Secular changes in head dimensions of Japanese females over eight decades

The aim of this work is to document secular changes in the head dimensions of Japanese adult females. The data set of the current study was compared with two others, one covering 1910–1917 and the other 1975–1979. The subjects of the present study were all of Japanese birth and ancestry, and were aged 18–25 years. Four head dimensions were measured: head length, head breadth, head height, and head circumference. The subjects’ height and body weight were also recorded. The mean head length, head breadth, and cephalic index were larger in the present study than in the 1910–1917 series. Head length, head height, and head size (circumference) were larger in the the current series than in the 1975–1979 series. However, head breadth and cephalic index in this series were somewhat larger than in the current series. Results of ANOVA showed significant differences (P < 0.01) for all birth-year cohorts from 1978 to 1983 in terms of head length, head breadth, and head circumference. Head height, cephalic index, height, and weight, however, did not display significant differences. Regression analysis revealed that all measurements, including the cephalic index, had decreased. These results indicate that although brachycephalization has been occurring for the last 85 years, the cephalic index has decreased over the last two decades in adult Japanese females.