Free-running sleep

Free-running sleep is a sleep pattern characterised by sleep times not entrained to normal time cues; often referring to a later shifting (delay) on a daily basis. This occurs as the circadian rhythm sleep disorder non-24-hour sleep–wake disorder,[1] or when artificially induced in experiments studying circadian rhythms and other biological rhythms within the field of chronobiology.

Background

An individual's or organism's circadian phase can be determined by monitoring an output of the circadian system, the internal circadian clock. A researcher can precisely determine factors such as daily cycles of genetic activity, body temperature, blood pressure, hormone secretion, or sleep and activity/alertness patterns. Alertness can be tracked in humans through performance-based tests or other measures (such as somnolence),[2][3] whereas in animals it can be assessed by observing trends in physical activity (for example, wheel-running in rodents).

In research settings

When humans or organisms free-run, experiments can be conducted to determine which signals, known as zeitgebers, are effective in entrainment.[4] Study subjects are shielded from all time cues, often following protocols such as continuous light, continuous dark, or combined light/dark alternations to which the organism is unable to entrain; for example, a very short (or ultradian) period of one hour dark and two hours light.[3][5] Other rhythm disruptions may be used, such as providing limited amounts at short intervals to avoid entrainment to average mealtimes. These modifications can show the strength and influence of the intrinsic circadian clock.

Researchers can conduct studies to measure entrainment for various organisms and the bounds of circadian cycle lengths. For example, some animals can be entrained to a 22-hour day, but not to a 20-hour day.[4] Although previous consensus showed human cycles averaging as short as 23.5 hours, or as long as 24.65 hours, several more recent studies determined a tighter average range around 24.18 hours.[4] Observations of free-running and circadian rhythm flexibility are also applicable to situations such as sleep during space travel, for example, for reduced day lengths required of astronauts over short periods, or when considering the length of day on a planet such as Mars (24.65 hours).[2][4]

Masking refers to the effects of non-circadian factors within experiments which could obscure existing patterns or create the appearance of a non-existent rhythm, impacting measurement of timings.[3] Some examples of masking factors include background noise, ambient temperature, distractions, lighting conditions, or boredom during the study.[3]

In humans

Main article: Non-24-hour sleep–wake disorder

Non-24-hour sleep–wake disorder (Non-24 or N24), formerly referred to free-running disorder (FRD), is a circadian rhythm sleep disorder.[6] The difference between circadian length and the 24-hour day, while inadequately synchronised by zeitgebers, results in free running.[7] Non-24 affects more than half of people who are totally blind[8] and a small number of sighted individuals.[9]

Among blind people, the cause is the inability to adequately register light cues, preventing entrainment.[6] Many blind people who are able to entrain to a 24-hour light/dark cycle retain functioning retinae, including operative non-visual light-sensitive cells called ipRGCs.[10] These ganglion cells, which contain melanopsin, relay signals to the circadian clock via the retinohypothalamic tract (branching off from the optic nerve), which is the pathway from the retina to the pineal gland.[11][12]

Among sighted individuals, non-24 usually first appears during the teens or early twenties. As with delayed sleep phase disorder (DSPS or DSPD), in the absence of neurological damage due to trauma or stroke, cases rarely develop after age 30.[9] In a case review, non-24 affected more sighted men than sighted women.[9] A quarter of sighted subjects with non-24 also have an associated psychiatric condition.[9] A quarter previously showed symptoms of DSPS.[9]

