Effects of constitution, atraumatic vertebral fracture and aging on bone mineral density and soft tissue composition in women.

Constitution, atraumatic vertebral fracture and aging affect bone mineral density (BMD) and soft tissue composition. The high body weight of obese women involves a high mechanical load being exerted on weight bearing bones compared with thin women, which probably contributes to their higher BMD and the lower incidence of fractures in obese women compared with thin women. Atraumatic vertebral fracture (AVF) is a typical osteoporotic fracture and its favorite site of AVF is the vertebral bodies of the thoracolumbar region. The BMD of weight bearing bones is lower in patients with AVF than in patients without AVF, whereas there is no significant difference in soft tissue composition between the two. The regional and total BMD decrease with advancing age. The magnitude of the decrease in lumbar and thoracic BMD is high compared with other regional BMD, and total fat mass and total lean mass decline with age to their respective minimal level. The high rate of decrease in lumbar and thoracic BMD appears to be due to the high content of trabecular bone compared with other regional bones.