Epidemiology of Age-related Bone Loss and Fractures

The central hypotheses of this project are (1) that age-related changes in bone mass/structure can be accounted for, in large part, by specific hormonal/biochemical parameters, loading forces, and the interactions between them; and (2) Bone stength estimates that can now be obtained clinically will enhance the ability to identify subjects at increased fracture risk.

To better understand age-related bone structural changes with aging we are analyzing both cross-sectional and longitudinal data from a continuing 6 year study involving 375 women and 325 men aged 20 to 97 selected randomly from the Rochester, MN area. The relationship of these changes with parameters such as sex steroids, bone biochemical markers and estrogen receptor and aromatase polymorphisms will be studied. In addition, the relationship of everyday loading forces to changes in voumetric bone mineral density (vBMD), bone geometry, and microstructure will be analysed.

To stay on the leading edge of research into osteoporosis we have developed new techniques to estimate bone strength. We have moved from the traditional dual-energy x-ray absorptionmetry (DXA) to novel assessments of volumetric bone mineral density (vBMD), structure, and indicies of bone strength by quantitative computed tomography (QCT) of the vertebrae and proximal femur and ultra-high resolution, peripheral QCT of the distal radius. Applying this new technology to a population-based, case-controlled study of postmenopausal Rochester women with vertebral and distal forearm fractures we will use Finite Element (FE) models to 1) quantify bone strength at the spine and distal radius and define key structural determinants of strength at each site; 2) to use measures of bone failure strength to improve current estimates of "factor-of-risk" (_, the ratio of applied load to that known to cause bone failure, i.e., fracture) for the vertebrae during various activities and to develop them for the distal radius with falls; 3) and to determine the utility of our new approaches in differentiating fracture cases from controls in comparison with conventional risk assessment using (DXA).