Secular trends for takeoff and maximum adolescent growth for eight decades of Japanese cohort data.

The presence of secular trends in the onset or takeoff of the adolescent growth spurt and subsequent adolescent growth of Japanese boys and girls were investigated using data published in "The Statistical Report of the School Health Survey" by the Ministry of Education, Science, Sports and Culture, Japan. An optimum kernel regression method was used to derive the biological parameters of the adolescent growth curve. An increasing trend in height at takeoff (i.e., height at the onset of the adolescent growth spurt) and height at peak height velocity (PHV) among Japanese children was evident during the 8 decades covered in this study. Age at PHV (i.e., the timing of the maximum adolescent growth) for each sex has decreased. Age at takeoff (i.e., the timing of the onset of the adolescent growth spurt) has decreased in boys during this century, but was almost constant in girls at about 7.8 years of age. Moreover, the interval between age at takeoff and age at PHV in girls has gradually decreased over this century. Since the birth year 1915, velocity at takeoff for girls was markedly greater than that for boys, whereas peak height velocity for girls was significantly less than that for boys (P < 0.05). Am. J. Hum. Biol. 12:702-712, 2000. Copyright 2000 Wiley-Liss, Inc.