Girls' Age At Puberty Has Declined Worldwide Since Late 1970s

Age at pubertal onset in girls as measured by breast development, or thelarche, has decreased nearly 3 months for every decade since 1977, according to a new review and meta-analysis.

Based on the findings, the standard cutoff of age 8 for pathologically early breast development may need to be reconsidered, Camilla Eckert-Lind of the University of Copenhagen in Denmark and colleagues report in JAMA Pediatrics.

"The medical community needs current and relevant data to redefine 'precocious puberty,' because the traditional definition may be outdated, at least in some regions of the world, and may lead to unnecessary brain magnetic resonance imaging in healthy girls," they write.

Most studies use age at menarche to investigate secular trends in timing of puberty, the authors note. Recent research has suggested that median age at thelarche, traditionally set at 11 years, may be declining, they add.

The authors identified 30 studies of age at thelarche, or development of Tanner breast stage 2, in healthy girls published in 1977-2013. Most girls included in the studies were in the normal range for BMI.

Clinical examination with palpation was implied in 12 studies and specified in 18. Most studies were from North America or Europe, although there were also studies including populations from the Middle East, Asia, and Africa.

Median ages at thelarche were 9.8-10.8 years in Europe; 9.7-10.3 years in the Middle East, 8.9-11.5 years in Asia, 8.8-10.3 years in the US, and 10.1-13.2 years in Africa.

Overall, age at onset of Tanner breast stage 2 declined by 0.24 years per decade, and by 0.26 years when the analysis was restricted to studies in which clinical exams with palpation were specified.

"Recent diagnostic practice includes brain magnetic resonance imaging in girls younger than 8 years with pubertal signs, and biochemical evidence of central hypothalamus-pituitary-gonadal axis activation," the authors write.

"However," they add, "a strict criterion of 8 years as the lower limit of normal puberty would imply that a large proportion of healthy girls would in fact need to undergo brain magnetic resonance imaging if they were referred for evaluation."

—Reuters Staff

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