[Age at menarche among schoolgirls in Odense. Is age at menarche still decreasing in Denmark?]

The average age at the menarche has decreased from the 1850s to the 1950s. It is controversial whether there has been a continued decrease since the 1950s. The object of this investigation is to illustrate whether this trend has continued into the 1980s. This study is based on the ages at the menarche as recalled by 908 girls aged 14-16 years in 40 schools in Odense. The information was obtained during intervals of differing lengths and consequently, the parameters of the distribution of the age at the menarche were estimated in a randomly grouped normal distribution. The average age at the menarche was found to be the same throughout the municipality (13.27 years; 95% confidence limit 13.20-13.35). The variations were found to be significantly differentiated by the type of school district. The variations were low in the suburbs and in the surrounding rural districts, higher in the inner city areas and highest among girls attending private schools. Compared with the results from other recent Danish studies, these findings suggest a halt in the decline of the average age at the menarche, which may be temporary.