Photo by Yustinus Tjiuwanda on Unsplash.

The average age of the onset of puberty in girls worldwide has dropped by a year or more over the past few decades, according to a meta-analysis of 30 studies published in 2023. The analysis showed that development of breast tissue, followed somewhat later by menarche (when a girl gets her first period) decreased by three months per decade from 1977 through 2013.

Increase in early menarche

A new study published by the Journal of the American Medical Association confirms the trend and shows that the number of girls experiencing “early menarche”, defined as prior to the 11th birthday, has doubled from 8 to 16 percent over that time period. Development of breast tissue has been seen in girls as young as seven years old.

The JAMA report tracked over 70,000 women who self-reported the age at which menstruation began and found that between 1950 and 1969 the average age of menarche was 12.5 years, and that between 2000 and 2005 that number had decreased to 11.9, with the number below 9 years more than doubling.

Health and social implications

Girls who develop earlier are out of sync with their peers.

Doctors and scientists are concerned for many reasons as early onset of puberty is related to serious health issues as well as numerous social and mental health problems.

Puberty begins in the brain when the hypothalamus and the pituitary gland secrete hormones signaling the ovaries to release estrogen and progesterone causing the body to make breast tissue, begin menstruation, and create the body shape changes of adolescence.

The trend is concerning to doctors and scientists because of the long-term implications of compromised women’s health, and the more immediate mental health issues girls experience when their 9-year-old body starts to act like a teenager, both physically and emotionally. Girls who develop earlier are out of sync with their peers and often the early growth results in shorter stature when growth then ceases early as well.

Correlations and contributing factors

There is growing evidence indicating that precocious puberty is linked to childhood obesity.

The study also showed a correlation between early puberty and stress, childhood trauma, and economic hardship. Research has shown that these girls suffer from depression and anxiety, poor body image, and emotional dysregulation more frequently than their peers. They experience more bullying and are often confused by expectations from adults that they act the age they appear to be rather than their actual age.

There is growing evidence indicating that precocious puberty is linked to childhood obesity, estimated to now be at the alarming rate of 20 percent in the US. Body fat is known to secrete hormones that affect appetite and the sense of satiety and might possibly trigger the earlier release of puberty-signaling hormones in the brain. Stress and obesity team up in a vicious cycle. Stress increases levels of cortisol and androgen hormones, and fat tissue converts these hormones to estrogen, which triggers early puberty.

A Chinese study showed that among children who ate three different diets, traditional, high protein, and unhealthy (highly processed, high fat and sugar, empty calories), the children who ate the unhealthy diet began puberty sooner.

The causes of childhood obesity are well-documented. A more sedentary lifestyle, excessive consumption of junk food and super-sized portions have all contributed to the uptick in overweight kids, many times leading to related metabolic disease in adulthood in all genders.

Girls living in areas with high levels of air pollution have also been shown to start puberty earlier.

In addition to obesity, there are environmental factors associated with early puberty. Endocrine-disrupting chemicals (EDCs) change the way our hormones work and trick the body into releasing puberty chemicals too soon. EDCs are everywhere, from food packaging to plastic toys, to meat and dairy products. Young girls, precociously asking and being permitted to wear makeup, are getting an extra dose of EDCs as cosmetics are full of them.

Girls living in areas with high levels of air pollution have also been shown to start puberty earlier.

The long-term health implications of early puberty are many. Studies link early onset of menstruation (before age 12) with a 20% increased risk of breast cancer. Scientists believe an increase in the occurrence of breast cancer, already occurring at a rate of as many as one in seven women, could be on the horizon as girls who have started their periods early in recent years reach adulthood. Early puberty is also associated with ovarian and endometrial cancers, cardiovascular disease, obesity, miscarriage, and early death.

Another factor in the trend is that girls, whenever their period starts, take longer to get to a stage of regularity in their cycles. Irregular cycles are linked to the formation of ovarian cysts.

Parental guidance and mitigation strategies

What is a concerned parent to do? If your daughter is experiencing early signs of puberty, with breast development usually being the first sign, take her to a qualified provider. It is important to rule out a brain issue which could be affecting the normal schedule of hormonal changes or to identify specific treatable conditions involving extremely premature or irregular growth patterns. If she is overweight, great care must be taken to bring her to a healthy body weight without fat-shaming or otherwise compromising her body image.

Dietary changes adding fruits and vegetables, limiting dairy and meat, and avoiding junk food are essential. Increased physical activity as well as reduced screen time will encourage weight loss, reduce stress, and encourage better sleep habits. Avoidance of plastics in all forms, and saying no to cosmetics will limit exposure to EDCs. Age-appropriate education and setting good examples can help the whole family achieve better health now and into the future.

Let your daughters know that we are all in this together and that their well-being is a non-negotiable value.

Ann Constantino, submitted on behalf of the SoHum Health’s Outreach department.