FRIDAY, May 31, 2024 (HealthDay News) -- The mean age at menarche has decreased and time to cycle regularity has increased with increasing birth year, according to a study published online May 29 in JAMA Network Open.
Zifan Wang, Ph.D., from the Harvard T.H. Chan School of Public Health in Boston, and colleagues examined temporal trends and disparities in menarche and time to regularity and explored early-life body mass index (BMI) as a mediator. Data were analyzed from 71,341 female individuals.
The researchers found that from 1950-1969 to 2000-2005, the mean age at menarche decreased from 12.5 to 11.9 years. There was an increase observed in the number of individuals experiencing early menarche (younger than 11 years) from 8.6 to 15.5 percent and very early menarche (younger than 9 years) from 0.6 to 1.4 percent, while a decrease was seen in the number experiencing late menarche (age 16 years and older) from 5.5 to 1.7 percent. Of the 61,932 participants with reported time to regularity, there was a decrease in the number reaching regularity within two years, from 76.3 to 56.0 percent, while the number not yet in regular cycles increased from 3.4 to 18.9 percent. An exploratory mediation analysis estimated that BMI explained 46 percent of the temporal trend in age at menarche.
"These trends appeared across all sociodemographic groups but were stronger among certain racial and ethnic groups (Asian, non-Hispanic Black, or other and multiple races or ethnicities) and low subjective socioeconomic status groups," the authors write.
Two authors disclosed ties to Apple.
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