Regional variation in vertebral bone marrow adiposity: a population-based atlas of age- and sex-specific patterns.

Abstract

Background: Bone marrow adipose tissue (BMAT) is a metabolically active fat depot implicated in skeletal aging and systemic metabolism. While chemical shift-encoding MRI enables noninvasive quantification of bone marrow fat fraction (BMFF), current knowledge of vertebral BMAT is largely limited to small cohorts or restricted anatomical regions.

Purpose: To characterize the spatial distribution of vertebral bone marrow fat fraction across the spine and determine region-specific associations with age and sex in a population-based cohort.

Materials and methods: In this retrospective study, MRI data from 82,920 UK Biobank participants recruited between 2006 and 2010 were analyzed. The baseline case subset (n = 81,318) had a mean age of 54.8 ± 7.6 years, and 42,113/81,318 (51.8%) were female. Automated vertebral body segmentation enabled voxel-wise BMFF quantification using Dixon MRI. Vertebra- and region-level BMFF metrics were derived. Associations with age and sex were assessed using region-specific linear regression.

Results: Vertebral BMAT demonstrated a non-linear cranio-caudal pattern. Mean BMFF was ~ 39% in the cervical, ~ 55% in the thoracic, ~ 45% in the lumbar spine, and ~ 70% in the sacrum. BMAT increased with age in all regions (all p < 0.001; increase per decade: cervical 3.33%, thoracic 3.41%, lumbar 2.95%, sacral 3.83%). Females exhibited higher BMFF than males across all regions (all p < 0.001). The overall spatial pattern remained consistent across age groups and sexes.

Conclusion: Vertebral BMAT exhibits a structured, non-linear spatial distribution with region-specific age- and sex-dependent patterns. This population-based atlas provides normative reference data supporting region-specific BMAT assessment in skeletal and metabolic disease.