Young girls are starting their first periods earlier than they have in previous decades—a shift associated with adverse health outcomes later in life. Researchers with the Harvard T.H.
Chan School of Public Health’s Apple Women’s Health Study examined data from more than 71,000 U.S. women born between 1950 and 2005, encompassing various ethnicities and socioeconomic backgrounds.
They aimed to determine the age at which these women experienced their first menstrual cycle and how long it took for their cycle to become regular. The study found that nearly 16 percent of women born between 2000 and 2005 started their menstrual cycles between ages 9 and 11, compared to almost 9 percent of those born between 1950 and 1969. Additionally, researchers observed an increase in the number of women experiencing irregular menstrual cycles for three years or more after menarche.
When stratifying trends by race and ethnicity, participants who were Asian, Hispanic, non-Hispanic black, or of other or multiple races or ethnicities were consistently more likely to experience early menarche than non-Hispanic white participants..
