American girls have had their first periods increasingly earlier over the past 50 years, according to a new study | united states news

Girls in the United States got their first periods earlier over the past five decades and took longer to experience regular cycles, a new study found.

The study, published in JAMA Network Open, found that the trend is especially pronounced among black, Hispanic, Asian and mixed-race participants, and among those who reported lower socioeconomic status.

“This is important because early menarche,” or a first period, “and irregular periods can indicate physical and psychosocial problems later in life,” said Zifan Wang, a postdoctoral researcher at the University’s TH Chan School of Public Health. from Harvard and lead author of the study.

Starting 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 they had their first period, when it became regular, and to obtain some demographic information. The researchers then divided the group into five generational groups.

They found that women born in the oldest age group, between 1950 and 1969, had their period at 12.5 years on average, compared to 11.9 years for the youngest group, born between 2000 and 2005.

The study was conducted through an app as part of the Apple Women’s Health Study. This has allowed researchers to check back with a group multiple times, or what researchers call a longitudinal study design.

Although the study was large, it is based on information provided by patients themselves, which is generally considered less reliable than sources such as medical or financial records. In some cases, it would have required participants to think back decades. Still, the study is likely to provide direction for future research.

In addition to a younger average age at menarche, the study found that the rate of people who had an early (under 11) or very early (under nine) first period approximately doubled between the oldest and youngest generations . For the oldest age group, 8.6% had their period before the age of 11, compared to 15.5% of people in the younger generation. Similarly, 0.6% of people in the older generation had a period before age nine, compared to 1.4% of the younger generation.

“We certainly see patients who have periods as early as nine or 10 years old,” said Dr. Anne-Marie Amies Oelschlager, a pediatric gynecologist at the University of Washington School of Medicine and president of the American College of Obstetricians and Gynecologists (ACOG). ) clinical consensus committee in gynecology.

He continued: “Although this is considered within the typical range, it is quite distressing for our patients and their parents. “They are still in elementary school in third or fourth grade, and trying to manage periods in third or fourth grade is difficult.”

It is important to note that menarche at younger ages may not be pathological. Amies Oelschlager said better hygiene and nutrition are likely at least part of the reason girls have earlier periods, both in the United States and around the world.

“If someone shows signs of puberty before age eight, they should talk to their doctor about it, and if they haven’t had a period by age 15, they should talk to their doctor about it, too,” he said. In some cases, very early puberty can be a sign of rare but serious diseases, such as brain tumors.

An early period can have lifelong implications. The onset of puberty fuses growth plates, meaning that people who hit puberty early may not reach their maximum genetic height. It can also raise women’s risk of cardiovascular disease and breast cancer.

Early physiological development can also have dramatic social impacts, because it does not coincide with early cognitive development. Children who experience early puberty are at increased risk of sexual violence, sexually transmitted infections, and early pregnancies.

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 is occurring in younger American girls, but more research will be needed to confirm that menarche occurs on average in girls younger than 12, as the new JAMA Network Open study suggests. .

Many factors influence the onset of puberty, but the exact reasons for menarche and breast development at younger ages are debated. One hypothesis is that a higher percentage of body fat causes the pituitary gland to produce puberty hormones. Other research has shown that body mass index is the greatest predictor of early menstruations. Scientists reason that a higher prevalence of childhood obesity may explain the higher proportion of girls having early periods.

“What we need to ask ourselves is why has (body mass index) increased?” Dr. Frank Biro, a physician at Cincinnati Children’s Hospital Medical Center, told Scientific American. “Decreased physical activity and a higher-calorie diet are probably part of the puzzle. But I think another key piece is our ubiquitous environmental exposure to endocrine-disrupting chemicals.”

Endocrine disruptors from plastics and petrochemical pollution are found in a wide range of consumer goods, including pesticides, construction materials, furniture, children’s toys, fabrics and cosmetics. Most remain unregulated despite warnings from scientists about possible negative effects on human health.

Wang said a wide range of factors need to be considered to understand why menarche may be happening in younger girls.

“These factors can include what’s in the environment, such as chemicals that affect hormones and air pollution, or dietary patterns, stress and adverse childhood experiences,” she said. “Studying these factors could help us find better ways to stop or slow these trends.”

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