See also

References

  1. ^ "Circadian Rhythm Sleep Disorders" (PDF). aasm. Archived (PDF) from the original on 11 June 2016. Retrieved 4 July 2024.
  2. ^ a b Basner, Mathias; Dinges, David F.; Mollicone, Daniel; Ecker, Adrian; Jones, Christopher W.; Hyder, Eric C.; Di Antonio, Adrian; Savelev, Igor; Kan, Kevin; Goel, Namni; Morukov, Boris V.; Sutton, Jeffrey P. (2013-02-12). "Mars 520-d mission simulation reveals protracted crew hypokinesis and alterations of sleep duration and timing". Proceedings of the National Academy of Sciences. 110 (7): 2635–2640. doi:10.1073/pnas.1212646110. ISSN 0027-8424. PMC 3574912. PMID 23297197.
  3. ^ a b c d Van Dongen, Hans PA; Dinges, David F. (2000). "Circadian rhythms in fatigue, alertness, and performance" (PDF). Principles and practice of sleep medicine. 20. W. B. Saunders: 391–399. Archived (PDF) from the original on 2025-10-11. Retrieved 2026-03-15.
  4. ^ a b c d Scheer, Frank A.J.L.; Kenneth P. Wright Jr.; Richard E. Kronauer; Charles A. Czeisler (2007-08-08). Nicolelis, Miguel (ed.). "Plasticity of the Intrinsic Period of the Human Circadian Timing System". PLOS ONE. 2 (1): e721. Bibcode:2007PLoSO...2..721S. doi:10.1371/journal.pone.0000721. PMC 1934931. PMID 17684566. [E]xposure to moderately bright light (~450 lux; ~1.2 W/m2) for the second or first half of the scheduled wake episode is effective for entraining individuals to the 24.65-h Martian sol and a 23.5-h day length, respectively.
  5. ^ Burgess, Helen J.; Eastman, Charmane I. (2008-08-01). "Human Tau in an Ultradian Light-Dark Cycle". Journal of Biological Rhythms. 23 (4). Sage Publishing: 374–376. doi:10.1177/0748730408318592. PMC 3622149. PMID 18663244.
  6. ^ a b Pacheco, Danielle (2018-10-13). "Non-24-Hour Sleep Wake Disorder". Sleep Foundation. Retrieved 2026-03-15.
  7. ^ Quera Salva, Maria Antonia; Hartley, Sarah; Léger, Damien; Dauvilliers, Yves A. (2017-12-18). "Non-24-Hour Sleep–Wake Rhythm Disorder in the Totally Blind: Diagnosis and Management". Frontiers in Neurology. 8: 686. doi:10.3389/fneur.2017.00686. ISSN 1664-2295. PMC 5741691. PMID 29326647.
  8. ^ Teofilo Lee-Chiong (2006). Sleep: a comprehensive handbook. New York: Wiley-Liss. p. 385. ISBN 0-471-68371-X.
  9. ^ a b c d e Sack, Robert L.; Auckley, Dennis; Auger, R. Robert; Carskadon, Mary A.; Wright, Kenneth P.; Vitiello, Michael V.; Zhdanova, Irina V. (2007-11-01). "Circadian Rhythm Sleep Disorders: Part II, Advanced Sleep Phase Disorder, Delayed Sleep Phase Disorder, Free-Running Disorder, and Irregular Sleep-Wake Rhythm". Sleep. 30 (11): 1484–1501. doi:10.1093/sleep/30.11.1484. ISSN 1550-9109. PMC 2082099. PMID 18041481.
  10. ^ Tu, Daniel C.; Zhang, Dongyang; Demas, Jay; Slutsky, Elon B.; et al. (December 2005). "Physiologic diversity and development of intrinsically photosensitive retinal ganglion cells". Neuron. 48 (6): 987–99. doi:10.1016/j.neuron.2005.09.031. PMID 16364902. Intrinsically photosensitive retinal ganglion cells (ipRGCs) mediate numerous nonvisual phenomena, including entrainment of the circadian clock to light-dark cycles, pupillary light responsiveness, and light-regulated hormone release.
  11. ^ Czeisler, Charles A.; Theresa L. Shanahan; Elizabeth B. Klerman; Heinz Martens; Daniel J. Brotman; Jonathan S. Emens; Torsten Klein; Joseph F. Rizzo (5 January 1995). "Suppression of melatonin secretion in some blind patients by exposure to bright light". N Engl J Med. 332 (1). USA: 6–11. doi:10.1056/NEJM199501053320102. PMID 7990870. [T]he photic pathway used by the circadian system is functionally intact in some blind patients.
  12. ^ Arendt, Josephine (2006-02-01). "Chapter 15. The Pineal Gland and Pineal Tumours". Neuroendocrinology, Hypothalamus, and Pituitary. Endotext.com. pp. an E–book edited by Ashley Grossman (chapter section: Melatonin Synthesis and Metabolism). Archived from the original on 2008-02-09. Retrieved 2008-02-07. Image forming vision (rods and cones) is not required ... for synchronising/phase shifting the circadian clock.
This article is issued from Wikipedia. The text is available under Creative Commons Attribution-Share Alike 4.0 unless otherwise noted. Additional terms may apply for the media files.