Decline in pubertal timing and its relationship with excess weight. A study of the secular trend in age at menarche in girls from La Plata district (Buenos Aires, Argentina)

Objective: To provide information on the secular trend in age at menarche (AgM) in Argentinean girls in relation to excess weight (EW) and body adiposity. Methods: Two cohorts (C) (C1, 2005-2007 and C2, 2015-2019) of children aged 8-14 years from La Plata district were studied using identical methodological criteria. Each participating child was asked about menarche (M) status: M presence (MP) or absence (MA). The AgM was estimated using the status quo method and logistic regression analysis. Body weight, height, and tricipital and subscapular skinfolds were collected to estimate EW (overweight + obesity) according to WHO criteria, and body adiposity (sum of skinfolds, SSK = [tricipital + subscapular]). The prevalence of EW by C was estimated and compared using the Chi-square test. The MP probability in relation to age, C, and EW was analyzed by applying logistic regression. Parents completed a questionnaire to assess family socioeconomic conditions. Data were compared using the Chi-square test. Results: Differences in MP prevalence between C were significant (C1: 21.1% vs. C2: 28.7%). Median AgM was 12.81 years in C1 and 12.22 in C2. The prevalence of EW was higher in C2 (35.3%) than in C1 (24.6%). The probability of MP was higher in C2 than in C1 and children with EW. Both BMI and SSK showed inter-cohort increases. Socioeconomic conditions were substantially deteriorated between C. Conclusion: In an obesogenic context marked by the significant increase in body adiposity and EW, M prevalence exhibited a positive secular trend and AgM reduced by nearly seven months between the cohorts studied.