Last month a new study was published with an attention grabbing title 'periods most often start on Thursday and Friday'. The results of this 7 day rhythmicity of menstruation came from analysing 311,064 cycles from 35,940 anonymous users of the Natural Cycles tracking app over 3 years.
The Natural Cycles Research Team had wanted to investigate:
when periods started in relation to the week, Monday through to Sunday
when periods started in relation to the lunar month i.e. the different lunar phases including new moon and full moon
On the instagram link to their research, Natural Cycles put the two key takeaways as:
"a weekly rhythm linked to menstruation, where periods most often start on a Thursday or Friday;
lunar rhythm also affects menstruation to a much smaller degree, with periods most often starting in the phases around the full moon"
Inspired, I decided to plot the weekday and lunar phase against my own last 7 years worth of cycle tracking (84 cycles). I adore cycle tracking and love a good spreadsheet of period data as well as using all the other creative ways I cycle track. Yet I didn't have the weekday or lunar month plotted against my start dates, so I was delighted for an opportunity to geek out further! Some quick additions to my spreadsheet showed me:
My bleed is most likely to start on a Monday or Sunday
A third of my bleeds come within 2 days of a new moon
Ok, so not quite the person that Natural Cycles identified in their data!
This reminded me about two things:
To always have a critical eye on new studies and be wary of sensational headlines in the news. When you delve further into the study, a smaller subset of 4,607 menstruators had provided information on 15 or more menstrual cycles (15-48 cycles, i.e. data showing at least a year's worth or data or up to a full 3 years). Whilst I'm so glad female bodies are being studied these days, we still need larger data sets over larger timespans and need to be conscious of who the data is gathered from and how
To track and engage with your own menstrual data, trusting and being with your own body over what others might be experiencing. I like how the Red School calls this 'The Big Red Rule': stay loyal to your cycle experience.
I'm grateful that the study inspired me to start tracking weekday and lunar phase against the date my bleed starts. I look forward to looking at my data in another 7 years time to see what new patterns might have emerged, knowing what I know now.
Here are some visuals of the last 7 years / 84 cycles:
Or to view another way...
So Thursday is the least likely day my period starts and I have twice the number of bleeds starting on a Monday than I do a Thursday.
And in regards to the lunar rhythm, this graph below shows the likelihood of my period starting with 2 days of the new or full moons and at other times over the lunar month.
When the timespan is enlarged to starting my period within 5 days of the full or new moon, then I've been synced more closely to the new moon than any other time.
So fun and games tracking one's own experience to the nth degree! And hallelujah for more research being done on women and our bodies.
Not quite sure yet how I'll use the info gleaned... open to ideas! I guess with a lot of public holidays falling on a Monday, and being self-employed where menstrual leave is mandatory, seems I might have a good portion of weeks in my years ahead starting exceptionally well.
Holding it all quite lightly for now! 😜
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