Body Weight Determines Directly Bone Mineral Density in an Irish Referral Population

Abstract

Background: Obesity moderates the effect of osteoporosis by a number of ways: bone strength is augmented by an increase in bone mineral density (BMD) and by more robust bone geometry; padding at site of trauma dissipates the energy reducing fracture liklihood; but, lower level of activities lead to trauma and obese persons have more falls and higher impact of fall. We sought to evaluate the influence of age, gender, height, weight, and dietary calcium intake on BMD at spine and hip. Methods: In consecutive sample of patients referred to our DXA service (n 5 5999), we evaluated the relationship between BMD at both spine and femur with the following variables: age, gender; height; weight, body mass index; and calcium intake, correlation analysis, univariate analysis of variance, and forward multiple regression analyses using SPSS for Windows version 16.0 (SPSS, Chicago, IL). Results: Anthropometric indices (height, weight, BMI) had stronger correlation than age, sex or calcium intake with both lumbar BMD and femur BMD. Univariate analysis of variance identified weight as being the major factor accounting for variance in BMD at spine and femur. Forward multiple regression yielded a model for predicting both lumbar BMD and femur BMD with weight being the strongest predictor. The models accounted for 20% of variance of spine BMD, and for 37% of variance of hip BMD (Table 1). Conclusion: Among a large sample of patients referred to our DXA service, body weight is the best determinant of BMD, with age have a substantially smaller effect, sex and height having a minimal effect, and calcium intake having no effect.