Over a 15 year period, women with low bone mineral density and a previous vertebral fracture had an increased risk of a new vertebral fracture compared to women with normal bone mineral density and no previous fracture, according to a study in the December 19 issue of JAMA: The Journal of the American Medical Association.
Vertebral fractures are the most common osteoporotic fracture, with prevalence estimates of 35 percent to 50 percent among women older than 50 years. About 700,000 vertebral fractures occur each year in the United States, according to background information in the article. Women with low bone mineral density (BMD) and previous vertebral fractures have a greater risk of new vertebral fractures over the short-term, but their risk of vertebral fracture over the long-term is uncertain.
Jane A. Cauley, Dr.P.H., of the University of Pittsburgh, and colleagues examined the absolute risk of new vertebral fractures by spine and hip BMD and previous vertebral fracture status over 15 years of follow-up in a group of 9,704 white women, who were recruited at four U.S. clinical centers and enrolled in the Study of Osteoporotic Fractures. Of these, 2,680 attended a clinic visit an average of 14.9 years after entering the study. The average age of the women was 68.8 years at entry and 83.8 years at follow-up.
The researchers found that of these 2,680 women, 487 (18.2 percent) experienced a new vertebral fracture, including 163 (41.4 percent) of the 394 with a previous vertebral fracture at baseline and 324 (14.2 percent) of the 2,286 without a previous vertebral fracture at baseline. Women who experienced a new fracture also weighed less, were more likely to have a positive fracture history and a previous vertebral fracture at study entry, and less likely to report estrogen use at baseline.