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Objective: To investigate the age at menarche, pubarche and telarche in a representative sample of residents of an urban zone of Leon, Guanajuato, Central Mexico and to evaluate the secular change of the age at menarche between 1985 and 2000. Methods: Using status quo and retrospective methods, menarcheal, pubarcheal and telarcheal status of girls 8 - 17 years of age (n = 1093) were determined. Multiple regression analysis and logistic regression were used to determine factors that were related to or predictive of age at menarche. Results: Median ages for menarche, pubarche and telarche in our studied sample were: 11.9 ± 0.04; 11.13 ± 1.25 and 10.84 ± 1.34 years, respectively. A direct correlation was found between the age of menarche of adolescents and that of their mother (p p p = 0.001), but an indirect correlation was found with the girls’ hip circumference (p = 0.004). We demonstrated a clear secular tendency towards an earlier onset of menarche by comparing our results (11.9 ± 0.04) with data from 1985 (12.8 ± 1.3) for adolescents from the same city. Conclusion: We demonstrated a clear reduction in age at menarche of approximately 0.75 year/decade, higher than Tanner’s finding in 1962, but similar than that of Malina et al. in 2004.

The Secular Tendency of the Age at Menarche in a Representative Sample of Mexican Girls from an Urban Zone in Central Mexico