I saw something a little while ago debunking the syncing up thing.
Correct. It turns out to be a myth that women's periods automatically synch up.
No, women do not get matching menstrual cycles if they spend too much time together.
www.nytimes.com
****************************************************************
Short Take
There is no science to support the claim that menstrual cycles of women who live together or who otherwise spend a lot of time with each other sync up.
Tell Me More
The theory that menstrual cycles sync up for women who are nearby for extended periods has been around for quite some time, but the few studies that support the theory are of low quality. In addition, no one has been able to suggest a plausible mechanism for such syncing up to occur.
In 2017, the menstrual period tracking app Clue
evaluated data from its users to see if there was any link between menstrual cycle schedule and time spent together and found no association.
What about corroborating stories? Menstrual cycle length can vary from woman to woman, as well as be affected by a variety of factors, such as sleep, stress and fluctuations in weight. So the chances are two women who spend time together will have an occasional menstrual cycle that starts within one or two days of the other. Remembering these seemingly synced periods as a consistent trend rather than chance is recall bias. Women are probably less likely to take note of all the time they routinely spend in the close company of other women — spouses, partners, roommates, co-workers or friends — whose cycles do not coincide.
There are a variety of period tracking apps — Apple Watch
just debuted a new feature for menstrual cycle tracking. A
2016 reviewof apps on the market at the time found many were inaccurate or contained misleading health information. While these apps may allow for greater ease of entering and recalling data about cycles than a calendar (digital or paper), unless they have been cleared by
the Food and Drug Administration, relying on these apps as a health tool is a buyer (or user) beware situation.