Do NASA Astronauts Age Faster in Space?

Space travel is an extraordinary feat for humankind, but it comes with a unique set of challenges for the human body, that can accelerate certain age-related health issues.

The transition from the weightlessness of space back to Earth’s gravity is anything but simple for astronauts.

NASA astronauts like Suni Williams and Butch Wilmore, who recently returned to Earth after spending nearly nine months aboard the International Space Station (ISS), face a range of health effects as they readjust to life on Earth.

One of the big questions raised by their extended stays in space is whether astronauts age faster due to the physical changes that occur during spaceflight.

Does Time in Space Affect Aging?

While astronauts don’t literally age faster in space, the prolonged exposure to microgravity and other space-related factors can accelerate certain age-related health issues.

It’s not the "passage of time" in space that makes astronauts age faster, but rather the physical stresses their bodies endure during space missions.

In space, the lack of gravity affects various biological processes. The bones lose density, muscles weaken, and the cardiovascular system undergoes changes similar to those seen in aging individuals on Earth. These effects are significant, but they are reversible to some extent once astronauts return to Earth and undergo rehabilitation.

However, the question remains whether these changes can mimic aging in ways that could shorten astronauts' lifespans or impact their long-term health. As an example, one of the most immediate effects of prolonged space travel is the weakening of bones and muscles.

In microgravity, the body does not have to support its weight, which leads to a gradual loss of bone density and muscle mass. Bones become about 1% less dense for each month spent in space, particularly in the legs, hips, and spine — areas that bear the brunt of Earth's gravity.

This phenomenon is similar to the bone loss seen in elderly individuals suffering from osteoporosis.

Without the constant pull of gravity, muscles also weaken due to reduced use, resulting in muscle atrophy. This is similar to the muscle weakening that comes with aging, making astronauts more vulnerable to falls and fractures when they return to Earth.

The heart and circulatory system also undergo changes in space, where the heart becomes more spherical in shape, affecting its ability to pump blood efficiently. Additionally, arterial stiffening and thickening, which are common in the elderly, have also been observed.

The health challenges faced by astronauts after a prolonged space mission are significant. After returning Earth, they must undergo a period of rehabilitation to recover their strength, adjust their cardiovascular systems, and address vision and neurological issues.

Though it can take months for astronauts to fully readjust to life on Earth, the information gained from studying these effects is invaluable, not only for future space missions but also for understanding human health in extreme conditions.