Is there a further acceleration in the age at onset of menarche? A cross-sectional study in 1840 school children focusing on age and bodyweight at the onset of menarche.

OBJECTIVE More than 30 years ago Frisch and Revelle proposed a body weight threshold for the onset of menarche. Based on this hypothesis, a further acceleration of age at menarche can be expected in times of childhood obesity. DESIGN A cross-sectional study of 1840 healthy school girls (Berlin school children's cohort, BSCOC) within the age groups 10-15 years was conducted in 2006-2007. METHODS Median age of menarche was calculated by Kaplan-Meier survival analysis. Bi- and multivariate analyses were performed to analyze the associations between menarche age and weight status. A locally weighted regression was used to analyze the relationship respectively between height, weight, and body mass index (BMI)-SDS and age stratified by menarche status. RESULTS Nine hundred and thirty six (50.9%) girls had already experienced menarche at a median age of 12.8 years. Two hundred and thirty six of these girls reached their menarche recently. Obese/overweight girls reached menarche significantly earlier (12.5 years), than normal weight (12.9 years), and underweight girls (13.7 years). The mean total body weight was similar in all girls at menarche irrespective of age (mean 51.1 kg, s.d. 8.1) and height. BMI-SDS remained the only significant factor for onset of menarche within a multiple regression model for early menarche (OR 2.1, 95% confidence interval 1.3-3.3, P=0.002). CONCLUSIONS Age at onset of menarche did not accelerate even in a childhood population with more than 10% obesity prevalence. Nevertheless, a negative correlation of BMI-SDS with age at onset of menarche exists.