Bone Marrow Adiposity Assessed by HRpQCT Is Related to Fracture Risk and Bone Mineral Density in Older Swedish Women.

Context: Recent research links bone marrow adiposity (BMAT) to osteoporosis and fracture risk. Typically, BMAT is assessed via magnetic resonance imaging (MRI), a costly and less accessible method. A new method uses high-resolution peripheral quantitative computed tomography (HR-pQCT) to quantify BMAT.

Objective: To investigate if BMAT, derived from HR-pQCT images, is associated with fracture incidence and osteoporosis prevalence in older women.

Methods: 2984 women aged 75-80 years from the SUPERB cohort were included between March 2013 and May 2016. Bone characteristics, including bone densitometry (DXA) and HR-pQCT of the ultra-distal tibia, were assessed. Bone marrow fat fraction (BMFF) was measured using HR-pQCT. Incident fractures were tracked until March 2023. Linear regression was used to analyze associations between BMFF, anthropometrics, and bone mineral density (BMD). Cox and Poisson regression examined BMFF's association to incident fractures.

Results: BMFF was inversely associated to body mass index (r= -0.21, p < 0.001) and hip BMD (r = -0.50, p < 0.001). Over a median follow-up of 7.3 years, 797 major osteoporotic fractures (MOF), 1069 any fractures, and 235 hip fractures occurred. Higher BMFF (per SD) increased the risk of MOF (HR = 1.24, 95% CI 1.15-1.34), any fracture (HR = 1.20, 95% CI 1.12-1.28), hip fracture (HR = 1.22, 95% CI 1.06-1.40), and vertebral fracture (HR = 1.24, 95% CI 1.12-1.38) in multivariable Cox models adjusted for age, body mass index and clinical risk factors. Mediation analysis indicated that a significant proportion of these associations were mediated by femoral neck bone mineral density (FN-BMD).

Conclusion: Higher BMFF is associated with lower BMD and higher fracture risk in older women.