American journal of human biology : the official journal of the Human Biology Council;
OBJECTIVES: Worldwide data on age at menarche suggest a gradually earlier maturation, which is stabilizing in some societies. The interplay between socioeconomic, behavioral, and environmental factors generates uncertainty about the current status and future trend of age at menarche in most societies. Therefore, we aimed to describe trends in age at menarche during the 20th century in Portugal. METHODS: A sample of 11 274 women born between 1920 and 1992 in northern Portugal, recruited to participate in three population-based cohorts (EPIPorto, EPITeen, and Generation XXI) was evaluated. Age at menarche across birth year categories was compared using ANOVA and the rate of change over time using linear regression. RESULTS: Age at menarche decreased with birth year (-31.1 days per 5 years; β = -.017, P < .001), women born before 1930 having a significantly higher age at menarche than those who were born after 1990 (mean (SD) = 13.1 (1.83) vs 12.0 (1.25), P < .001). CONCLUSIONS: The decrease in age at menarche in northern Portugal suggests that a plateau is yet to be reached. Attention to time trends in age at menarche is relevant for health promotion since there is a possible relationship between pubertal timing and the later development of the metabolic syndrome.