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Recent decline in age at menarche: the Fels Longitudinal Study
Ellen W Demerath1, Bradford Towne, W Cameron Chumlea
1Lifespan Health Research Center, Department of Community Health, Wright State University School of Medicine, Dayton, Ohio 45435, USA. ellen.demerath@wright.edu
Summary
Recent studies suggest earlier menarche (first menstrual period) in US girls, possibly linked to rising childhood BMI. However, this study found no evidence of this link, indicating these trends are largely independent.
Area of Science:
- Pediatric Endocrinology
- Human Growth and Development
- Public Health
Background:
- Recent reports indicate a decline in the average age at menarche among US girls over the past two decades.
- This trend has been anecdotally linked to increasing childhood body mass index (BMI).
Purpose of the Study:
- To investigate the relationship between birth cohort, age at menarche, and body mass index (BMI) in girls.
- To determine if observed declines in age at menarche are causally linked to concurrent changes in childhood BMI.
Main Methods:
- Analysis of data from the Fels Longitudinal Study, including 371 girls across six 10-year birth cohorts (1930s-1980s).
- Examination of mean age at menarche and mean BMI measured cross-sectionally at ages 3-35 years for each cohort.
Main Results:
- Girls born in the 1980s experienced menarche approximately 3-6 months earlier than previous cohorts (P < 0.001).
- Mean BMI during childhood and adolescence remained constant across all birth cohorts.
- BMI increased in young and mid-adulthood for cohorts born in the 1960s and 1970s, without concurrent changes in age at menarche.
Conclusions:
- The study found no evidence supporting a causal link between declining age at menarche and increasing childhood BMI.
- Population-level changes in BMI and the timing of menarche appear to be largely independent processes.
- Adult BMI trends in later cohorts did not correlate with earlier menarcheal timing.