Medina-Gomez Carolina, Heppe Denise H M, Yin Jia-Lian, Trajanoska Katerina, Uitterlinden André G, Beck Thomas J, Jaddoe Vincent W V, Rivadeneira Fernando
Department of Internal Medicine, Erasmus University Medical Center, Rotterdam, The Netherlands.
The Generation R Study Group, Erasmus University Medical Center, Rotterdam, The Netherlands.
J Bone Miner Res. 2016 May;31(5):1099-106. doi: 10.1002/jbmr.2755. Epub 2016 Jan 8.
Bone strength, a key determinant of fracture risk, has been shown to display clear sexual dimorphism after puberty. We sought to determine whether sex differences in bone mass and hip bone geometry as an index of strength exist in school-age prepubertal children and the degree to which the differences are independent of body size and lean mass. We studied 3514 children whose whole-body and hip scans were measured using the same densitometer (GE-Lunar iDXA) at a mean age of 6.2 years. Hip dual-energy X-ray absorptiometry (DXA) scans underwent hip structural analyses (HSA) with derivation of bone strength indices. Sex differences in these parameters were assessed by regression models adjusted for age, height, ethnicity, weight, and lean mass fraction (LMF). Whole-body bone mineral density (BMD) and bone mineral content (BMC) levels were 1.3% and 4.3% higher in girls after adjustment by LMF. Independent of LMF, boys had 1.5% shorter femurs, 1.9% and 2.2% narrower shaft and femoral neck with 1.6% to 3.4% thicker cortices than girls. Consequent with this geometry configuration, girls observed 6.6% higher stresses in the medial femoral neck than boys. When considering LMF, the sexual differences on the derived bone strength indices were attenuated, suggesting that differences in muscle loads may reflect an innate disadvantage in bone strength in girls, as consequence of their lower muscular acquisition. In summary, we show that bone sexual dimorphism is already present at 6 years of age, with boys having stronger bones than girls, the relation of which is influenced by body composition and likely attributable to differential adaptation to mechanical loading. Our results support the view that early life interventions (ie, increased physical activity) targeted during the pre- and peripubertal stages may be of high importance, particularly in girls, because before puberty onset, muscle mass is strongly associated with bone density and geometry in children. © 2015 American Society for Bone and Mineral Research.
骨强度是骨折风险的关键决定因素，已表明在青春期后呈现明显的性别差异。我们试图确定在青春期前的学龄儿童中，骨量和作为强度指标的髋部骨骼几何结构是否存在性别差异，以及这些差异在多大程度上独立于体型和瘦体重。我们研究了3514名儿童，他们在平均年龄6.2岁时使用同一台骨密度仪（GE-Lunar iDXA）进行了全身和髋部扫描。髋部双能X线吸收法（DXA）扫描进行了髋部结构分析（HSA），并得出骨强度指标。通过对年龄、身高、种族、体重和瘦体重分数（LMF）进行调整的回归模型评估这些参数的性别差异。经LMF调整后，女孩的全身骨密度（BMD）和骨矿物质含量（BMC）水平分别高出1.3%和4.3%。独立于LMF，男孩的股骨比女孩短1.5%，骨干和股骨颈窄1.9%和2.2%，皮质厚1.6%至3.4%。由于这种几何结构，女孩在内侧股骨颈处的应力比男孩高6.6%。考虑LMF时，得出的骨强度指标的性别差异减弱，这表明肌肉负荷的差异可能反映了女孩在骨强度方面的先天劣势，这是由于她们较低的肌肉获取量所致。总之，我们表明骨性别差异在6岁时就已存在，男孩的骨骼比女孩更强壮，其关系受身体成分影响，可能归因于对机械负荷的不同适应。我们的结果支持这样一种观点，即在青春期前和青春期阶段进行的早期生活干预（即增加身体活动）可能非常重要，特别是对女孩而言，因为在青春期开始之前，肌肉质量与儿童的骨密度和几何结构密切相关。© 2015美国骨与矿物质研究学会。
