Why Kids Are Getting Their Periods Earlier and More Unpredictably Than Before, Study Reveals

Researchers examining menstrual cycles have identified several reasons why girls may experience early onset of menstruation. A recent study has revealed that children are beginning their periods at an earlier age, and the time it takes for their cycles to become regular is also changing.

These findings were published in the journal JAMA Network Open in May, 2024.

The data for this research was sourced from the Apple Women’s Health Study. The study involved researchers from the Harvard T.H. Chan School of Public Health and the National Institute of Environmental Health Sciences (NIEHS), with participation from the tech company Apple.

By analyzing menstrual cycle data from 71,341 individuals using iPhones and Apple Watches, researchers discovered that girls born between 2000 and 2005 are getting their first period at around 11.9 years old. In contrast, those born between 1950 and 1969 began menstruating at around 12.5 years old. The study highlights a decreasing trend in the age of first menstruation over generations, suggesting potential shifts in factors influencing the timing of puberty.

These trends may contribute to the increase in adverse health outcomes and disparities in the U.S.

People in the study who identified as Asian, non-Hispanic Black, or multiracial reported getting their first period at an earlier age compared to White participants. Dr. Zifan Wang, the lead researcher, noted that younger generations, from 1950 to 2005, are starting their first period earlier and that it takes longer for their periods to become regular, according to the findings.

Dr. Wang mentioned that this is important because starting periods early and having irregular ones can indicate potential health problems later in life, which need attention. He also emphasized that these changes might lead to more health issues and differences in the U.S. This highlights the significance of understanding and addressing these trends for public health purposes.

The researchers involved in the study indicated that early onset of menstruation could occur due to a variety of reasons.

They pointed out that being overweight is a risk factor for starting puberty early, suggesting a potential link between obesity and early onset of menstruation. Given the increasing prevalence of overweight children in the U.S., they hypothesize that obesity might contribute to the trend of girls starting their periods earlier.

Furthermore, the researchers highlighted other factors that might affect the timing of puberty, including environmental influences, dietary habits, stress, and adverse childhood experiences. These factors could play a role in the observed changes in the age of menstrual onset and warrant further investigation.

Researchers also found that body weight at the time of menarche plays a significant role in this trend.

Understanding the importance of early menarche and its association with health issues is crucial. While earlier menarche trends have been noted in the US, there’s limited data on differences based on sociodemographic factors and body mass index (BMI). Additionally, the time from menarche to cycle regularity is another aspect with health implications that hasn’t been studied much.

The results indicated a decline in the average age at menarche over time, with an increasing number experiencing early menarche and fewer achieving regularity within two years. This trend toward earlier menarche was particularly pronounced among certain racial and ethnic minority groups as well as individuals from low socioeconomic backgrounds.

Exploratory analysis indicated that BMI (Body Mass Index) accounted for a substantial portion of the observed temporal trend in age at menarche. These findings underscore potential factors contributing to adverse health outcomes and disparities in the U.S. associated with puberty timing.

Take a look at our other article featuring the athlete who experienced menstruation during a race, and explore the internet’s response to the incident.