Worldwide Secular Trends in Age at Pubertal Onset Assessed by Breast Development Among Girls: A Systematic Review and Meta-analysis

Camilla Eckert-Lind; Alexander S Busch; Jørgen H Petersen; Frank M Biro; Gary Butler; Elvira V Bräuner; Anders Juul

doi:10.1001/jamapediatrics.2019.5881

Research Methods · Evidence Synthesis

Worldwide Secular Trends in Age at Pubertal Onset Assessed by Breast Development Among Girls: A Systematic Review and Meta-analysis

Eckert-Lind C, Busch AS, Petersen JH, Biro FM, Butler G, Bräuner EV, Juul A

JAMA pediatrics, 2020

DOI 10.1001/jamapediatrics.2019.5881 PMID 32040143 PMC PMC7042934

RRM Academy Synopsis

Girls' breast development age fell almost 3 months a decade, 1977-2013

A systematic review and meta-analysis of 30 studies in healthy girls found that breast development began almost 3 months earlier per decade from 1977 to 2013. Most studies came from Europe or North America. Onset ages differed by region.

Key Findings

A search of PubMed and Embase found 3602 studies. The meta-analysis covered 30 studies that assessed breast development (Tanner breast stage 2) by clinical examination in healthy girls.
Age at onset of Tanner breast stage 2 decreased 0.24 years per decade (95% CI, −0.44 to −0.04; P = .02), almost 3 months, from 1977 to 2013.
In the 18 studies that described palpation of the breast, the decrease was 0.26 years per decade (95% CI, −0.49 to −0.02; P = .03), more than 3 months.
Median ages at onset ranged from 8.8 to 10.3 years in the United States, the earliest region, and from 10.1 to 13.2 years in Africa, the latest.
Analyses within each region separately had low statistical power, and their results were not significant.

Interpretation

The review pools published studies of healthy girls examined by trained pediatricians. A weighted regression relates each study's year to its average onset age. The result is an association between calendar year and onset age across populations. Most studies came from Europe or North America. The authors note that 35% of the included studies had fewer than 500 girls, which could affect precision. They conclude that the traditional definition of precocious puberty may be outdated in some regions.

RRM Context

Restorative reproductive medicine treats the ovulatory cycle as a vital sign. It follows reproductive health from the start of puberty. Breast development is the first sign of puberty, and the review found that its average onset age fell across studies from 1977 to 2013. Evaluation comes before treatment, so the ages seen as normal matter. Root-cause thinking asks why the timing shifted. The authors name body mass index and hormone-disrupting chemicals as possible factors.

Our editorial summary of this paper, not the article's abstract.

Abstract

Importance

The initial clinical sign of pubertal onset in girls is breast gland development (thelarche). Although numerous studies have used recalled age at menarche (first menstruation) to assess secular trends of pubertal timing, no systematic review has been conducted of secular trends of thelarche.

Objectives

To systematically evaluate published data on pubertal timing based on age at thelarche and evaluate the change in pubertal onset in healthy girls around the world.

Data Sources

A systematic literature search was performed in PubMed and Embase of all original peer-reviewed articles published in English before June 20, 2019.

Study Selection

Included studies used clinical assessment of breast development in healthy girls and used adequate statistical methods, including the reporting of SEs or CIs. The quality of the articles was evaluated by assessing study design, potential sources of bias, main characteristics of the study population, and methods of statistical analysis.

Data Extraction and Synthesis

In accordance with PRISMA guidelines, all articles were assessed for eligibility independently by 2 authors. Weighted regression analysis was performed using a random-effects model.

Main Outcomes and Measures

Studies examining age at thelarche (development of Tanner breast stage 2) in healthy girls.

Results

The literature search resulted in a total of 3602 studies, of which 30 studies fulfilled the eligibility criteria. There was a secular trend in ages at thelarche according to race/ethnicity and geography. Overall, the age at thelarche decreased 0.24 years (95% CI, -0.44 to -0.04) (almost 3 months) per decade from 1977 to 2013 (P = .02).

Conclusions and Relevance

The age at thelarche has decreased a mean of almost 3 months per decade from 1977 to 2013. A younger age at pubertal onset may change current diagnostic decision-making. 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.

Topics

Research Methods Evidence Synthesis Meta-Analysis

Research Methods › Evidence Synthesis › Meta-Analysis

Camilla Eckert-Lind, Alexander S Busch, Jørgen H Petersen, Frank M Biro, Gary Butler, Elvira V Bräuner, Anders Juul

C Eckert-Lind, Alex Busch, A Busch, J Petersen, F Biro, G Butler, E Bräuner, A Juul

PMID 32040143 32040143 DOI 10.1001/jamapediatrics.2019.5881 10.1001/jamapediatrics.2019.5881 Eckert-Lind et al. 2020, Eckert-Lind 2020

Worldwide Secular Trends in Age at Pubertal Onset Assessed by Breast Development Among Girls: A Systematic Review and Meta-analysis

Girls' breast development age fell almost 3 months a decade, 1977-2013

Key Findings

Interpretation

RRM Context

Abstract

Topics

By this author

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