than preflight and that there were no signs, symptoms, or diagnoses of cardiovascular disease during the first [five years] after returning to Earth from long-duration spaceflight," the researchers wrote. "Thus, [the cardiovascular system of] astronauts appear resilient to the stressors of spaceflight."