Astronauts on International Space Station lose alarming amounts of hipbone strength, University of California-Irvine
"Astronauts spending months in space lose significant bone strength, making them increasingly at risk for fractures later in life. UC Irvine and UC San Francisco led a study evaluating 13 astronauts who spent four to six months on the International Space Station and found that, on average, astronauts' hipbone strength decreased 14 percent. Three astronauts experienced losses of 20 percent to 30 percent, rates comparable to those seen in older women with osteoporosis. These results alarmed researchers because they revealed a greater rate of bone deterioration than previously measured using less powerful technologies. "If preventive measures are not taken, some of our astronauts may be at increased risk for age-related fractures decades after their missions," said study leader Joyce Keyak, UCI orthopedic surgery and biomedical engineering professor."
Trip to Mars Will Challenge Bones, Muscles: Former Astronaut calls for More NASA Research on Exercise in Space, American College of Sports Medicine (2007)
"The rate at which we lose bone in space is 10-15 times greater than that of a post-menopausal woman," said Pawelczyk. "There's no evidence that bone loss ever slows (in space.) Further, it's not clear that space travelers will regain that bone on returning to gravity. Recent data suggests that not all people are recovering."
Testimony of Dr. James Pawelczyk at Senate Commerce, Science, and Transportation Committee Hearings: "International Space Station" (2003)
"We need the capability to house these organisms on the ISS and that's expected within five years. But equally important, we need time for crew members to prepare and conduct these experiments, and that time can be found only when the ISS moves beyond the core complete configuration. The potential return is immense; the application of this research to our aging public could become one of the most important justifications for an International Space Station."