MONDAY, Nov. 8 (HealthDay News) -- Because weightlessness during space flight can cause people to experience rapid bone loss, long missions may take a toll on crew members' bones, according to researchers.

In a new study, lead investigator Dr. Shreyasee Amin, an associate professor at the Mayo Clinic, and colleagues analyzed bone mineral density (BMD) measurements in 28 U.S. space crew members (24 males, four females) whose space missions ranged from 95 to 215 days. BMD is an indicator of bone strength.

All 28 crew members had their BMD measured before their space flight and within 33 days after their return to Earth. In addition, 24 members of the group had their BMD checked again between six and 18 months after returning from space.

BMD measurements were taken for the total body, the hip, the lumbar area of the spine, and two sites at the wrist. The crew members' BMD results were compared with healthy adults who had never left Earth.

The astronauts' BMD immediately after space flight was much lower than normal and consistent with what is known about bone loss during space flight, said the researchers. But, the investigators also found that about 12 months after crew members returned from space, BMD at several locations was still lower than normal.

The findings indicate that an extended period in a low-gravity environment could have a long-term harmful effect on bone health.

The study is scheduled for presentation Nov. 9 at the annual scientific meeting of the American College of Rheumatology (ACR), held in Atlanta.

"Ideally, we need to identify better strategies to prevent the bone loss that occurs during space flight so that we can keep the bones of those serving on long-duration space missions healthy and strong for the long-term," Amin said in an ACR news release.

More information

NASA has more about bones and space travel.