Noted: Researchers at the University of Wisconsin-Madison and the National Institutes of Health published their study late last month in the Proceedings of the National Academy of Sciences journal, in which they analyzed a total of 1.6 million menstrual cycles, using anonymized data self-reported through a smartphone app by 267,000 people.
They found 22% of the people in their study had menstrual cycles that vary by a week or more, a finding that is consistent with other research on the topic, said Jenna Nobles, a UW-Madison demographer who led the study. Nearly all the study’s subjects identified as women, she said.
“Less than 1% of cycles are 28-day cycles with day 14 ovulation, even though that is the stylized version of menstruation that we all learn about,” she said.
Nobles conducted the research with UW-Madison graduate student Lindsay Cannon and NIH emeritus investigator Allen Wilcox, who is a physician and a renowned scholar of reproductive epidemiology. Wilcox’s previous research has served as the foundation of knowledge around topics including when in the menstrual cycle people get pregnant and how likely it is that people will have miscarriages.