The age at which menstruation begins has been for decades 鈥� and a new study indicates that in the US, the trend isn鈥檛 slowing. What鈥檚 more, multiple factors are probably contributing to the problem, making it almost impossible to combat.
This is worrying, given that menstruating before age 12 is linked to an increased risk of conditions like heart disease and certain cancers, says at Columbia University in New York, who wasn鈥檛 involved in the new work. For instance, those who begin menstruating between 11 and 12 years old have an almost of breast cancer, on average, than those who start at age 13.
To compare the onset of menstruation, at Harvard University and her colleagues collected data via a smartphone app on more than 71,000 people living in the US who had experienced at least one menstrual cycle in their life. On average, participants born between 2000 and 2005 got their first period at 11.9 years old, significantly earlier than those who were born between 1950 and 1969, who began menstruation at age 12.5.
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The effect was even more pronounced in racial minorities and those from lower socioeconomic levels. For those born between 2000 and 2005, Black participants got their first period around 11.5 years of age and white participants just after age 12.
So what鈥檚 behind the trend? 快猫短视频s have previously pointed to soaring rates of childhood obesity as the primary culprit, since menstruation doesn鈥檛 occur until the body attains a certain amount of body fat. But this is only one piece of the puzzle. The researchers estimate that body mass index (BMI) at the time participants got their first period was responsible for only about 46 per cent of the difference in menstruation onset.
鈥淚 think it鈥檚 looking at it too simplistically if we just point the finger at obesity,鈥� says Houghton. 鈥淭he drivers are multi-level and complex.鈥�
Stress also may be playing a role. It can increase the levels of certain hormones called androgens, which fat tissue can then convert into oestrogen hormones that drive the onset of menstruation, says Houghton. However, it is unclear if stress levels in adolescents are on the rise. A 2018 survey from the found that people born in the US between 1997 and 2012 are more stressed than older generations 鈥� but that is only compared with older generations today, not when those adults were adolescents.
Another contributing factor could be chemicals known as endocrine disruptors, which are found in certain plastics, pesticides and other consumer products. These chemicals can disrupt, block or mimic naturally occurring hormones, potentially interfering with puberty.
Yet research on how these chemicals affect menstruation has been , and their impact also depends on the age at which people encounter these chemicals and their . For instance, high blood levels of chemicals classified as perfluoroalkyl and polyfluoroalkyl substances (PFAS), otherwise known as forever chemicals, have been associated with delays in menstruation 鈥� whereas medium levels are linked to earlier menstruation.
Houghton believes that all of these factors, and some still-unknown ones, probably interact with one another to lower the age of menstruation. This could explain why racial minorities are most affected. 鈥淎 lot of these factors are downstream consequences of structural racism and are disproportionally impacting racial and ethnic minorities,鈥� says Wang.
The numerous potential causes could also make it more difficult to counteract their effects. 鈥淚t would take so much parsing out because they are so intertwined. It鈥檚 going to be very difficult,鈥� says at the University of North Carolina at Chapel Hill. 鈥淏ut [the age] can鈥檛 just keep going down.鈥�
JAMA Network Open
