What we know--and don't know--about bone loss in the elderly.

The incidence of fracture in women increases with age; yet studies of age-associated bone loss have shown conflicting results. Cross-sectional studies show that variation in bone content does not increase significantly with age, supporting the theory that there is a universal bone loss with age, and that women with low initial bone mineral are the most susceptible to osteoporosis. On the other hand, prospective studies show that people do lose bone at different rates. Both types of studies indicate that the rate of bone loss is significantly lower in elderly women than in those in the early postmenopausal period. The hallmark of osteoporosis is vertebral fracture, which is most often asymptomatic and increases in incidence in elderly women. However, there is considerable overlap in the amount of bone mineral in those with fracture and those without fracture. The overlap at fracture sites may indicate that factors other than low bone mass--such as osteomalacia--may play an important role in the development of fracture.