Menstrual cycle shortest and longest cycle lengths is considered very irregular. The average menstrual cycle lasts 28 days. The variability of menstrual cycle lengths is highest for women under 25 years of age and is lowest, that is, most regular, for ages 25 to 39. Subsequently, the variability increases slightly for women aged 40 to 44. The luteal phase of the menstrual cycle is about the same length in most individuals (mean 14.13 days, standard deviation 1.41 days) whereas the follicular phase tends to show much more variability (log-normally distributed with 95% of individuals having follicular phases between 10.3 and 16.3 days).
Menstrual cycle the two. The relationship is believed to be a coincidence. Light exposure does not appear to affect the menstrual cycle in humans. A meta-analysis of studies from 1996 showed no correlation between the human menstrual cycle and the lunar cycle, nor did data analysed by period-tracking app Clue, submitted by 1.5m women, of 7.5m menstrual cycles. Dogon villagers did not have electric lighting and spent most nights outdoors, talking and sleeping, so they were apparently an ideal population for detecting a lunar influence; none was found. In a number of countries, mainly in Asia, legislation or corporate practice has introduced