Age-related vBMD decline varies by gender, anatomic site
MedWire News: Age-related changes in volumetric bone mineral density (vBMD) and vertebral strength are greater in the lumbar spine than the thoracic region and greater in women than men, researchers have found.
The findings confirm the importance of evaluating the determinants of vertebral strength in the thoracic and lumbar spine and in men and women to understand the mechanisms that underly the structural failure of vertebral bodies with aging, say Elizabeth Samelson (Harvard Medical School, Boston, Massachusetts, USA) and co-authors.
They used volumetric phantomless quantitative CT (QCT) scans to evaluate vBMD, geometry, and strength in the thoracic (T8-T10) and lumbar (L3-L5) spine and determine how these parameters vary with age, gender, and spinal region.
The study, published in the Journal of Bone and Mineral Research, involved 690 participants (n=344 women) with a mean age of 61 years, from the Framingham Heart Study Offspring and Third Generation Multi-detector Computer Tomography Study. The average body mass index was 28 kg/m2 in women and 29 kg/m2 in men.
The findings revealed that the decline in vertebral integral vBMD (including cortical and trabecular compartments, excluding transverse and posterior processes) with increasing age was twice the magnitude in women than men for the lumbar spine and more than four times greater in women than men for the thoracic spine.
Integral vBMD declined more at the lumbar spine than at the thoracic spine for both women and men. Indeed, integral vBMD at the thoracic spine decreased 29% in women between the ages of 40 and 75 years of age, compared with 6% in men. But at the lumbar spine, integral vBMD decreased 36% from 40-75 years in women and 18% in men.
Trabecular vBMD declined to a similar extent with age in the lumbar and thoracic regions for men and women.
In women and men, vertebral cross-sectional area increased significantly less and the factor-of-risk increased significantly more with age at the lumbar than thoracic region. Indeed, in women, the factor-of-risk for forward flexion worsened with age 6.8-times more in the lumbar compared with the thoracic spine.
There was little or no significant age-related change in the forces applied to the thoracic vertebrae in either women or men, write the authors, but age-related changes were greater in the lumbar spine than the thoracic region and greater in women than men.
"These results help explain the greater frequency of vertebral fracture in women than men, and also, the high predictive value of lumbar spine bone density for predicting fracture," conclude the authors.
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By Piriya Mahendra