A new risk calculator developed by researchers from the Women's Health Initiative (WHI) assesses a woman's risk of breaking a hip in the next five years. And it does so without considering bone density.
Bone density, as measured by dual energy x-ray absorptiometry (DEXA), is still the single most reliable indicator of a woman's risk of osteoporosis and hip fracture. But there's more to hip fracture risk than bone density. The WHI risk calculator — in the form of an online questionnaire — identifies 11 factors that, taken together, may predict hip fractures more accurately than bone density alone.
The importance of these risk factors emerged in the 1990s from a number of investigations — particularly the French EPIDOS (Epidémiologie de l'ostéoporose) study and, in the United States, the Study of Osteoporotic Fractures (SOF). EPIDOS included about 7,600 women ages 75 and over, and SOF involved nearly 8,000 women over age 65. In each study, women underwent DEXA testing and physical examinations and were interviewed about their lifestyles. Both studies found that fewer than half of the women who broke a hip had DEXA scans suggesting osteoporosis.
In response, researchers from the United States and Europe created a fracture index based on six risk factors, in addition to low bone density, that were identified in SOF — age, postmenopausal fractures, a mother's hip fracture, low weight, smoking, and relying on one's arms to get out of a chair. The index was tested on women in the EPIDOS study and found to predict hip fracture even when bone density wasn't included.
Inspired by these results, WHI researchers developed a more comprehensive index based on data from the nearly 94,000 women in their observational study. They fine-tuned some of the known risk factors and added new ones, including diabetes, inactivity, and corticosteroid use. A calculator based on this expanded list was tested on the 68,000 women in the WHI clinical trial and has been published in the Journal of the American Medical Association (Nov. 28, 2007). It's available online at http://hipcalculator.fhcrc.org.
The WHI researchers emphasize that the calculator hasn't been tested in the general population. Nor is it intended to help women make decisions about taking bone-density boosters like bisphosphonates (Fosamax, Boniva, Actonel, Zometa), raloxifene (Evista), or parathyroid hormone (Forteo). The calculator will probably be most useful to women with adequate bone density who want an additional way to gauge their hip fracture risk. It's also a good way to see the impact of lifestyle changes, such as taking up exercise or giving up cigarettes.