Children are starting menstruation earlier, a study shows. Here’s what this means for their health

"Among those born between 1950 and 2005, we found that younger generations had their first menstruation earlier, and the time needed for their menstruation to become regular also increased", said the study’s lead author, Dr. Zifan Wang, a postdoctoral researcher at Harvard University's T.H. Chan School of Public Health, reports CNN.

The study, published on May 29 in JAMA Network Open journal, analyzed data from over 70,000 participants who completed surveys as part of the Apple Women's Health Study, a long-term analysis of menstrual cycles using data from the Apple Health mobile app.

The data was collected digitally, relying on people's self-reported information based on their memories of early menstruation, thereby limiting the results, Wang said. However, other research has documented the trend of having first menstrual cycles at younger ages over time.

In the most recent study, researchers compared trends regarding the ages of first menstruation and how long it took for menstruation to become regular across age groups, Wang said. They found that the trends were even stronger for those from racial and ethnic minority groups and/or lower socioeconomic status.

"This is important because early menarche and irregular menstruation can signal physical and psychosocial issues later in life", Wang said, "and these trends may contribute to increasing negative health outcomes and disparities in the U.S".

Menstruation is like a vital sign, said Dr. Eve Feinberg, associate professor of obstetrics and gynecology at the Feinberg School of Medicine at Northwestern University in Chicago.

"You want to make sure the body is okay", Feinberg said. "And when cycles are not regular, it is generally a sign that something else might be happening".

Scientists and healthcare providers already know that early menstruation and a longer time for cycles to regulate are associated with negative health effects, including cardiovascular disease and cancer, Wang said.

As young women have irregular menstrual cycles, they are more exposed to an imbalance between two important hormones: estrogen and progesterone, Feinberg said.

Estrogen signals growth, while progesterone signals that this growth should stop, she added. To prevent conditions like uterine cancer, you need signals for both starting and stopping growth.

Theoretically, longer exposures to estrogen without a good balance of progesterone could increase the risk of endometrial cancers and fertility issues in the future, she said.

And early menstruation itself can pose problems, Feinberg added.

Earlier menstruations could be associated with a high body mass index, or BMI, during childhood, Wang said.

"This implies that childhood obesity, which has been increasing in the U.S., could contribute to people starting menstruation earlier", Wang added.

The cause could also be other environmental factors, such as nutrition or the prevalence of microplastics, Feinberg said, adding that more investigation is needed.

Further research can help doctors better counsel people about their menstruation and recognize the impact on their patients' health, said one of the main researchers of the study, Dr. Shruthi Mahalingaiah, assistant professor of environment, reproduction and women's health at Harvard’s T.H. Chan School of Public Health.

Doctors should evaluate children with early menstruation or long durations of irregular cycles to ensure there is no underlying problem, Feinberg said.

"Sometimes, even the use of contraceptive pills at an earlier age to help with earlier exposure to progesterone ... can provide a little more control over the cycle and may be potentially protective", she said. "But I think the key is probably to truly understand what drives this and get to the root cause".