A new study has found that girls in the United States have been experiencing their first period earlier over the past five decades and are taking longer to experience regular menstrual cycles.
The study, published in JAMA Network Open, found that this trend was particularly pronounced among Black, Hispanic, Asian and mixed-race participants and those who reported lower socioeconomic status.
“This is important because early menarche,” or first menstrual period, “and irregular menstrual periods may indicate physical and psychosocial problems later in life,” said Zifan Wang, a postdoctoral research fellow at Harvard University’s TH Chan School of Public Health and lead author of the study. study.
Beginning in 2019, researchers from Harvard and the National Institute of Environmental Health Sciences (NIEHS) surveyed more than 71,000 participants born between 1950 and 2005 about when their first period occurred, when it became regular, and certain demographic information. The researchers then divided the group into five generational groups.
They found that women in the oldest group born between 1950 and 1969 started menstruating at an average age of 12.5 years, while in the youngest group born between 2000 and 2005, it was 11.9 years old.
The research was conducted through an app as part of the Apple Women’s Health Research. This allowed researchers to check on a group multiple times, or what researchers call a longitudinal study design.
Although the study was large, it relied on self-reported information, which is generally considered less reliable than sources such as medical or financial records. In some cases, participants might have had to think back decades. Still, the study is likely to guide future research.
In addition to a younger average age at menarche, the research found that the proportion of people who had their first period early (under age 11) or very early (under age nine) roughly doubled between the oldest and youngest generations. While 8.6% of the oldest group had their period before the age of 11, this rate was 15.5% in the youngest generation. Similarly, 0.6 percent of people in the oldest generation had their period before the age of nine, compared with 1.4 percent of the youngest generation.
D., a pediatric gynecologist at the University of Washington School of Medicine and president of the American College of Obstetricians and Gynecologists (ACOG). “We definitely see patients who are menstruating as young as nine or 10 years old,” said Anne-Marie Amies Oelschlager. ) clinical consensus committee for gynecology.
He continued: “Although it is evaluated within the typical range, it is a very distressing situation for our patients and their parents. “They are still in third or fourth grade of primary school, and trying to manage their periods in third or fourth grade is very difficult.”
Importantly, menarche at younger ages may not be pathological. Better sanitation and nutrition are at least part of the reason why girls are menstruating earlier, both in the U.S. and globally, Amies Oelschlager said.
“If someone shows signs of puberty before the age of eight, they should talk to their doctor about this, and if they haven’t had their period by age 15, they should talk to their doctor about this as well,” he said. In some cases, very early puberty can be a sign of rare but serious conditions such as brain tumors.
An early episode can have lifelong effects. The onset of puberty brings the growth plates together; This means that people who enter puberty early may not reach their maximum genetic height. It may also increase the risk of cardiovascular disease and breast cancer in women.
Early physiological development can also have dramatic social effects because it does not coincide with early cognitive development. Children experiencing early puberty are at high risk for sexual violence, sexually transmitted infections, and early pregnancy.
Early puberty is also associated with an increased risk of depression, anxiety, substance abuse, and suicidal behavior.
Amies Oelschlager said the literature currently suggests that breast development occurs in young American girls, but more research will be needed to confirm that menarche occurs in girls younger than age 12, on average, as the new JAMA Network Open study suggests.
Many factors influence the onset of puberty, but the exact causes of menarche and breast development at younger ages are debated. One hypothesis is that a high body fat percentage triggers the pituitary gland to produce puberty hormones. Other studies have shown that body mass index is the biggest predictor of early menstruation. Scientists think that the higher rate of childhood obesity may explain why girls have a higher rate of early menstruation.
“What we have to ask is why? [body mass index] elevated?” Dr. Frank Biro, a physician at Cincinnati Children’s Hospital Medical Center, told Scientific American: “Reduced physical activity and a more calorie-dense diet are probably part of the puzzle. “But I think another critical point is our environmental exposure to endocrine disrupting chemicals everywhere.”
Endocrine-disrupting chemicals from plastics and petrochemical pollution are found in a wide variety of consumer goods, including pesticides, building materials, furniture, children’s toys, fabrics, and cosmetics. Many remain unregulated, despite warnings from scientists about their potential adverse effects on human health.
Wang said a wide variety of factors need to be taken into account to understand why menarche occurs in young girls.
“These factors may include chemicals that affect hormones and air pollution, or things in the environment such as dietary patterns, stress, and adverse childhood experiences,” he said. “Studying these factors can help us find better ways to stop or slow these trends.”