Lead Author of Study on Girls and Periods: 'It Alarms Us'

Over the last 50 years, US girls are getting their periods earlier and not as regularly
By Kate Seamons,  Newser Staff
Posted May 29, 2024 4:03 PM CDT
Updated Jun 2, 2024 7:01 AM CDT
Lead Author of Study on Girls and Periods: 'It Alarms Us'
   (Getty Images / iamnoonmai)

If you've anecdotally heard American girls are getting their periods earlier than they did in decades past, you heard correctly. A study published Wednesday in JAMA Network Open surveyed 71,000 women who were born between 1950 and 2005. The researchers from Harvard and the National Institute of Environmental Health Sciences found the earliest group (born between 1950 and 1969) got their first period at an average 12.5 years of age, while the youngest group (born between 2000 and 2005) were 11.9 years old on average. Other findings:

  • The rate at which girls got their period early (younger than 11) increased from 8.6% to 15.5% between the oldest and youngest generations.
  • The rate at which girls got their period very early (younger than 9) increased from 0.6% to 1.4%.
  • For those women who reported time to cycle regularity, the number reaching regularity within 2 years dropped from 76.3% to 56.0%. ""This is also very concerning because irregular cycles are an important indicator of later-in-life adverse health events. It alarms us," lead author Zifan Wang of Harvard tells the Washington Post.
  • The magnitude of the trend toward earlier periods was greater among women who self-identified as Asian, non-Hispanic Black, or other or multiple races.

As for the why, Wang says "factors may include what's in the environment like chemicals that affect hormones and air pollution, or dietary patterns, stress, and adverse childhood experiences." Childhood obesity and higher body-mass indexes have also been cited as potential factors. "Studying these factors could help us find better ways to stop or slow down these trends," says Wang. Early puberty has been associated with a host of increased risks for sexual violence, early pregnancy, depression, anxiety, and substance abuse.

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The Guardian adds that despite the large size of the study, "it relies on self-reported information—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 will likely provide direction for future research." (More health study stories.)

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