Lean mass as a determinant of bone mineral density of proximal femur in postmenopausal women

ABSTRACT Objective: To verify which component of body composition (BC) has greater influence on postmenopausal women bone mineral density (BMD). Subjects and methods: Four hundred and thirty women undergoing treatment for osteoporosis and 513 untreated women, except for calcium and vitamin D. Multiple linear regression analysis was performed in order to correlated BMD at lumbar spine (LS), total femur (FT), femoral neck (FN) with body mass (BM), total lean mass (LM) and total fat mass (FM), all determined by DXA. Results: BM significantly correlated with all bone sites in untreated and treated women (r = 0.420 vs 0.277 at LS; r = 0.490 vs 0.418 at FN, r = 0.496 vs 0.414 at FT, respectively). In untreated women, the LM correlated better than FM with all sites, explaining 179% of LS; 32.3% of FN and 30.2% of FT; whereas FM explained 13.2% of LS; 277% of FN, 23.4% of FT In treated women, correlations with BC were less relevant, with the LM explaining 6.7% of BMD at LS; 15.2% of FN, 16% of FT, whereas the FM explained 8.1% of LS; 179% of FN and 176% of FT. Conclusion: LM in untreated women was better predictor of BMD than FM, especialy for distal femur, where it explained more than 30% of the BMD, suggesting that maintaining a healthy muscle mass may contribute to decrease osteoporosis risk. Treatment with anti-osteoporotic drugs seems to mask these relationships. Arch Endocrinol Metab. 2018;62(4):431-7摘要 研究目的：明确身体成分（body composition, BC）的各组分对绝经后女性骨密度（bone mineral density, BMD）的影响程度。 研究对象与方法：纳入430例接受骨质疏松治疗的女性，以及513例仅补充钙与维生素D的未治疗女性。采用双能X线吸收法（dual-energy X-ray absorptiometry, DXA）测定体质量（body mass, BM）、去脂体重总量（total lean mass, LM）及体脂总量（total fat mass, FM）；通过多元线性回归分析，探讨腰椎（lumbar spine, LS）、股骨总区域（total femur, FT）及股骨颈（femoral neck, FN）的骨密度与上述身体成分指标的相关性。 研究结果：体质量与未治疗组、治疗组女性的所有骨密度检测位点均呈显著相关（腰椎位点相关系数r分别为0.420与0.277；股骨颈位点r分别为0.490与0.418；股骨总区域位点r分别为0.496与0.418）。在未治疗组女性中，去脂体重总量与各骨密度位点的相关性优于体脂总量：去脂体重总量可分别解释腰椎骨密度变异的17.9%、股骨颈32.3%、股骨总区域30.2%；而体脂总量仅可解释腰椎13.2%、股骨颈27.7%、股骨总区域23.4%的骨密度变异。在治疗组女性中，身体成分与骨密度的相关性较弱：去脂体重总量仅可解释腰椎骨密度6.7%、股骨颈15.2%、股骨总区域16.0%的变异；体脂总量则可解释腰椎8.1%、股骨颈17.9%、股骨总区域17.6%的变异。 研究结论：在未接受抗骨质疏松治疗的绝经后女性中，去脂体重总量对骨密度的预测效果优于体脂总量，尤其在股骨远端位点，其对骨密度变异的解释度超过30%，提示维持健康的肌肉量可降低骨质疏松发病风险。而抗骨质疏松药物治疗似乎会掩盖上述身体成分与骨密度的相关性。 《内分泌与代谢档案》（Arch Endocrinol Metab），2018年；62(4):431-437