Puberty is the phase in which a boy or a girl develops sexually, with physical changes such as hair loss, breast growth (thelarche) or the first menstruation (menarche) in the case of girls. Its onset has traditionally been around the age of 8 for girls and 9 for boys. When it arrives before these ages, it is considered precocious puberty.
While there was a time when precocious puberty was rare, numerous studies show that it is becoming more common. Although the causes are not clear and are currently under investigation, experts point to obesity, stress and exposure to certain chemical components as some factors that increase the probability of experiencing precocious puberty. With the advancement of this, a greater risk of suffering cardiovascular diseases, breast cancer, depression and anxiety is also attributed.
A systematic review and meta-analysis published in the journal JAMA Pediatría found that the age of onset of puberty – taking thelarche in girls as a reference in the last 4 decades – decreased by an average of almost three months per decade from 1977 to 2013. Conclusions of this result, the researchers highlighted the need to take this into account when making diagnostic decisions, as well as to redefine precocious puberty, since they consider that "its current definition may be out of date".
Another study looked at the age of breast development in Copenhagen, studying the age of breast development of more than 2,000 girls between 5 and 20 years of age. As results, they concluded that the onset of puberty occurred significantly earlier in 2006 compared to 1991. In addition, they pointed out that alterations in reproductive hormones and body mass index did not explain this change, so "factors may be involved still to date." identify".
The increase in precocious puberty is also supported by other research published in the American Academy of Pediatrics, where data from 17,077 girls were analyzed, of whom 9.6% were African-American and 90.4% white. This study found that 3% of African-American girls and 1% of white girls developed pubic or breast hair by age 3. The percentages increased to 27.2% and 6.7% respectively at 7 years. Additionally, by age 8, 48.3% of African-American girls and 14.7% of white girls had begun to develop.
At all ages, for every characteristic taken into account in the study, little African-American girls developed earlier than white girls. The mean ages of onset of breast development for African American and white girls were 8.87 years and 9.96 years, respectively. The first menstruation reached 12.16 years of age in African-American girls and 12.88 years of age in white girls, according to the aforementioned study.