Risk Of Early Onset Osteoporosis Due To Spaceflight

Bone minerals decline in microgravity, and bone mineral density (BMD) losses of approximately -1 to -1.5% per month were calculated for astronauts serving on long-duration missions prior to 2009. It is unclear whether BMD losses will stabilize with time in space, or continue to diminish with time. In addition, it is unknown if fractional gravity, present on the moon and Mars, will mitigate the mineral loss. Clinicians diagnose osteoporosis in premenopausal females and males younger than 50 years on the basis of BMD T-scores < -2.5 (hip and lumbar spine) accompanied by clinical evidence of a fragility fracture. If mission-related changes to the skeleton cannot be corrected by rehabilitation after the mission, crewmembers could be at risk for premature osteoporosis-related fractures in later life. To mitigate this risk it is necessary to understand the dynamics underlying the BMD changes that occur in microgravity, to monitor for the persistence of changes after space flight, and to evaluate if and how current and future osteoporosis treatments might be used to mitigate the risk of long-term skeletal problems in astronauts.