DEXA Limitations
Specifically, DEXA does not indicate who will fracture. In the Study of Osteoporotic Fractures (a longitudinal study of over 8,000 women over age 65), the majority of hip fractures occurred in women who did not have osteoporosis based on BMD. (14) In a meta-analysis of how well BMD predicts fracture the authors found that a 1 SD reduction in BMD resulted in a relative risk of 1.6 (95% CI 1.5-1.7) for any fracture. Although this is statistically significant, the authors concluded that BMD is a weak predictor of who will fracture. (15)
The correlation between BMD and fracture risk also varies substantially between races and ethnic groups. For example, for every level of BMD, black women have a 30-40% lower fracture risk than white women. (16)