Endocrine Abstracts

JOINT368

Background: The mean age at thelarche has declined worldwide in recent decades. However, it is unclear whether this trend in the onset of puberty persists. Additionally, it remains unknown if there have been corresponding shifts in the upper and lower age limits (±2 standard deviations [SDs]) of pubertal onset.

Objective: To update published data on the secular trend in mean age at pubertal onset in girls and to evaluate the upper and lower age limits of pubertal onset over time.

Methods: This systematic review and meta-analysis updated a previous review from our research group(1) of 38 publications (1977–2019) by conducting an extended literature search in PubMed and Embase for original and peer-reviewed studies published between 2019 and 2024. The current study included the 38 publications from the previous study in the meta-analysis, with minor data updates. Studies reporting the onset of breast stage 2 (B2, thelarche) in healthy girls examined by healthcare professionals were included. Study quality was assessed based on study design and statistical methods. Global trends were calculated using weighted regression analysis.

Results: A total of 44 publications (six new) met the inclusion criteria, representing 60 populations and approximately 246,000 girls. The mean age at thelarche decreased by 0.26 (95% CI: -0.43 to -0.09) years (P = 0.002), corresponding to 3.1 months per decade. In 30 of the 44 publications, data on SDs was available. The upper age limit of thelarche decreased by 0.29 (-0.53 to -0.04) years (P = 0.02), corresponding to 3.5 months per decade, while the lower age limit decreased by 0.12 (-0.41 to 0.16) years (P = 0.40), corresponding to 1.5 months per decade.

Conclusion: Our worldwide study confirmed that marked changes continue in the mean age at thelarche. Importantly, we found a downward trend in the upper age limit of pubertal onset in girls, while the trend did not reach statistical significance for the lower age limit of pubertal onset. Although our results may not directly inform revised age limits for normal pubertal timing in all countries, they provide a global overview of secular trends. Further investigation is needed to determine the clinical implications.

Reference: 1. Eckert-Lind C et al. Worldwide Secular Trends in Age at Pubertal Onset Assessed by Breast Development among Girls: A Systematic Review and Meta-analysis. JAMA Pediatr. 2020. 174 (4): e195881.