A new NASA-funded study revealed how bone loss increases
the risk of injuries, highlighting the need for additional
measures to ensure the health of spacecraft crews.
The study provides new information about bone loss caused by
prolonged spaceflight. The study is in the online version of
the Journal of Bone and Mineral Research.
The research team was from the University of California San
Francisco (UCSF) and Baylor College of Medicine, Houston. The
team used three-dimensional X-ray computed tomography (CT) to
study the effect of prolonged weightlessness on the bone
mineral density and structure of the hip in a group of 14
American and Russian International Space Station crewmembers.
The crewmembers spent from four to six months onboard the
Station. The research suggests additional conditioning
exercises and other countermeasures may be necessary to prevent
bone mineral loss.
“This study underlines the importance of continuing to develop
countermeasures to preserve musculoskeletal conditioning in
long-duration space travelers,” said Guy Fogleman, director of
Bioastronautics Research in NASA’s Office of Biological and
Physical Research, Washington. “Results of this research, which
may aid people on Earth who suffer for similar conditions
including osteoporosis, are being shared with the medical
community,” he added.
This study is the first to use CT imaging to three-
dimensionally quantify spaceflight-related bone loss in the hip
and to estimate changes in hipbone strength. Previous studies
used a two-dimensional imaging technology called dual X-ray
absorptiometry.
The CT measurements in the hip were performed pre- and post-
flight to measure bone loss in the porous bone in the interior
of the hip and in the dense outer shell of the hipbone. On
average, the Station crew lost interior bone at a rate of 2.2
to 2.7 percent for each month in space and outer bone at a rate
of 1.6 to 1.7 percent per month.
“Our study demonstrates that bone loss occurs in the Space
Station crewmembers at a rate comparable to that observed
almost a decade before in the crew of the Russian Mir
spacecraft,” said Thomas Lang, UCSF associate professor of
radiology and principal investigator on the study. “The lack of
clear progress in the interval between Mir and Station missions
indicates a need for continued efforts to improve
musculoskeletal conditioning regimens during longer space
missions, such as those proposed for the moon and Mars,” Lang
said.
The investigators used information from the CT images to
estimate changes in the strength of the hipbone. They found on
average the hipbone strength declined by 2.5 percent for each
month of flight. Since the amount of bone loss increases with
mission length, crewmembers on multiyear explorations may face
increased risk of fracture upon return to Earth gravity. In
addition, those who do not recover the lost bone may be at
increased risk of fracture as they age.
The researchers also analyzed loss of density in vertebrae
(back bones). Vertebrae, along with the hip, are the skeletal
sites associated most with serious osteoporotic fractures in
the elderly. The study found on average, the Station crew lost
vertebral bone at a rate of 0.8 to 0.9 percent per month, which
was consistent with data from earlier long-duration missions.
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