Sex difference in the near-24-hour intrinsic period of the human circadian timing system

Jeanne F Duffy, Sean Cain, AnneMarie Chang, Andrew J Phillips, Mirjam Y Munch, Claude Gronfier, James K Wyatt, Derk Jan Dijk, Kenneth P Wright, Charles Czeisler

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342 Citations (Scopus)


The circadian rhythms of melatonin and body temperature are set to an earlier hour in women than in men, even when the women and men maintain nearly identical and consistent bedtimes and wake times. Moreover, women tend to wake up earlier than men and exhibit a greater preference for morning activities than men. Although the neurobiological mechanism underlying this sex difference in circadian alignment is unknown, multiple studies in nonhuman animals have demonstrated a sex difference in circadian period that could account for such a difference in circadian alignment between women and men. Whether a sex difference in intrinsic circadian period in humans underlies the difference in circadian alignment between men and women is unknown.
Original languageEnglish
Pages (from-to)15602 - 15608
Number of pages7
JournalProceedings of the National Academy of Sciences of the United States of America
Issue numberSUPPL 3
Publication statusPublished - 2011
Externally publishedYes

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