Plate Nº 58 · recorded October 1, 2026
Health & Medicine ResearchReported finding
Long Spaceflights Tied to Higher Hip Fracture Rates in Astronauts
A NASA-led study in Mayo Clinic Proceedings links spaceflights longer than 90 days to elevated hip fracture rates in astronauts, raising questions about long-term skeletal health.
By James Calloway4 min read900 words
In brief
- Hip fracture rates were higher among astronauts after spaceflights lasting more than 90 days.
- Hip fractures occurred at a younger age than expected compared with non-astronauts.
- NASA has begun ordering quantitative CT scans before and after spaceflight to better assess fracture risk.
Astronauts who spend more than 90 days in space break their hips at higher rates than those on shorter missions and higher rates than people who never leave Earth, according to a new study published in Mayo Clinic Proceedings. The fractures also occurred at younger ages than expected in a non-astronaut population, which the researchers describe as clinical evidence that spaceflight-induced bone loss carries real, long-term consequences.
The study, led by Jean D. Sibonga, Ph.D., of NASA's Johnson Space Center, carries weight for the agency's near-term plans. NASA is preparing multiple missions lasting more than six months, including commercial activity in low Earth orbit, the Artemis IV mission — the first human mission to the lunar south pole, planned for 2028 — and the development of sustainable surface capabilities on the Moon as a stepping stone toward Mars. As more people spend more time beyond Earth, the skeletal toll of prolonged spaceflight becomes a pressing medical question, even for astronauts selected for their exceptional physical fitness.
Why Space Weakens Bones
Bones and muscles deteriorate in the microgravity environment of space. The body, adapted on Earth to constantly work against gravity, essentially enters a state of disuse in orbit. The result is bone loss resembling what bedridden patients or people with severe immobility experience on the ground.
The problem has a hidden quality that makes it dangerous. "People do not feel the effects of bone loss," Sibonga noted. After returning from space, astronauts often feel stable or fully recovered and may resume physically demanding activities — even while their skeletons still carry changes from prolonged disuse. A clearer picture of post-flight bone health could help astronauts, their doctors, and even patients on Earth with disuse-related bone loss assess long-term risks, choose appropriate care, and avoid injuries.
Small Numbers, Statistical Muscle
Studying astronaut health is statistically tricky. Matthew T. Drake, M.D., Ph.D., of the Endocrinology and Metabolic Bone Disease Service at the Hospital for Special Surgery in New York, co-authored an editorial accompanying the study, titled "Bone Loss in Astronauts." He points to a persistent weakness in this field of research: "While data to date on bone loss associated with spaceflight are consistent, a major limitation is accuracy, as astronaut cohort sample sizes are small and spaceflights are rare."
To work around the small sample sizes, the investigators surveyed a cohort of U.S.-based astronauts about all fractures reported during their annual clinical exams. They then analyzed the data using Bayesian probabilistic modeling — a statistical approach that estimates the probability of an outcome rather than simply counting cases, which allows researchers to draw more reliable conclusions from limited data.
The results were specific rather than sweeping. The researchers did not find a higher incidence rate for fractures overall. But the rate of hip fractures was elevated after spaceflights lasting more than 90 days, compared with both shorter missions and the pre-mission baseline. It was also higher than among astronauts with no spaceflight exposure at all.
The hip, in other words, appears to be a specific point of vulnerability — and the fractures struck earlier in life than demographically expected.
"Taken together, the finding of hip fracture occurrence at an age earlier than expected after long-duration spaceflight is clinical evidence that spaceflight-induced bone loss can lead to real long-term fracture consequences, which should be addressed accordingly," says Moshe Gertzulin, M.D., also of the Hospital for Special Surgery's Endocrinology and Metabolic Bone Disease Service and a co-author of the editorial.
Better Scans, Safer Recoveries
Sibonga emphasized that NASA's current bone surveillance program needs to expand beyond dual-energy X-ray absorptiometry (DXA) — the standard scan that measures bone mineral density, the same tool used to screen for osteoporosis on Earth. DXA gives a two-dimensional measure of how much mineral is packed in the bone, but it cannot fully capture structural changes.
NASA has recently begun ordering quantitative computed tomography scans before and after spaceflight. These scans provide three-dimensional, more detailed information about different regions of the bone and can reveal whether an astronaut has fully recovered. That distinction matters. Without it, astronauts returning to intense physical activity risk loading bones that have not yet regained their preflight condition.
The investigators also advocate preventive measures aimed at preserving astronauts' baseline, preflight skeletal health rather than repairing damage afterward. A fuller characterization of how spaceflight changes bone mass, density, structure, and microarchitecture — the fine internal framework of bone tissue — would help determine which interventions work best: drugs, exercise, or dietary adjustments.
Caveats and Next Steps
The findings come with the limitations typical of astronaut health research. The cohort is small, spaceflights remain rare, and the observational design cannot prove that long-duration spaceflight directly caused the fractures — only that the two are associated. The authors themselves flag the accuracy limits of small-sample studies in this field.
Still, with Artemis IV on the calendar for 2028 and longer missions on the horizon, the study arrives at a moment when its practical implications are immediate. Determining how bone recovers after months in microgravity — and how to protect it before launch — may shape how NASA prepares its crews for the Moon, Mars, and beyond.
Publication details: "Increased Rates of Hip Fractures Associated With Longer Spaceflight Durations," Mayo Clinic Proceedings (2026). DOI: 10.1016/j.mayocp.2026.06.025.
via Phys.org Space & Astronomy (Source)