Trend is especially pronounced among Black, Hispanic and Asian participants, and those who report lower socioeconomic status

Girls in the United States had their first periods earlier over the last five decades and it took longer to experience regular cycles, a new study has found.

The study, published in JAMA Network Open, found the trend is especially pronounced among Black, Hispanic, Asian and mixed race participants, and among those who reported lower socioeconomic status.

“This is important because early menarche,” or a first period, “and irregular periods can signal physical and psychosocial problems later in life,” said Zifan Wang, a postdoctoral research fellow at Harvard University’s TH Chan School of Public Health and lead author of the study.