Among participants born from 1950-1969, the average age at menarche — the first occurrence of menstruation — was 12.5 years, the research shows.
“Among participants born from 2000-2005, the average age of menarche was 11.9 years, and the rates of early and very early menarche were 15.5% and 1.4%, respectively,” it says.
“The study found that as birth year increased (meaning younger participants), average age at menarche decreased and time from menarche to menstrual cycle regularity increased.”
The findings will help researches lead to a better understanding of menstrual health, and environmental impacts to the vital sign, according to co-principal investigator Shruthi Mahalingaiah, assistant professor of environmental, reproductive, and women’s health at Harvard Chan School.
Childhood obesity may also be a contributing factor — BMI at the age of menarche plays a role, the research report states.
“Other possible factors that might explain the trend include dietary patterns, psychological stress and adverse childhood experiences, and environmental factors such as endocrine-disrupting chemicals and air pollution,” the report states.
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