ArticleProceedings of the National Academy of Sciences of the United States of America2011
Sex difference in the near-24-hour intrinsic period of the human circadian timing system.
Article in Proceedings of the National Academy of Sciences of the United States of America, 2011. The graph could read no effect estimate from its abstract, so it casts no vote on the map. Cited by 309 papers, 2 of them syntheses that pooled it.
What it found
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The abstract states no effect estimate the extractor could read, or names no intervention and outcome on the map, so this paper lights no cell and moves no belief. It is still indexed, cited and linked below.
The trial behind it
Trials whose registry record cites this paper, or whose number appears in the abstract. A trial that started after this paper was published is citing it as background, not reporting it.
Neither the registry nor the abstract names a trial number. If this is a trial report, that itself is worth knowing.
Who cites it
309 citing papers in PubMed, 2 syntheses or guidelines pooled it.
- Circadian realignment and depressed mood: A systematic review.Sleep medicine reviews · 2025Pooled it
- Disrupting the clock: meta-analysis of irregular night shifts and migraine, proposing shift work migraine disorder with chronobiology strategies.Frontiers in neurology · 2025Pooled it
- Resetting of the Human Circadian Melatonin Rhythm by Ambient Hypoxia.Journal of pineal research · 2025Trial
- Low-dose exogenous melatonin plus evening dim light and time in bed scheduling advances circadian phase irrespective of measured or estimated dim light melatonin onset time: preliminary findings.Journal of clinical sleep medicine : JCSM : official publication of the American Academy of Sleep Medicine · 2024Trial
- Leveraging Ecological Momentary Assessment to Examine Bi-directional Associations Between Sleep Quality, Adolescent/Young Adult Alcohol Craving and Use.Annals of behavioral medicine : a publication of the Society of Behavioral Medicine · 2023Trial
- High dose melatonin increases sleep duration during nighttime and daytime sleep episodes in older adults.Journal of pineal research · 2022Trial
- Chronic Circadian Disruption and Sleep Restriction Influence Subjective Hunger, Appetite, and Food Preference.Nutrients · 2022Trial
- Identification of a Preliminary Plasma Metabolome-based Biomarker for Circadian Phase in Humans.Journal of biological rhythms · 2021Trial
- Efficacy of intermittent exposure to bright light for treating maladaptation to night work on a counterclockwise shift work rotation.Scandinavian journal of work, environment & health · 2021Trial
- Impact of Dim Light at Night on Urinary 6-Sulphatoxymelatonin Concentrations and Sleep in Healthy Humans.International journal of molecular sciences · 2020Trial
- Sex-dependent least toxic timing of irinotecan combined with chronomodulated chemotherapy for metastatic colorectal cancer: Randomized multicenter EORTC 05011 trial.Cancer medicine · 2020Trial
- Chronic exposure to artificial light at night dampens rhythms in locomotor activity, metabolism, and sleep in female mice.Physiology & behavior · 2026Article
- Circadian timing does not modulate human temporal contrast sensitivity.Journal of vision · 2026Article
- Nocturnal peak in cardiac baroreflex effectiveness aligns with nocturnal trough in systolic blood pressure in young healthy adults: Possible circadian effects.Physiological reports · 2026Article
- A circadian clock gene homolog regulates developmental timing and male mating circuitry iniScience · 2026Article
- Home-Court Advantage and the Associations of Travel and Jet Lag with Team Performance in the Women's National Basketball Association (WNBA).Sports medicine - open · 2026Article
- Physical activity, sleep pattern and problematic internet use in undergraduate health-sciences students of Nepal - A cross-sectional study.PLOS digital health · 2026Article
- Prenatal cell-free DNA methylome detects association with autism and maternal obesity.Communications biology · 2026Article
- Sex and age modulate the relationship between melanopsin-dependent light sensitivity and chronotype.Sleep · 2026Article
- Article
249 more citing papers are in PubMed but not listed here.
Corrections and comments
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Authors and funding
10 authors.
Funding
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.
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Registered trials
Read under generation 80e0d062 · epoch 390. Bibliography from PubMed, PubMed Central and OpenAlex; grants from NIH RePORTER; trial links from ClinicalTrials.gov; estimates, votes and beliefs from the OpenQuestion graph.