Girls are starting to menstruate earlier and their cycles are taking longer to become regular than in previous decades, according to a recent peer-reviewed study.
The trend disproportionately affects people who are non-Hispanic Black, Asian, or of other or multiple races, although the authors say the reason is not clear.
But one explanation may be racial disparities in chemical exposures, which have been linked to early onset menarche – a girl’s first period.
The research was conducted by scientists from the Harvard T.H. Chan School of Public Health, the National Institute of Environmental Health Sciences and Apple.
Authors used data collected from the Apple Women’s Healthy Study of over 70,000 women born between 1950 and 2005. The number of individuals experiencing early menarche during those years nearly doubled, from about 9 percent in 1950 to 16 percent in 2005.
This is also the first study to report that individuals are taking longer to have regular menstrual cycles. The number of individuals who reached cycle regularity within two years decreased from 76 percent in 1950 to 56 percent in 2005.
The findings echo similar research elsewhere, including in Japan.
Early menarche has been linked to poor health outcomes, including worse cardiometabolic health, decreased fertility, breast cancer, and in extreme cases, increased rate of mortality.
Link to toxic chemical exposures
Many chemicals can affect the beginning of menstruation, including endocrine-disrupting chemicals, which can alter the normal function of hormones.
The toxic “forever chemicals” known as PFAS are among these substances, as are phthalates and phenols, which people are commonly exposed to from air pollution, contaminated drinking water, in their diet, and personal care products. One theory is that young girls’ exposure to these chemicals through their daily lives could be linked to menstruation starting earlier.
Another possible reason for the trend toward earlier and earlier onset of menstruation is childhood obesity, the study says, but that factor does not completely explain this trend.
Reducing chemical exposure
Chemicals of concern are everywhere, so avoiding them completely is impossible. But there are still steps adults and children alike can take to lower their exposures and health risks:
- EWG offers resources for safer products to reduce exposure to chemicals, including those that disrupt the hormone system. Use EWG’s Healthy Living App, Skin Deep® and Guide to Healthy Cleaning and look for products with low hazard scores or our EWG Verified® mark.
- Consult the EWG Tap Water Database to find out which contaminants might be in your drinking water. EWG’s water filter guide can help you find the right filter for your budget.
- Shop organic whenever possible. EWG Shopper’s Guide Pesticides in Produce™ lists the fruits and vegetables with the highest and lowest pesticide residues, so consumers can make the best decisions for their families.
