Early skeletal deteriorations following short-duration spaceflight

The adverse effects of spaceflight on skeletal health are well documented; however, the onset and underlying mechanism of these changes remain poorly understood. This study investigated alterations in bone microarchitecture, density, strength, and remodeling in eight crew members (four males, four females) aboard the SpaceX Crew Dragon spacecraft as part of the Fram2 and Polaris Dawn missions. The primary aim of this study was to investigate the impact of short-duration spaceflight (3-5 days) on bone strength and microarchitecture to determine the onset of bone deterioration. Secondary objectives included examining how these changes compared to typical age-related bone loss and potential sex-specific differences in the skeletal response to microgravity. High-resolution peripheral quantitative computed tomography (HR-pQCT) scans of the distal radius and tibia were performed pre- and post-spaceflight. Postflight, the tibia demonstrated significant reductions in total bone density (p < 0.05), and adverse alterations in trabecular bone microarchitecture, including decreased trabecular bone density (p < 0.05), trabecular thickness (p < 0.01) and separation (p < 0.05). In contrast, the radius exhibited no significant changes in bone density, microarchitecture or strength. These findings suggest there is early onset of bone loss and microstructural changes following 3-5 days in microgravity, highlighting the value of short-duration missions for studying skeletal deterioration that may be used for the future development and assessment of targeted skeletal countermeasures.