Clinical usefulness of risk factors for osteoporosis.

Osteoporosis is a systemic skeletal disease characterised by loss of bone mass and microarchitectural integrity that lead to increased bone fragility and risk of fracture.' Its natural history is one of slow, progressive bone loss that often remains asymptomatic and undiagnosed for many years. Only when a substantial amount of bone has been lost do the characteristic low trauma fractures occur. Because osteoporotic fractures are associated with considerable morbidity, mortality, and cost,2 there is a need for methods of identifying individuals at risk earlier in the disease process, in whom preventative measures might be effective. Epidemiological studies have identified a wide range of population risk factors for low bone mass and osteoporotic fracture. These risk factors may relate to low peak bone mass, subsequent bone loss, or determinants of fracture independent of bone mineral density (BMD). Risk factors for low peak bone mass include low body mass index, low dietary calcium intake,3 physical inactivity, and smoking.4 Those associated with increased bone loss include many of those for low peak bone mass (but to varying degrees) with, in addition, corticosteroid drug treatment,5 previous low trauma fracture,6 7years elapsed since the menopause,8 and tooth loss.9 Risk factors for osteoporotic fracture independent of BMD may relate to poor bone quality or biomechanical determinants, for example a history of previous fracture'0 " or increased hip axis length,'2 or to an increased risk of falling, for example poor visual acuity, neuromuscular impairment, lower limb weakness, or long acting psychotropic drug treatment." The study of epidemiological risk factors for chronic diseases such as osteoporosis has several uses-first to provide insight into the aetiology, second to point the way towards population based preventative strategies (in this context, measures such as increasing physical activity and dietary calcium intake), and third to guide the clinical management of individual patients. In the case of osteo-porosis, this third application remains controversial,'4 15 and it is this that we shall discuss in the remainder of this article. The application of risk factors may prove to be of value through their modification in order to reduce subsequent fracture incidence, their incorporation into guidelines for clinical decision making, and their use to select for further investigation those with a high probability of low BMD. A number of risk factors for osteoporosis are potentially modifiable, and can be used to target specific areas for lifestyle advice. 16 These include smoking, high alcohol consumption, physical inactivity, …