Early menstruation may cause adverse health problems later in life.
Young girls are starting their first periods earlier than they have in previous decades—a shift associated with adverse health outcomes later in life.
A new study published on May 29 in JAMA Network Open revealed that the median age at menarche has remained relatively stable at around 12 years, and the proportion of girls starting menstruation before age 11 has significantly increased over time.
Menarche, or the first menstrual period, marks the beginning of the monthly hormonal cycle and reproductive lifespan. Additionally, it signifies the end of female puberty.
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.
An exploratory analysis of a subset of 9,865 participants estimated that 46 percent of the trend could be attributed to body mass index—a measure of a person’s body fat based on height and weight. The authors noted that obesity is a risk factor for early-onset puberty and that childhood obesity is on the rise in the United States, which could explain the trend toward earlier menarche. However, it’s unknown to what extent changes in early BMI affect the trend. The underlying cause of the remaining 54 percent experiencing early menarche remains unclear.
By Megan Redshaw, J.D.
