Six months in space equals a decade of bone loss

Astronaut Scott Kelly
Astronaut Scott Kelly

During space missions lasting six months or longer, astronauts can suffer bone loss equivalent to a decade of aging on Earth, a new study has revealed.

Bones “are a living organ,” said Leigh Gabel, a scientist at the University of Calgary in Canada who was responsible for the study, published recently in Scientific Reports. “They are alive and active and in constant remodeling,” he added. However, without gravity, the bones lose strength.

For the development of this study, Gabel and her team followed 17 astronauts – 14 men and three women, with an average age of 47 years -, who spent between four to seven months in space.

Using high-resolution tomography scans, which allow the measurement of bone architecture on scales “thinner than the thickness of a human hair”, the researchers analyzed the structure of the tibia, in the leg, and the radius, in the arm, calculating its strength and density.

The images were collected in four moments: before the space flight; when they returned from space; six months after returning and then another six months (totaling one year).

The results showed that astronauts who spent six months or less in space were able to regain bone strength a year after returning. However, those who stayed longer experienced permanent bone loss in the tibias, equivalent to a decade of aging.

In contrast, in the radius there were no significant losses, probably because it is a bone that does not carry as much weight, said Gabel.

According to Steven Boyd, a researcher at the University of Calgary, quoted by Science News, an increase in the frequency and number of weightlifting exercises in space could help alleviate bone loss.

To the Guardian, Boyd, who is one of the authors of the study, compared the bones of the human body to the Eiffel Tower. Some of the metal rods that hold the structure together are lost and never recovered, he explained. To compensate, others thicken.

“With longer spaceflights, we can expect greater bone loss and probably a greater recovery problem,” said physiologist Laurence Vico of the University of Saint-Étienne in France, who was not part of the study.

Muscle loss is quite worrying when considering NASA’s plans to send astronauts into deep space. A simulation done in 2020 suggests that, in a three-year spaceflight to Mars, 33% of astronauts would be at risk of developing osteoporosis (progressive loss of bone mass).

As astronauts exercise more in space, researchers should continue to investigate whether muscle loss has a ceiling or whether it continues to occur as the time spent in space increases.

Source: With Agencies

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