Sept 2025: A paper by Prof. Helfrich-Forster from Julius-Maximilians University of Würzburg, Würzburg, Germany, was published, showing that women’s menstrual cycles recorded before the introduction of light-emitting diodes (LEDs) in 2010 and the extensive use of smartphones significantly synchronized with the Moon, while those after 2010 coupled to the Moon mostly in January. 

 

Thanks to all the woman who shared their data with me! This data was included in the paper. 

 

Pay attention that Italian and Israeli women had, on average, a period that was ~1 day shorter than that of women living in the other countries. The authors suggested that this is due to higher light pollution!