Determinants of Bone Loss

The loss of bone mass and of its microarchitectural integrity is a slow process which remains asymptomatic until the appearance of the typical low trauma fracture. In order to effectively prevent the osteoporotic fractures methods of identifying individuals at risk earlier in the disease are needed. There are several different categories of risk factors for osteoporotic fractures. They may be related to the determinants of bone mineral density (BMD), to propensity for falling, and to skeletal fragility independently of BMD. The risk factors for the latter are relatively uncommon and poorly understood mainly because bone “quality” cannot be properly assessed in vivo. In some cases the risk factors can be generally defined as independent of BMD. This is the case for previous fractures, which are associated with an approximate doubling of fracture risk after correction for BMD (Ross et al. 1991), for the length of the head of the femur or for the thickness of the fat tissue overlying the hip (Reid et al.1994b; Cummings1995). In other cases the risk for fractures are linked to a greater liability to falls (poor visual acuity, neuromuscular impairment, inadequate lighting, use of benzodiazepines, age per se, etc.; Cooper et al.1988; Meyer et al.1995; Cummings et al.1995)