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Girls are getting their periods earlier and regularity is changing, according to a new study

Researchers looked at health data which over 71,000 women born between 1950 and 2005 self-reported on their iPhones and Apple watches.
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New research shows girls are getting their first period earlier, and cycles are taking longer to become regular — especially Black and Asian children and those with lower socioeconomic status. That’s according to a study published Wednesday in the Journal of the American Medical Association.

Researchers looked at health data which over 71,000 women born between 1950 and 2005 self-reported on their iPhones and Apple watches.

The oldest women — currently 55 to 70 years old — started their period when they were 12 1/2 years old on average. The youngest women, now in their late teens and early 20s, started at age 11, just shy of their 12th birthday.

Researchers also found it’s taking longer for cycles to become regular. Board-certified gynecologist Dr. Lillian Schapiro, who was not part of the study, says that can lead to health risks later in life.

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“They’re being exposed to estrogen internally, because they’re ovulating and having periods. Long exposure to estrogen has been shown to increase endometrial cancer and breast cancer,” said Dr. Schapiro.

The study says childhood obesity may be to blame for earlier periods. Dr. Schapiro says the period trends back up what doctors have seen in clinical practice.

“We’re seeing girls getting their period earlier because they are less healthy, because they have less access to healthy lifestyles and healthy diets,” Schapiro said.

Researchers aren’t sure about the causes, and are looking into what role environmental factors such as high-sugar diets or stress play in earlier periods.

Meanwhile, Schapiro suggests healthy diets full of fruits and veggies, fewer fried foods, and 20 minutes of movement or exercise daily for girls.