Another FM smack-down: chemicals are not causing earlier puberty
Summary: Another day, another error uncovered. To see others go to the reference page FM Smackdowns (corrections to and attacks on FM posts).
(1) “Are children today really going through puberty earlier?“, Darshak Sanghavi, Slate, 19 August 2010 — Conclusion:
But in the end, the epidemic of earlier and earlier puberty is a myth that the media love and certain researchers continue to propagate. The tale’s promotion doesn’t always depend on data. Instead, worries about earlier physical maturation in girls sublimate and propel concerns about society’s sexualization of young girls, whether by provocative dance routines or revealing clothing. Those topics certainly get people talking. Unfortunately, any solutions are unlikely to come from the labs of our nation’s endocrinologists.
(2) “Age at menarche and racial comparisons in US girls“, William Cameron Chumlea et al, Pediatrics, 1 January 2003 — Abstract:
Concern regarding change in the onset of sexual maturation of US girls has increased the need for current information on age at menarche from a national sample. Previous reports have been sparse and interpretation has been limited because of the racial composition and ages of the samples.
The objectives of this study were to estimate the distribution of age at menarche for all US girls and for non-Hispanic white, black, and Mexican American girls in the Third National Health and Nutrition Examination Survey and to test for racial differences.
Menstrual status data were collected from 2510 girls aged 8.0 to 20.0 years. The Third National Health and Nutrition Examination Survey followed a complex, stratified, multistage probability cluster design. SUDAAN was used to calculate proportions of girls reaching menarche at an age. Ages at menarche were estimated by probit analysis at the ages at which 10%, 25%, 50%, 75%, and 90% of the girls attained menarche.
Less than 10% of US girls start to menstruate before 11 years, and 90% of all US girls are menstruating by 13.75 years of age, with a median age of 12.43 years. This age at menarche is not significantly different (0.34 years earlier) than that reported for US girls in 1973. Age at menarche for non-Hispanic black girls was significantly earlier than that of white girls at 10%, 25%, and 50% of those who had attained menarche, whereas Mexican American girls were only significantly earlier than the white girls at 25%.
CONCLUSION: Overall, US girls are not gaining reproductive potential earlier than in the past. The age at menarche of non-Hispanic black girls is significantly earlier than that of non-Hispanic white and Mexican American girls.
This does not disprove the larger theory that biologically active pollutants are affecting us and other life forms. For one example (with better foundation) see A serious threat to us – a top priority shockwave – a hidden danger (21 January 2009) — about Xenoestrogens.
Update: new research contradicting these findings
- “Early puberty in girls doubles in a decade“, New Scientist, 10 August 2010
- The study: “Pubertal Assessment Method and Baseline Characteristics in a Mixed Longitudinal Study of Girls“, Frank M. Bird et al, Pediatrics, 3 September 2010
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