In a study published Thursday in Scientific Reports, University of Calgary researchers have found that astronauts who spent more than three months in space aboard the International Space Station (ISS) only partially recovered from extensive bone loss. While the phenomenon naturally occurs in humans on Earth, the loss appears to be more prominent when the body is exposed to microgravity. In fact, the study’s authors found that six months in space resulted in decades worth of bone deterioration.

“Understanding what happens to astronauts and how they recover is incredibly rare,” Leigh Gabel, an assistant professor of kinesiology and lead author of the study, said in a press release. “It lets us look at the processes happening in the body in such a short time frame. We would have to follow someone for decades on Earth to see the same amount of bone loss.”

The issue stems from the microgravity environment of space. One of the biggest factors behind bone health is weight. Like muscles, bones need weight and stressors to maintain their strength. Without them, they become weakened over time. If your body is too underweight, it can lead to serious bone issues including osteoporosis, a disease that causes your bones to become so brittle that even a coughing fit could result in broken ribs.