Nonvertebral fracture risk linked to low BMD in obese women
MedWire News: Obese postmenopausal women who sustain nonvertebral fractures have significantly lower bone mineral density (BMD) than women of similar age and weight who have not sustained a fracture, study findings indicate.
"Body mass index (BMI) is a major determinant of BMD, and obesity is widely believed to protect against fracture," note Melissa Premaor (Federal University of Santa Maria, Brazil) and colleagues.
"However, the higher BMD associated with obesity may reflect adaptation to increased mechanical demands on the skeleton and may not confer greater protection against fracture than lower BMD levels in leaner individuals, particularly in view of the greater trauma associated with falling in the obese population," they add.
Consistent with this hypothesis, the researchers recently observed a high prevalence of obesity in postmenopausal women with low trauma fracture.
To investigate further, Premaor and team compared BMD and other risk factors for nonvertebral fracture in 1377 obese (BMI >30 kg/m2) postmenopausal women who enrolled in the Study of Osteoporotic fractures between 1986 and 1988.
During a mean follow-up period of 11.3 years, 516 (37.5%) women sustained at least one nonvertebral fracture, most commonly at the hip (9.6%) or wrist (7.4%).
The researchers found that the prevalence of osteoporosis, measured shortly after study enrollment, was significantly higher in women with an incident fracture, than those without a fracture, at 11.7% versus 4.6%.
BMD T-scores in the spine, femoral neck, and total hip were significantly lower in obese women who experienced fractures than in obese women without fracture, with mean differences of -0.56, -0.46, and -0.51, respectively.
Logistic regression analysis revealed that each SD decrease in femoral neck BMD was independently associated with a significant 1.6-fold increase in the odds of nonvertebral fracture.
In addition, a history of fracture after 50 years of age was associated with a 1.7-fold increased likelihood of fracture.
"The finding of a significantly lower BMD on average in obese women with fracture compared with those without fracture, together with their significantly higher prevalence of previous fracture, provides important new evidence that fractures in the obese exhibit characteristics of fragility fractures," write Premaor and co-authors in the Journal of Clinical Endocrinology and Metabolism.
"Whether and how risk factors for fracture in obese and nonobese women differ requires further investigation," they conclude.
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By Laura Dean