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

Jeanne F. Duffy, Sean W. Cain, Anne-Marie Chang, Andrew J.K. Phillips, Mirjam Y. Mun̈ch, Claude Gronfier, James K. Wyatt, Derk Jan Dijk, Kenneth P. Wright, Charles A. Czeisler

Research output: Contribution to journalArticle

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Abstract

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. We analyzed precise estimates of intrinsic circadian period collected from 157 individuals (52 women, 105 men; aged 18-74 y) studied in a month-long inpatient protocol designed to minimize confounding influences on circadian period estimation. Overall, the average intrinsic period of the melatonin and temperature rhythms in this population was very close to 24 h [24.15 ± 0.2 h (24 h 9 min ± 12 min)]. We further found that the intrinsic circadian period was significantly shorter in women [24.09 ± 0.2 h (24 h 5 min ± 12 min)] than in men [24.19 ± 0.2 h (24 h 11 min ± 12 min); P < 0.01] and that a significantly greater proportion of women have intrinsic circadian periods shorter than 24.0 h (35% vs. 14%; P < 0.01). The shorter average intrinsic circadian period observed in women may have implications for understanding sex differences in habitual sleep duration and insomnia prevalence.

Original languageEnglish (US)
Pages (from-to)15602-15608
Number of pages7
JournalProceedings of the National Academy of Sciences of the United States of America
Volume108
Issue numberSUPPL. 3
DOIs
StatePublished - Oct 13 2011

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Circadian Clocks
Sex Characteristics
Melatonin
Sleep Initiation and Maintenance Disorders
Circadian Rhythm
Body Temperature
Inpatients
Sleep
Temperature

All Science Journal Classification (ASJC) codes

  • General

Cite this

Duffy, Jeanne F. ; Cain, Sean W. ; Chang, Anne-Marie ; Phillips, Andrew J.K. ; Mun̈ch, Mirjam Y. ; Gronfier, Claude ; Wyatt, James K. ; Dijk, Derk Jan ; Wright, Kenneth P. ; Czeisler, Charles A. / Sex difference in the near-24-hour intrinsic period of the human circadian timing system. In: Proceedings of the National Academy of Sciences of the United States of America. 2011 ; Vol. 108, No. SUPPL. 3. pp. 15602-15608.
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Duffy, JF, Cain, SW, Chang, A-M, Phillips, AJK, Mun̈ch, MY, Gronfier, C, Wyatt, JK, Dijk, DJ, Wright, KP & Czeisler, CA 2011, 'Sex difference in the near-24-hour intrinsic period of the human circadian timing system', Proceedings of the National Academy of Sciences of the United States of America, vol. 108, no. SUPPL. 3, pp. 15602-15608. https://doi.org/10.1073/pnas.1010666108

Sex difference in the near-24-hour intrinsic period of the human circadian timing system. / Duffy, Jeanne F.; Cain, Sean W.; Chang, Anne-Marie; Phillips, Andrew J.K.; Mun̈ch, Mirjam Y.; Gronfier, Claude; Wyatt, James K.; Dijk, Derk Jan; Wright, Kenneth P.; Czeisler, Charles A.

In: Proceedings of the National Academy of Sciences of the United States of America, Vol. 108, No. SUPPL. 3, 13.10.2011, p. 15602-15608.

Research output: Contribution to journalArticle

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T1 - Sex difference in the near-24-hour intrinsic period of the human circadian timing system

AU - Duffy, Jeanne F.

AU - Cain, Sean W.

AU - Chang, Anne-Marie

AU - Phillips, Andrew J.K.

AU - Mun̈ch, Mirjam Y.

AU - Gronfier, Claude

AU - Wyatt, James K.

AU - Dijk, Derk Jan

AU - Wright, Kenneth P.

AU - Czeisler, Charles A.

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N2 - 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. We analyzed precise estimates of intrinsic circadian period collected from 157 individuals (52 women, 105 men; aged 18-74 y) studied in a month-long inpatient protocol designed to minimize confounding influences on circadian period estimation. Overall, the average intrinsic period of the melatonin and temperature rhythms in this population was very close to 24 h [24.15 ± 0.2 h (24 h 9 min ± 12 min)]. We further found that the intrinsic circadian period was significantly shorter in women [24.09 ± 0.2 h (24 h 5 min ± 12 min)] than in men [24.19 ± 0.2 h (24 h 11 min ± 12 min); P < 0.01] and that a significantly greater proportion of women have intrinsic circadian periods shorter than 24.0 h (35% vs. 14%; P < 0.01). The shorter average intrinsic circadian period observed in women may have implications for understanding sex differences in habitual sleep duration and insomnia prevalence.

AB - 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. We analyzed precise estimates of intrinsic circadian period collected from 157 individuals (52 women, 105 men; aged 18-74 y) studied in a month-long inpatient protocol designed to minimize confounding influences on circadian period estimation. Overall, the average intrinsic period of the melatonin and temperature rhythms in this population was very close to 24 h [24.15 ± 0.2 h (24 h 9 min ± 12 min)]. We further found that the intrinsic circadian period was significantly shorter in women [24.09 ± 0.2 h (24 h 5 min ± 12 min)] than in men [24.19 ± 0.2 h (24 h 11 min ± 12 min); P < 0.01] and that a significantly greater proportion of women have intrinsic circadian periods shorter than 24.0 h (35% vs. 14%; P < 0.01). The shorter average intrinsic circadian period observed in women may have implications for understanding sex differences in habitual sleep duration and insomnia prevalence.

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