Saturday 13 February 2010

biochemistry - Evolutionary origin and exogenous cues of ~28 day infradian rhythm?


A double-blind, prospective study during the fall of 1979 investigated
the association between the menstrual cycles of 305 Brooklyn College
undergraduates and their associates and the lunar cycles.



.... Approximately 1/3 of the subjects had lunar period cycles, i.e.
a mean cycle length of 29.5 ± 1 day. Almost 2/3 of the subjects
started their October cycle in the light 1/2 of the lunar cycle,
significantly more than would be expected by random distribution. The
author concludes that there is a lunar influence on ovulation.




(Menstrual and Lunar Cycles, Friedmann E., American Journal of Obstetrics and Gynecology, 1981)



Another source supports this conclusion, finding that "a large proportion of menstruations occurred around the new moon."



Somewhat related, this study found that light exposure shortened menstruation cycles.



In summary, there seems to be a good amount of data suggesting that lunar cycles do in fact calibrate the length of human menstrual cycles to some degree.

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