A two-year longitudinal study on the determinant of bone mass gain at lumbar spine and hip during adolescence: the prevention of osteoporosis from adolescence

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For 412 first year students from 3 junior high schools and 316 first year high school students in Kyoto, we measured BMD by DXA at the lumbar spine (L2-L4) [LS] and total hip [TH], height, weight, and grip strength at baseline. We examined the same variables in 346 of the junior high school. students (127 boys and 219 girls, follow-up rate=84.0%) and 160 of the high school students (77 boys and 83 girls, follow-up rate=50.6%) again after 2 years respectively.1.There was a significant increase in BMD at the LS (junior high school students: boys=10.4%/yr, girls=6.0%/yr; high school students: boys=4.2%/yr, girls=1.4%/yr) and TH (junior high school students: boys=8.6%/yr, girls=5.3%/yr; high school students boys=4.1%/yr girls=2.7%/yr) in both genders; and the gender differences in the rate of change in BMD at both grades and sites were observed. Since third-year junior high school students tend to increase BMD more than third-year high school students, the junior high school years are very important for bone mass gain. 2.BMD at LS and TH increased with maturity in both genders for junior high school students but not high school students. However, the annual change rates in BMD decreased with progression of puberty. 3.BMD at the spine and hip increased with weight in both sexes for both age groups. 4.Boys and girls with more active lifestyles in junior high and high school showed greater BMD and change rates at LS and TH. Physical activity for both age groups was inferred to positively influence bone development in adolescents. 5.Sufficient calcium intake in the junior high and high school years was considered to influence acquisition of bone density positively; although there was no significant relationship between BMD and calcium intake.