Epidemiology and predictors of fractures associated with osteoporosis.

Approximately 40 in 100 women will experience one or more fractures after the age of 50 years. At 50 years for women the lifetime risk is 17.5% for hip fracture, 16% for vertebral fracture, and 16% for Colles' fracture; for men, the respective lifetime risks are 6%, 5%, and 2.5%. The incidence of hip fractures has increased in recent years in most but not all European countries, partly as a result of the aging of the population. However, the age-adjusted incidence has also increased in several countries. The age-adjusted incidence of hip fractures varies greatly between European countries; in women incidence varies from about 50 per 10,000 women in Malta and Poland to 500 per 10,000 in Sweden. In addition, the sex ratio (female:male) varies from 1.6 in Poland to 4.2 in Iceland. A proportion of this large variation may be the result of underreporting of cases, although most European countries now have an adequate hospital registration. The prevalence of vertebral deformities also shows geographic variation. In the multinational European Vertebral Osteoporosis Study, a population-based study, the prevalence of vertebral deformities was similar among men and women at ages 65-69 years (12-13%); at younger ages the prevalence was higher in men than women, whereas the reverse was true at older ages. Incidence data on vertebral fractures are scarce because a large proportion of vertebral fractures are not clinically diagnosed. Prospective epidemiologic studies indicate that bone mineral density (BMD) is the single best predictor of fractures in perimenopausal women. Historic risk factors do not predict bone mass (or fractures) with sufficient precision to be useful in assessment of fracture risk or BMD. However, the presence of one vertebral fracture doubles the risk of future vertebral fracture as assessed by a BMD measurement. At advanced ages, other risk factors may be more important, such as the risk of falling, and combinations of risk factors for falls and low BMD may predict hip fractures. Risk factor assessment is currently of less value for the prediction of other fractures, such as vertebral or Colles' fracture. Determining the causes of the large geographic differences in hip fracture incidence and the large differences in sex ratios for hip fractures in European countries could lead to identification of hitherto unknown risk factors and provide clues for prevention of fractures. Many risk factors cannot be prevented or modified; however, these risk factors (for example, family history, past fracture, and visual loss) can identify risk groups amenable to drug treatment or to preventive measures such as protective hip pads or environmental changes. Assessment of risk factors and definition of risk profiles are important steps toward the prevention of fractures in the elderly.