Lack of linkage between height and weight and age at menarche during the secular shift in growth of Japanese children.

During the past century, Japanese children have shown a most dramatic secular trend toward earlier menarche and accelerated tempo of growth. In order to assess the inter-relationship between these dual secular trends, we analysed the data on height and weight measurements of Japanese children, collected by the Japanese Ministry of Education in the years from 1900 through 1986, with reference to various retrospective studies on the age of menarche among Japanese. Between 1950 and 1983, both the mean height and weight at menarche varied significantly but percentage of the mean height achieved at menarcheal age, as compared with the mature height, remained relatively stable at approximately 95%. The results indicate that the secular trend toward earlier menarche reflects largely, if not solely, the secular change in tempo of physical growth in Japanese children.