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

2005 Fiscal Year Final Research Report Summary

• Project/Area Number: 16590523
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Single-year Grants
• Section: 一般
• Research Field: Public health/Health science
• Research Institution: Kinki University
• Principal Investigator: IKI Masayuki Kinki University, School of Medicine, Professor, 医学部, 教授 (50184388)
• Co-Investigator(Kenkyū-buntansha): TAMAKI Junko Kinki University, School of Medicine, Lecturer, 医学部, 講師 (90326356) ; IKEDA Yukihiro Kinki University, School of Medicine, Research Associate, 医学部, 助手 (20368294) ; NAKA Hiroshi Kyoto University of Education, Faculty of Education, Associate Professor, 教育学部, 助教授 (00217639) ; SATO Yuho Tenshi College, Faculty of Nursing and Nutrition, Lecturer, 看護栄養学部, 講師 (10337115)
• Project Period (FY): 2004 – 2005
• Keywords: volumetric bone density / peak bone mass / lumbar spine bone density / hip bone density / adolescent / puberty / determinant / cohort study

Research Abstract

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.