Site-specific Associations Of Muscle Thickness With Bone Mineral Density In Middle-aged And Older Men And Women

Abstract

It is well known that low bone mineral density (BMD) is a robust risk factor for fracture. Many studies have suggested that total skeletal muscle mass is positively associated with areal BMD (aBMD). However, it is unknown whether there are site-specific associations of muscle mass with aBMD. PURPOSE: To examine the relationships between lumbar spine and femoral neck aBMD and muscle thickness distribution in middle-aged and older men and women. METHODS: Sixty-seven healthy Caucasian adults (36 women and 31 men) aged 50 to 78 years volunteered for the study. Total (tLM) and appendicular (aLM) lean soft tissue mass, aBMD of the lumbar spine (LS-aBMD) and femoral neck (FN-aBMD) was estimated using dual-energy x-ray absorptiometry. Muscle thickness (MT) was measured by B-mode ultrasound at nine sites of the body (forearm, upper arm, trunk, thigh, and lower leg). Relationships of each predictor with aBMD were tested partialling out the effect of age. RESULTS: Both LS-aBMD and FN-aBMD were correlated to tLM (r=0.394, p<0.05 and r=0.463, p<0.01 respectively) and aLM (r=0.413, p<0.05 and r=0.479, p<0.01, respectively) in women. In men, tLM and aLM were only correlated with LS-aBMD (r=0.441 and 0.398, respectively, both p<0.05), but not FN-aBMD (r=0.304 and r=0.298, respectively). Summation of 9 MT was significantly correlated with both LS-aBMD and FN-aBMD in women (r=0.425, p<0.01 and r=0.610, p<0.001, respectively) and men (r=0.556 and r=0.494, both p<0.001, respectively). No significant correlations were observed between MT at the trunk and anterior lower leg and LS-aBMD or FN-aBMD in both sexes. In men, significant and relatively strong correlations were observed between anterior and posterior upper arm and anterior thigh MT and LS-aBMD (r=0.636, r=0.544 and r=0.566, respectively) or FN-aBMD (r=0.506, r=0.665 and r=0.444, respectively). In women, significant correlations were observed between anterior and posterior thigh and anterior upper arm MT and both LS-aBMD (r=0.369, r=0.398 and 0.391, respectively) and FN-aBMD (r=0.443, r=0.504 and r=0.502, respectively). CONCLUSIONS: aBMD was significantly associated with MT of the upper and lower extremities but not the trunk, which may be related to the participants’ daily physical activity profile.