Density and Fat Fraction of the Psoas, Paraspinal, and Oblique Muscle Groups Are Associated With Lumbar Vertebral Bone Mineral Density in a Multi-Ethnic Community-Living Population: The Multi-Ethnic Study of Atherosclerosis

Low vertebral bone mass is a major risk factor for vertebral compression fractures. While sarcopenia has been shown to be associated with low bone mineral density (BMD), it is not known whether trunk musculature is directly associated with lumbar BMD, and whether exercise modifies this association. Using data from the Multi-Ethnic Study of Atherosclerosis (MESA), we sought to determine the association of muscle density and fat fraction of the psoas, paraspinal, and oblique muscle groups with L3 lumbar volumetric BMD, and whether these associations were modified by exercise. We obtained L3 vBMD measurements, and fat and muscle measurements (in Hounsfield units (HU)) from abdominal CT scans spanning L2-L4 intervertebral disc spaces. Muscle density was defined as the mean HU value for a muscle group area. Fat fraction was calculated as the mean HU value for the muscle group fat area/total muscle group area(sq cm). Exercise data were self-reported (MET-min/wk). We utilized multivariable linear regression to evaluate these associations, stratified by gender, and adjusting for demographics, BMI, smoking status, impaired fasting glucose, and corticosteroid and anti-resorptive medication use. Among 1923 MESA participants, mean age was 62±10, 49% were female, 40% White, 21% Black, 26% Hispanic/Latino and 13% Chinese. In fully adjusted analysis, for every 1 SD higher psoas fat fraction, there was a 3.19 SD lower L3 vBMD in men and 4.3 SD lower SD L3 vBMD in women (p