Influence of body composition and fat distribution on bone mineral density in elderly Italian women

Introduction: There is now a substantial body of evidence indicating that bone mass is related to fat mass. However the relationships between body composition, fat distribution, bone mass and bone turnover markers still remain controversial. This study aimed to investigate the relative contribution of body composition and fat distribution to bone mass in a large cohort of elderly women. Methods: We studied 939 postmenopausal women (65.5 ± 11.1 years) living in the area of Siena (Italy). In all patients BMD was assessed at lumbar spine (BMD-LS), at femoral neck (BMD-FN) and at total femur (BMD-TF). Whole body mineral content (BMC), fat mass (FM), lean mass (LM), android fat (AF), ginoid fat (GF) and bone mineral density (BMD-WB) were assessed by using a DXA device (Lunar GE). In all we measured 25-hydroxyvitamin D (25OHD), bone alkaline phosphatase (B-ALP), parathyroid hormone (PTH) and carboxy- terminal telopeptide of type I collagen (CTX). Results: After adjusting for body weight GF showed inverse association with BMD-FN (P <0.01), BMD-TF (P < 0.05), BMD-LS (P = 0.06) and BMD-WB (P < 0.05). No significant correlations were found between AF and BMD. Moreover LM was significantly correlated with BMD at all skeletal sites (P < 0.05) and in particular with BMD-FN (r = 0.21 P < 0.001). PTH was positively correlated with FM (P < 0.01) and AF (P < 0.05), but not with GF and LM. Conclusion: Our results suggest that adiposity, after controlling for body weight is inversely correlated with BMD, whereas LM showed positive effects on BMD. The negative influence of fat on bone may be influenced by PTH.