Recent decline in age at breast development: the Copenhagen Puberty Study

Area of Science:

• Pediatric endocrinology
• Reproductive health
• Public health

Background:

• Recent publications indicate earlier breast development in girls, sparking global debate.
• Secular trend analyses are challenged by data comparability issues across studies.
• This study presents new European data collected systematically over a 15-year period.

Purpose of the Study:

• To investigate secular trends in pubertal development in European girls.
• To compare pubertal timing between girls from 1991-1993 and 2006-2008 cohorts.
• To explore potential hormonal and BMI influences on these trends.

Main Methods:

• A cohort of 2095 girls aged 5.6–20.0 years was studied in two groups: 1991 cohort (n=1100) and 2006 cohort (n=995).
• Evaluations included breast and pubic hair staging via palpation, height and weight measurements, and blood sampling for hormone analysis (estradiol, LH, FSH).
• Age distributions for pubertal stages and menarche were estimated for both cohorts.

Main Results:

• The mean estimated age for pubertal onset (Tanner breast stage 2+) was significantly earlier in the 2006 cohort (9.86 years) compared to the 1991 cohort (10.88 years).
• This difference persisted after adjusting for Body Mass Index (BMI).
• While reproductive hormone levels (FSH, LH) did not differ, estradiol levels were lower in 8- to 10-year-old girls in the 2006 cohort.

Conclusions:

• European girls born more recently exhibit significantly earlier breast development.
• Changes in reproductive hormones and BMI do not account for the observed earlier puberty.
• Unidentified factors likely contribute to the accelerated pubertal timing.