A study led by researchers at Harvard T.H. Chan School of Public Health has found that the average age at menarche, the first menstrual period, has been decreasing among younger generations in the U.S. This trend is especially pronounced among racial minorities and lower socioeconomic statuses. The study also found that the time it takes for the menstrual cycle to become regular is increasing. The findings will be published in JAMA Network Open and are part of the Apple Women’s Health Study, which focuses on menstrual cycles, gynecological conditions, and overall women’s health.
Previous studies have shown a trend towards earlier menarche over the past decades, but data on how these trends vary among different racial and socioeconomic groups has been limited. The researchers utilized a large and diverse dataset from the Apple Women’s Health Study to fill this research gap. They analyzed data from 71,341 participants across five different age brackets to determine trends in menarche age and time to menstrual cycle regularity. The study found that as birth year increased, the average age at menarche decreased, and the time from menarche to menstrual cycle regularity increased.
The study identified that BMI at the age of menarche could partially explain the trend towards earlier menarche, suggesting that childhood obesity may be a contributing factor to this phenomenon. Other potential factors include dietary patterns, psychological stress, adverse childhood experiences, and environmental factors like endocrine-disrupting chemicals and air pollution. The researchers emphasized the importance of continuing to investigate early menarche and its drivers, as early menarche is associated with higher risks of adverse health outcomes, such as cardiovascular disease and cancer.
The authors noted some limitations to the study, such as reliance on retrospective self-reporting. Despite these limitations, the study provides valuable insights into trends in menarche age and menstrual cycle regularity among different demographic groups. The findings suggest a need for further research and investment in menstrual health to address potential health concerns associated with early menarche, particularly among disadvantaged populations. The study was made possible through funding from Apple, Inc. and the National Institutes of Health, and included contributions from researchers at Harvard Chan School such as Gowtham Asokan, Jukka-Pekka Onnela, Michelle Williams, Russ Hauser, and Brent Coull.