Low BMD, Vertebral Fractures Predict New Vertebral Fractures Within 15 Years

Laurie Barclay
December 18, 2007 — Low bone mineral density (BMD) and prevalent vertebral fractures in women are independently related to new vertebral fractures within 15 years, according to the results of a longitudinal cohort study reported in the December 19 issue of the Journal of the American Medical Association.
"Vertebral fractures are the most common osteoporotic fracture," write Jane A. Cauley, DrPH, from the University of Pittsburgh in Pennsylvania, and colleagues. "Women with low bone mineral density (BMD) and prevalent vertebral fractures have a greater risk of incident vertebral fractures over the short-term, but their absolute risk of vertebral fracture over the long-term is uncertain."
Of 9704 white women recruited at 4 US clinical centers and enrolled in the Study of Osteoporotic Fractures, 2680 attended a clinic visit at an average of 14.9 years after baseline evaluation. Mean age was 68.8 years at initial evaluation and 83.8 years at follow-up. The main endpoint was incident vertebral fractures identified from lateral spinal radiographs, defined as a decrease of at least 20% and 4 mm in vertebral height at any vertebral level.
Vertebral morphometry was used to identify prevalent vertebral fractures on baseline radiographs, and dual-energy x-ray absorptiometry was used to measure BMD at the total hip and lumbar spine.
Incident vertebral fracture at follow-up occurred in 487 women (18.2%) including 163 (41.4%) of the 394 with a prevalent vertebral fracture at baseline and 324 (14.2%) of the 2286 without a prevalent vertebral fracture at baseline (odds ratio [OR], 4.21; 95% confidence interval [CI], 3.33 - 5.34).
Low BMD predicted the long-term risk for incident vertebral fracture (OR per 1 SD decrease in total hip BMD, 1.78; 95% CI, 1.58 - 2.00). Absolute risk for vertebral fracture ranged from a high of 56% for women with a total hip BMD T score of −2.5 or less and a prevalent vertebral fracture, to a low of 9% in women with a normal BMD result and no prevalent vertebral fracture.
Women with prevalent vertebral fractures at baseline had a 4-fold increased risk for a new incident vertebral fracture during follow-up, and the magnitude of this association was dramatically higher than that observed for either age or BMD.
Limitations of the study include lack of generalizability to women of other ethnicities or to men, better baseline health in those who returned for follow-up, and total hip and lumbar spine BMD measured 2 years after the baseline radiographs.
"Low BMD and prevalent vertebral fractures are independently related to new vertebral fractures over 15 years of follow-up," the study authors write. "Women with a prevalent vertebral fracture have a substantially increased absolute risk of an incident fracture, especially if they have osteoporosis diagnosed by BMD."
The National Institutes of Health supported the Study of Osteoporotic Fractures. Some of the study authors have disclosed various financial relationships with Merck & Company, Eli Lilly & Company, Pfizer Pharmaceuticals, Novartis Pharmaceuticals, the National Institutes of Health, Amgen, GlaxoSmithKline, Merck & Co Inc, Novartis Pharma AG, Proctor & Gamble Pharmaceutical Co, Roche Laboratories, Wyeth Pharmaceutical, and Aventis.
JAMA. 2007;298:2761-2767.