Obesity and fractures in postmenopausal women

Abstract

Low body mass index (BMI) is a recognized risk factor for fragility fracture, whereas obesity is widely believed to be protective. As part of a clinical audit of guidance from the National Institute of Health and Clinical Excellence (NICE), we have documented the prevalence of obesity and morbid obesity in postmenopausal women younger than 75 years of age presenting to our Fracture Liaison Service (FLS). Between January 2006 and December 2007, 1005 postmenopausal women aged less than 75 years with a low-trauma fracture were seen in the FLS. Of these women, 805 (80%) underwent assessment of bone mineral density (BMD) by dual energy X-ray absorptiometry (DXA), and values for BMI were available in 799. The prevalence of obesity (BMI 30 to 34.9 kg/m(2)) and morbid obesity (BMI > or = 35 kg/m(2)) in this cohort was 19.3% and 8.4%, respectively. Normal BMD was reported in 59.1% of obese and 73.1% of morbidly obese women, and only 11.7% and 4.5%, respectively, had osteoporosis (p < .0001). Multiple regression analysis revealed significant negative associations between hip T-score and age (p < .0001) and significant positive associations with BMI (p < .0001) and previous fracture (p = .001). Our results demonstrate a surprisingly high prevalence of obesity in postmenopausal women presenting to the FLS with low-trauma fracture. Most of these women had normal BMD, as measured by DXA. Our findings have important public heath implications in view of the rapidly rising increase in obesity in many populations and emphasize the need for further studies to establish the pathogenesis of fractures in obese individuals and to determine appropriate preventive strategies.