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

近几十年来，日本儿童的骨折发病率呈递增趋势。对儿童骨折危险因素的调查可能会导致在以后的生活中预防骨折。在纵向研究中，我们通过估计体积骨密度(VBMD)来研究生长中儿童骨折的可能原因。我们检查了570名健康儿童(283名男孩)，从4(10岁或11岁)到9年级(分别为G4到G9)，用DXA测量了脊柱(LS)和全髋部(TH)的面骨密度(ABMD)。受试者在基线3年后被邀请进行随访调查。432名调查对象(203名男孩)(75.8%)完成了调查。腰椎的vBMD是在假设脊柱为圆柱体的假设下估算的。在男女两性中，腰椎和TH的身高和aBMD都随着年龄的增长而线性增加。女孩的vBMD也有类似的增加，但男孩没有，他们在G6(12或13岁)表现出最低的vBMD。身高和aBMD的年变化率最大的是男孩的G6到G7和女孩的G4到G5。然而，男孩vBMD的年变化率在G8至G9期间最大，女孩在G7至G8期间最大。体重越重，牛奶摄入量越多，体力活动越多，骨密度变化率越大，身高增长最快的年龄，也就是男女骨折发生率最高的年龄，骨密度最低。与身高增长相比，延迟获得骨密度可能会导致骨密度低，这可能会导致生长中儿童骨折的一过性增加，并可能被阻止，以改善本研究中发现的生活方式因素。

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.