Fig. 3: Returning from 167-day missions on the ISS modulated the bone marrow adiposity at the lumbar vertebrae of 14 female and male astronauts as measured using 3 different quantitative MR techniques.

a Bone marrow fat fraction (BMFF) using proton density with and without fat saturation. b BMFF using DIXON. c BMFF using MR Spectroscopy (MRS). BMA accrual in female astronauts 1 year after long-duration spaceflight abolished the preflight sex difference, shown with all 3 MR techniques. d Change in BMFF measured from an average of all 3 MR quantitative techniques. e Change in BMFF in male astronauts. f Change in BMFF in female astronauts. BMFF was lower in male and in female astronauts 41 days after landing compared to preflight (both *P < 0.05). BMFF was higher 6-months and 1-year postflight in female astronauts compared to preflight and compared to male astronauts (all P < 0.05). The shaded grey area corresponds to the time onboard the International Space Station. Boxes show 2 quartiles around the median. Whiskers indicate minimum and maximum values excluding outliers. *P < 0.05 compared to preflight BMFF by two-sided Wilcoxon Signed Rank test (n = 14). #P < 0.05 between male and female astronauts by two-sided Mann–Whitney U test (n = 14) with no adjustment for multiple comparisons.