Scientists from the University of Calgary and elsewhere have followed 17 International Space Station astronauts before and after spaceflight over the last seven years to understand whether bone recovers after ‘long-duration’ spaceflight. Their results show that while bone partially recovers after the flight, sustained losses represent at least a decade of normal age-related bone loss, potentially advancing onset of osteoporosis.
Gabel et al. examined bone strength, density, and microarchitecture in seventeen astronauts using high-resolution peripheral quantitative computed tomography. Image credit: NASA.
“The detrimental effect of spaceflight on skeletal tissue can be profound,” senior author Dr. Steven Boyd from the University of Calgary and his colleagues wrote in their paper.
“Decreases in mechanical loading in microgravity cause substantial loss of bone mineral density and strength and the deterioration of trabecular microarchitecture.”
“Biochemical studies of bone turnover highlight altered bone metabolism during spaceflight, such that biomarkers of bone resorption increase during spaceflight, while biomarkers of bone formation lag, resulting in net bone loss.”
“Recovery of bone mineral density and strength upon return to Earth’s gravity is a lengthy process, and many astronauts’ bones never completely recover,” they added.
“Determining who is at greatest risk for incomplete recovery of bone tissue is important for understanding feasibility of missions beyond low-Earth orbit.”
“The primary aim of our study was to use high-resolution peripheral quantitative computed tomography to examine recovery of bone microarchitecture, density, and strength after long-duration spaceflight.”
The prospective study included 17 astronauts (14 males and 3 females; mean age – 47 years; height – 177.7 cm; body mass – 79.1 kg) from NASA, Canadian Space Agency (CSA), European Space Agency (ESA), and Japan Aerospace Exploration Agency (JAXA) who were selected for missions to the International Space Station (ISS).
The authors imaged the participants before spaceflight, at return to Earth, and after six and 12 months of recovery.
They conducted bone scans on the tibia (shinbone) and radius (forearm) to calculate the resistance of the bone to fracture (failure load), bone mineral in the bone tissue, and tissue thickness.
They also recorded exercises such as cycling, treadmill running and deadlifting completed by astronauts in-flight and post-flight.
One year after flight the median results for 16 of the astronauts showed incomplete recovery of the shinbone.
Median shinbone failure load, measuring bone strength, was reduced by 152.0 newtons (N) from 10,579 N at pre-flight to 10,427 N after one year.
Total bone mineral density reduced by 4.5 mg/cm3 compared to pre-flight levels of 326.8 mg/cm3.
Measures of the forearm across all astronauts did not differ at 12 months’ recovery compared to pre-flight.
The researchers observed that astronauts on missions longer than six months (a total of eight astronauts) had substantially less bone recovery.
In astronauts on missions over six months the median shinbone failure load reduced by 333.9 N after one year compared to pre-flight, while in astronauts on missions shorter than six months (nine astronauts) the failure load reduced by 79.9 N.
Similar differences were found for total bone mineral density in the shinbone.
Altogether, nine of the astronauts (seven from long missions) did not fully recover shinbone total bone mineral density after 12 months.
Across all astronauts, those who completed greater amounts of in-flight deadlift training, relative to their individual training pre-flight, were identified as part of those who recovered tibia bone mineral density.
“As well as currently used exercise routines, a jumping resistance-based exercise that provides high-impact dynamic loads on the legs may help prevent bone loss and promote the formation of bone on spaceflight missions,” the scientists said.
Their paper was published June 30, 2022 in the journal Scientific Reports.
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L. Gabel et al. 2022. Incomplete recovery of bone strength and trabecular microarchitecture at the distal tibia 1 year after return from long duration spaceflight. Sci Rep 12, 9446; doi: 10.1038/s41598-022-13461-1
Source link: https://www.sci.news/space/spaceflight-bone-strength-density-10963.html
