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Everyone has heard the phrase, "They grow up so fast," often cited by people who would like to see kids be kids for a little bit longer. However, scientific evidence suggests that children have gradually been reaching puberty at a younger and younger age for decades now. Children truly are growing up faster.
"There's been a trend in the last few decades of decreasing age of onset for puberty and a first period," says Kathleen Timme, MD, a pediatric endocrinologist at University of Utah Health. "Since the 1960s, each decade has seen a drop of about two to three months in the average age of a first period. And, if we are thinking about breast development, which is the first sign of puberty in girls, there has been a drop of about three months per decade in the average age from the 1970s to now."
Based on those trends, the average age for a girl to reach puberty has dropped about four years since the 1920s from the early high school years into more traditional elementary or middle school age groups.
Periods typically happen about two years after breast development, so 10 years or less is on the early side for girls. The average age for periods to begin for girls today is about 12 or 12 ½.
–Kathleen Timme, MD,
"We are currently defining precocious (or early) puberty in girls as any breast development before the age of 8," Timme explains. "Periods typically happen about two years after breast development, so 10 years or less is on the early side for girls. The average age for periods to begin for girls today is about 12 or 12 ½."
Now, a series of respected studies and reports shows a concerning uptick in the number of early or precocious puberty cases worldwide, especially during the pandemic.
"A decent body of literature from Italy, Germany, Lebanon, Turkey, and a study published by the San Diego pediatric endocrinology group shows an increase in early puberty cases and referrals along with diagnosis of precocious puberty that requires treatment," Timme says. "So, it is a trend that has been noticed across the world but not necessarily in my individual practice."
This continuing decline in the average age of puberty and the age below which doctors warn parents and guardians to be concerned has sparked a good deal of debate. Most focused on two questions: Why are our children reaching puberty at earlier and earlier ages, and what are the physical, social, and mental implications?
Timme cites several hypotheses about why this is happening. "We know that a lot of timing of puberty is determined by genetics," she says. "About 70% of pubertal timing and tempo is related to genetic factors."
She also emphasizes environmental factors, including obesity. "Certain hormones are made by the fat cells in our body, including leptin, which plays a role in starting puberty hormone secretions from the brain. The obesity epidemic in the last several decades can partially explain why puberty is happening earlier."
Pediatric endocrinologists like Timme have also observed that kids are sitting a lot more due to a sedentary lifestyle that includes extended use of electronic devices and TV time and less time playing outside and engaging in physical activity.
"Exercise triggers certain hormones that can delay the secretion of puberty hormones from the brain," Timme says. "Without that important exercise, there's a lack of inhibition to starting puberty, which could be another reason why it's happening earlier."
Add stress to the mix of factors, along with endocrine disruptors or chemicals in the environment that act upon hormones to interrupt their normal function, and it's not surprising that puberty is arriving earlier. What worries Timme and other medical professionals are the higher physical, mental, and social risks facing children who go through early puberty, sometimes in elementary school.
"A certain amount of maturity is required to handle the hygiene of a period and physical developments that might be different than your peers," Timme says. "Understanding who this child is, how they see themselves, and how they feel about their body changes is important." She stresses support and understanding from those caring for the child because early puberty has been associated with higher rates of anxiety, depression, eating disorders, and substance abuse.
Timme also emphasizes an understanding of how the child adjusts to adverse circumstances. "Age plays a big role," she says. "There's a huge difference between a 6-year-old going through puberty and an 8-year-old going through puberty and understanding where they are at developmentally." These are not adults or even young adults, which poses another dilemma.
"Early pubertal development is also associated with the concept of adultization," Timme says. "That can happen when young children have a body that is more typical of an older adolescent, where they are treated differently than peers. Those expectations can lead to complications in their school and social environments." She adds that precocious puberty can also be associated with earlier sexual activity.
While researchers and pediatricians seek better answers and understanding of the causes and long-term effects of early puberty, Timme encourages parents and guardians to be aware of changes in their children.
"Some of these changes can be subtle," she says. "Girls having periods is obviously a big milestone, but the first sign of puberty in girls is breast development. Sometimes families just don't quite realize what's going on until there are other signs of puberty like body hair, body odor, and periods."
In the end, it is up to families, in consultation with their doctors and medical team, to decide when a child is too young to go through puberty. "There are definitely times when we recommend and prescribe medications to pause puberty," says Timme, citing psychological and social concerns along with some serious physical issues.
"One of the big ones we worry about is the impact on final adult height. The puberty hormone estrogen is what causes growth plates to close." If a child goes through puberty at age 6 or 7, they may be tall for their age but then stop growing rather quickly and end up at an adult height well below what might be expected for their family.
Like any part of childhood, puberty is a stage and not the end of the journey. But the age when a child goes through this stage can have lifelong implications.
"Early puberty has associations with earlier heart disease, Type 2 diabetes, and breast and uterine cancer," Timme says. Laying the groundwork for healthy adulthood is always the goal, so better understanding and treatment of early puberty needs to be an essential part of securing a strong foundation for every child's future.
