title: A cross-sectional survey of factors influencing bone mass in junior high school students.
abstract: OBJECTIVE
  The purpose of this study is to investigate factors influencing the osteo-sono assessment index (OSI) in junior high school students (boys, girls who had reached menarche, and girls who had not).
  
  
  METHODS
  A total of 9,743 students (4,974 boys and 4,769 girls) in Ehime Prefecture participated in this study. We measured body mass index (BMI) and calcaneal bone mass using OSI. In parallel, participants answered a questionnaire relating to age, sex, menarche, exercise habits, milk intake, and history of bone fractures during the preceding year. To determine the factors influencing OSI, we calculated an individual standardized partial regression coefficient (β) using multiple linear regression (MLR) analysis.
  
  
  RESULTS
  For boys, MLR showed that BMI (β = 0.300), age (β = 0.260), current exercise habits (β = 0.106), and milk intake per day in primary school (β = 0.085) statistically significantly influenced OSI. For girls who had reached menarche, BMI (β = 0.302), current exercise habits (β = 0.237), age (β = 0.140), and bone fracture during the preceding year (β = 0.036) influenced OSI. For girls who had not reached menarche, current exercise habits (β = 0.242), BMI (β = 0.135), and age (β = 0.085) influenced OSI.
  
  
  CONCLUSIONS
  There were differences between the factors related to OSI among boys, girls who had reached menarche, and girls who had not. BMI, exercise habits, and age were the common factors related to OSI. Particularly for girls, exercise habits had a great influence on OSI.
authors.affiliation: Department of Applied Bioresource Science, The United Graduate School of Agricultural Sciences, Ehime University, 3-5-7 Tarumi, Matsuyama, Ehime 790-8566, Japan. tamura.yuka.my@ehime-u.ac.jp
authors.forename: Yuka
authors.initials: Y
authors.lastname: Tamura
authors.forename: Isao
authors.initials: I
authors.lastname: Saito
authors.forename: Yasuhiko
authors.initials: Y
authors.lastname: Asada
authors.forename: Taro
authors.initials: T
authors.lastname: Kishida
authors.forename: Masamitsu
authors.initials: M
authors.lastname: Yamaizumi
authors.forename: Tadahiro
authors.initials: T
authors.lastname: Kato
mesh_terms: D000293:Adolescent; D000367:Age Factors; D000818:Animals; D015992:Body Mass Index; D015519:Bone Density; D002111:Calcaneus / Q000502:physiology; D002648:Child; D003430:Cross-Sectional Studies; D015444:Exercise; D005260:Female; D050723:Fractures, Bone / Q000453:epidemiology / Q000209:etiology; D006801:Humans; D007564:Japan; D016014:Linear Models; D008297:Male; D008572:Menarche; D008892:Milk / Q000378:metabolism; D012737:Sex Factors; D013334:Students; D011795:Surveys and Questionnaires