Age, Weight and Body Mass Index Effect on Bone Mineral Density in Postmenopausal Women

Background: Osteoporosis is a multifactorial skeletal disease, whose mechanisms are not fully understood. It is more common in older people, especially in postmenopausal women. Objectives: Body mass index (BMI) has been suggested as an important measurement to assess bone mineral density (BMD). Therefore, the aim of this study was to assess the effects of age, weight and BMI on BMD in postmenopausal women. Patients and Methods: In a cross-sectional study based on BMD measurement using dual-energy X-Ray Absorptiometry ( DEXA) method, 80 postmenopausal women referred to Rheumatology Clinics in Zahedan were selected; 26 participants had osteoporosis, 28 had osteopenia, and 26 had normal bone density. Weight and height were obtained to calculate BMI. Results: The mean BMD of women older than 50 years compared to those younger than 50 years was significantly different (P < 0.05). The mean weight and BMI were found to be significantly lower in patients with low BMD as compared to the normal group ( P<0.0001). There was a negative significant association between age and low BMD only in femur neck region (r = - 0.37, P = 0.006). In addition, a direct association was observed between weight (r=0.41, P = 0.002) and BMI(r=0.31, P = 0.02) with BMD at lumbar spine. Conclusions: The findings indicated that older women with low BMI were at higher risk of low bone mass. Body weight, BMI and aging may be important predictors of BMD, but they are not the only factors affecting bone loss. Therefore, it is recommended to assess other risk factors with a larger number of patients.