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April 11, 2019
When astronauts return to Earth, their carotid arteries, which carry blood to the head and neck, appear to have aged 20 to 30 years. Artery walls become stiffer and thicker in space, the same as when people grow older on Earth.
Arterial and other aging-related changes seem to accelerate during time spent in space. For example, after six months in space, astronauts also show signs associated with developing insulin resistance.
Animation above: Spaceflight causes changes in the heart and arteries that resemble accelerated aging. Animation Credit: NASA.
A number of earlier investigations aboard the International Space Station first recognized this accelerated aging in the carotid artery, representing a potential significant long-term risk for astronauts. Results from two investigations, Vascular and Vessel Imaging, suggest that a daily session of aerobic or cardio exercise is not sufficient to counteract what amounts to an otherwise sedentary lifestyle in microgravity.
One of the latest investigations into this phenomenon is Vascular Aging, sponsored by the Canadian Space Agency (CSA). It uses ultrasounds of arteries, blood samples, oral glucose tolerance tests, and wearable sensors to look for early indicators of cardiovascular aging. The resulting data may point to mechanisms to reduce the risk of such aging.
“You can take extremely healthy, fit astronauts and put them in an environment that restricts their ability to do daily exercise, and they run the risk of developing insulin resistance that on Earth could lead to Type II diabetes,” said principal investigator Richard L. Hughson of Schlegel-University of Waterloo in Ontario, Canada. “We know that on Earth, Type II diabetes is strongly associated with sedentary behavior.”
Image above: Canadian Space Agency astronaut David Saint-Jacques wearing the Bio-Monitor, a Canadian technology designed to measure and record astronauts’ vital signs. The Vascular Aging investigation uses the shirt to collect data. Image Credits: Canadian Space Agency/NASA.
A special shirt provided by the CSA, the Bio-Monitor, records the physical activity of astronauts during the day along with their heart rate and respiration. Other devices take regular blood pressure readings and estimate arterial stiffness. These measurements enable researchers to assess relationships between an individual’s metabolism, or ability to regulate blood sugar in the body, and aging-like symptoms of the arteries and bones. Crew members also take blood samples so researchers can identify and detect biomarkers that may predict early signs of cardiovascular aging. The investigation takes the same measurements before, during and after spaceflight.
“We believe we’ll see higher levels of glucose for a period of time after each meal, similar to that seen in people with Type II diabetes on Earth,” Hughson said. “Those elevated levels can cause glucose to bind to protein molecules in the blood and to proteins in the blood vessel walls, which contributes to arterial stiffness.” That effect is largely irreversible, but others are likely reversible once astronauts return to Earth.
Image above: Canadian Space Agency astronaut David Saint-Jacques performs an ultrasound for the Vascular Echo experiment, one of the trio of experiments in the Vascular group that includes Vascular Aging. Image Credit: NASA.
“If we do see elevated glucose after meals, the best way to prevent that is by introducing more physical activity,” he said. “There are ways to accomplish that rather than spending another hour on the treadmill. You have to be active for different periods throughout the day.”
Changes in diet, such as decreasing salt and cholesterol, also can contribute to vascular health, improving some markers of arterial stiffness. A better understanding of the daily interaction of exercise and diet can help lead to developing preventative measures that delay or even reverse some of the effects of aging, both in space and on Earth.
Another CSA-sponsored study underway by members of the same research team, Vascular Echo, monitors arterial stiffness for up to six months post-flight to help determine whether space-related changes are reversible.
“The idea is to keep blood glucose regulation optimal in our daily lives, both with physical activity and diet interventions,” Hughson said. “Fortunately, we expect the blood glucose response to recover fairly quickly when they get back to Earth and resume normal activities.”
Take that, old and stiff arteries.
Related links:
Vascular Aging: https://www.nasa.gov/mission_pages/station/research/experiments/explorer/Investigation.html?#id=7644
Vascular Echo: https://www.nasa.gov/mission_pages/station/research/experiments/explorer/Investigation.html?#id=1664
Bio-Monitor: https://www.nasa.gov/mission_pages/station/research/experiments/explorer/Facility.html?#id=7392
Canadian Space Agency (CSA): http://www.asc-csa.gc.ca/eng/
Space Station Research and Technology: https://www.nasa.gov/mission_pages/station/research/index.html
International Space Station (ISS): https://www.nasa.gov/mission_pages/station/main/index.html
Animation (mentioned), Images (mentioned), Text, Credits: NASA/Michael Johnson/JSC/Melissa Gaskill.
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