NASA - National Aeronautics and Space Administration

Fact sheet number: FS-2001-02-39-MSFC
Release date: 03/01

Sub-regional Assessment of Bone Loss
in the Axial Skeleton in Long-Term Space Flight

Mission: Expedition Two, ISS Mission 5A.1, STS-102 Space Shuttle Flight

Experiment Location on ISS: n/a

Principal Investigator: Dr. Thomas F. Lang, University of California, San Francisco

Project Manager: David K. Baumann, NASA Johnson Space Center, Houston

As demonstrated by Skylab and Russian space station Mir missions, bone loss, which can increase the risk of fracture by weakening the skeleton, is an established medical risk in long-duration space flight. There is little information about the extent that lost bone is recovered after space flight. This experiment is designed to measure bone loss and recovery experienced by crew members on the International Space Station.

Experiment Operations

This study requires no in-flight operations. Bone loss in the spine and hip will be determined by comparing preflight and postflight measurements of crew members' spine and hip bones using Quantitative Computed Tomography -- a three-dimensional technique that examines the inner and outer portions of a bone separately. It can determine if the loss was localized in a small sub-region of the bone, or over a larger area.

Bone recovery will be assessed by comparing tomography data taken prior to crew members' flight, immediately after their return and one year later. The results will be compared with ultrasound measurements and Dual X-Ray Absorptiometry taken at the same times. Dual X-Ray Absorptiometry is a specially calibrated X-ray device that provides a two-dimensional measurement of the mass of an entire bone - the inner core, or trabecular bone, and the surrounding outer sheath, or cortical bone. The measurements taken will include Dual X-Ray Absorptiometry of the spine, hip and heel, and ultrasound of the heel.

The experiment begins with the Increment 2 crew members, but crew members on Increments 3 through 6 also will be measured, to augment the data. To determine how the bone loss in space compares to the range of bone density in a normal adult population, crew member bone measurements in the spine and hip will be compared to measurements of 120 healthy control subjects of different genders and races between the ages of 35 and 45.

Benefits

This study will provide the first detailed information on the distribution of spaceflight-related bone loss between the trabecular and cortical compartments of the axial skeleton, as well as the extent to which lost bone is recovered in the year following return. The study will provide information that could potentially be used in determining the frequency of crew member assignments to long-duration missions, and for studying their health in older age. It also may be of use in the design of exercise or pharmacological countermeasures to prevent bone loss. Finally, comparison of bone mineral density in the hip and spine between the gender and race subgroups in the control population will help to improve understanding of the prevalence of osteoporosis between different race and gender sub-groups.

Additional Information/Photos

For more information and photos on this and Expedition Two science experiments, visit:

http://www.scipoc.msfc.nasa.gov/

http://hrf.jsc.nasa.gov/

http://www.spaceflight.nasa.gov/