Seasonal behavior of human menstrual cycles: a biometric investigation

N. Sundararaj, M. Chern, L. Gatewood, L. Hickman, R. McHugh

Research output: Contribution to journalArticlepeer-review

31 Scopus citations


Menstrual histories representing 38,194 woman-years were analyzed for seasonal periodicities using a simple additive model incorporating a secular trend. A recurrent sinusoidal pattern for cycle length was found which varied by 0.08 days throughout the year, decreasing during the warmer days of spring and summer, and increasing in the fall. Seperate analyses of cycle variability and numbers of cycles indicated similar results but without as clear an effect. Although these variations were statistically different from random deviations occurring during the year, they were not large enough to indicate any physiological relationship.

Original languageEnglish (US)
Pages (from-to)15-31
Number of pages17
JournalHuman Biology
Issue number1
StatePublished - 1978
Externally publishedYes


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