Gender interactions between vertebral bone mineral density and fat content in the elderly: Assessment using fat-water MRI

Background: Adipose tissue is closely related to bone mass, bone quality, and bone fractures, but the connection between fat and bone is complex and gender-related. Fat-water magnetic resonance imaging (MRI) and MR spectroscopy (MRS) are very useful tools for identifying tissue fat.

Purpose: To assess gender interactions between bone mineral density (BMD), bone marrow fat, and body mass index (BMI) in the elderly using fat-water MRI and MRS.

Study type: Prospective/cohort.

Population: Sixty-six women and 38 men (mean age, 62.3 years; range, 50-75 years), Asian.

Field strength: A 1.5T MR equipped with a body and spine array coil. STEAM MRS and T₂ * Dixon were performed.

Assessment: Vertebral bone marrow fat ratio (MFR), BMI, and BMD were measured. Correlations between these variables and differences in bone density in MFR were assessed between participants, divided into three groups based on bone density.

Statistical tests: Multiple regression; Pearson tests; analysis of covariance; analysis of variance.

Results: Multiple regression analysis identified gender, vertebral bone MFR, and BMI as significant predictors of vertebral BMD (P < 0.001). Among the women, vertebral BMD was negatively correlated with vertebral MFR (P = 0.011), but among the men, it was positively correlated with BMI (P = 0.048), although this relationship was confounded by age and MFR. Moreover, vertebral bone marrow fat and BMI were indeed statistically uncorrelated in the elderly (P = 0.357 in women; P = 0.961 in men).

Data conclusion: We found gender interactions between fat and bone in the elderly. Higher bone marrow fat was correlated with lower trabecular BMD in older women but not in men. On the other hand, the positive correlation between BMI and BMD was more pronounced in men than in women.

Level of evidence: 2 Technical Efficacy Stage: 2 J. Magn. Reson. Imaging 2020;51:1382-1389.