A recent meta-analysis has found that puberty in girls is starting a year earlier than it did a decade ago. In fact, the age of breast development in girls is declining three months per decade.
The meta-analysis, conducted at University of Copenhagen, Denmark, analyzed data of 30 studies conducted from 1977 to 2013. Dr. Alexander Busch, lead author and growth and reproduction researcher, combed and pooled medical literature to track age of breast development (thelarche) and puberty onset in girls.
They noticed a steady decline in the age of thelarche over the past four decades, from 1977-2013. The researchers could not put a finger on the exact cause of the decline but have voiced concerns over the decline and its repercussions. To quote Dr. Busch:
“There are not many studies out there concerning the implications of early breast development for women’s lifelong health. While interesting, these findings would have meant more if they’d been combined with other changes that come in puberty.”
What’s Causing Early Puberty In Girls?
Puberty is a stage of life when a child’s body changes as they transition into adulthood. It has different stages in both sexes, first being breast development and last being menstruation in girls. On the other hand, boys sprout facial hair and develop a deep voice. Years after the breast developing to firm, a teenage girl gets her first period (called menarche). Girls do get acne and begin gaining weight as their body begins to grow in shape.
Average age of thelarche varies throughout the world but falls in the safe window of 9-11 years. In the U.S. and Asia, girls develop breasts between 9-11 years; 10-11 in Europe; and 10-13 in Africa. However, breast development as early as 8 years or less is alarming, indicating puberty and hormonal disorders.
The meta-analysis reveals a constant decline in the age girls hit puberty, requiring for further study to reveal the exact pattern to define the trend and seek measures to prevent this decline as early-onset breast development and menstruation are indicators of several health complications later in life such as obesity, type 2 diabetes, heart disease and depression.
Dr. Busch pointed toward the fact that higher body mass index may be a contributing factor toward thelarche.
“Fat tissue is an important part of our hormone system, both in producing and metabolizing hormones,” he said. “Thereby, a higher age-specific BMI is contributing to early pubertal onset. But excess weight alone cannot explain this drastic shift.”
Other factors such as endocrine-disrupting chemicals (EDCs) may also contribute to early puberty in girls. EDCs such as bisphenol A are all around us and found abundantly in plastics. These mimic estrogen hormone in the body and signal onset of menstrual cycle.
Diet also plays an important role in hormonal changes in the body. A cross-sectional study assessed the association of diet and precocious puberty in children through a food frequency questionnaire. Height, weight, stages of breast development, pubic hair and testicular volume were measured. Three dietary patterns were named as “traditional diet”, “protein diet” and “unhealthy diet”. Traditional diet and protein diet showed no association with early puberty but an unhealthy diet showed a positive association with early puberty in children. The traditional diet included fruits, vegetables, protein, and normal fat whereas an unhealthy diet was high in desserts, sugar, fast and junk food.
Another study in rats showed that fat-rich diet could act as a stimulator for precocious puberty.