[Epidemiology and risk factors for osteoporosis]

It has been estimated that 40 % of white women aged 50 years will suffer at least one of the major osteoporotic fractures (hip, vertebrae, wrist) before the end of their life. Bone mineral density (BMD) measurement is the basis of osteoporosis diagnosis and is generally considered as a key element to identify high risk subjects who should benefit most from a bone active treatment preventive of fractures. However, for a given BMD level, the risk of fracture varies with age and with the presence of other risk factors (personal or familial history of fracture, low weight, corticotherapy, fall-related risk factors etc.). In the future, it is probable that densitometry results will be expressed in terms of risk of fracture within the next 10 years. Different intervention thresholds could then be defined depending on the age of the subject, the level and nature of the risk factors, as well as the type of preventive or therapeutic actions considered. In the elderly, fall-related factors such as neuromuscular and visual disorders have a weight similar to the one of BMD in the determinism of hip fracture. Recently, several randomized controlled trials have shown that multifactorial preventive programs tailored to individual risk factors or exercise programs emphasizing balance training can reduce the risk of falls in the elderly by 25 to 30%. The efficacy of such measures on fracture prevention must be demonstrated.