A three-year follow-up study on bone density development in Japanese peripubertal children

近几十年来，日本儿童骨折的发生率逐渐增加。对儿童骨折危险因素的调查可能有助于在以后的生活中预防骨折。我们在一项纵向研究中通过估计体积骨矿物质密度（vBMD）来检查生长中的儿童骨折的可能原因。我们检查了570名健康儿童（283名男孩），他们分别是义务学校4年级（10或11岁）至9年级（分别为G4至G9），他们的脊柱（LS）和全髋关节（TH）的实际骨密度（aBMD）通过DXA测量。受试者被邀请在基线后3年进行随访调查。调查对象432人，其中男生203人，占75.8%。在假定脊柱为圆柱体的情况下，在LS时估计vBMD。随着年龄的增长，两种性别在LS和TH基线时的身高和aBMD呈线性增加。在女孩中观察到类似的vBMD增加，但在男孩中没有，男孩在G6（12或13岁）时显示最低的vBMD。男孩在G6至G7和女孩在G4至G5期间身高和aBMD的年变化率最大。然而，男孩在G8 - G9和女孩在G7 - G8期间vBMD的年变化率最大。那些体重更重、牛奶摄入量更多、体育锻炼更多的人，骨密度的变化率更大。vBMD最低的年龄是身高增长速度最大的年龄，也是男女骨折发生率最高的年龄。与身高增长相比，骨密度增加的延迟可能导致骨密度低，这可能导致生长中的儿童骨折的短暂增加，并且可以通过改善本研究中发现的生活方式因素来预防。

Incidence of fracture in Japanese children has increased progressively in these decades. Investigations into risk factors for children's fracture may lead to prevention of fractures later in life. We examined possible causes of fractures in growing children by estimating volumetric bone mineral density (vBMD) in a longitudinal study.We examined healthy 570 children (283 boys) from 4th (10 or 11 years) to 9th grade of a compulsory school (G4 to G9, respectively) for whom areal BMD (aBMD) at the spine (LS) and total hip (TH) were measured by DXA. The subjects were invited for a follow-up survey 3 years after the baseline. 432 subjects (203 boys) (75.8%) completed the surveys. vBMD was estimated at LS under an assumption of the spine being a cylinder.Height and aBMD at LS and TH at baseline increased linearly with advancing in age in both genders. Similar increase was observed in vBMD in girls but not in boys, who showed the lowest vBMD in G6 (12 or 13 years). The greatest annual rate of changes in height and aBMD were observed during G6 to G7 in boys and G4 to G5 in girls. However, the annual rate of change in vBMD was the greatest during G8 to G9 in boys and during G7 to G8 in girls. The rates of change in BMDs were greater in those who had heavier weight, greater intake of milk and greater physical activities.The lowest vBMD was observed at the age of peak velocity of height growth which is the age at the highest fracture incidence in both genders. Delay in gaining bone density compared with height growth may cause low bone density, which may result in the transient increase in fractures in growing children, and may be prevented to improve the lifestyle factors found in this study.