| Records |
| Author |
Dumont, M.; Beaulieu, C. |
| Title |
Light exposure in the natural environment: relevance to mood and sleep disorders |
Type |
Journal Article |
Year  |
2007 |
Publication |
Sleep Medicine |
Abbreviated Journal |
Sleep Med |
| Volume |
8 |
Issue |
6 |
Pages |
557-565 |
| Keywords |
Human Health; Affect; *Biological Clocks; *Circadian Rhythm; Humans; *Light; Mood Disorders/*etiology; Sleep Disorders, Circadian Rhythm/*complications; Wakefulness; Work Schedule Tolerance |
| Abstract |
In addition to being necessary for vision, light also plays a primary role in circadian physiology. Humans are diurnal animals and their biological clock synchronizes their physiological functions in such a way that functions associated with activity happen in the daytime while functions associated with rest occur at night. A misalignment between the endogenous circadian clock and the desired sleep schedule is the main cause of circadian sleep disorders; it may be involved in certain mood disorders as well. Since light is the main environmental cue used by the biological clock to set its own timing in relation to the day-night cycle, inappropriate light exposure can be involved in the physiopathology of circadian disorders. Conversely, when handled properly, controlled light exposure can be used to treat some mood and sleep disorders. While the earliest studies in the field focused solely on exposure to bright light, contemporary studies aim at understanding how the entire profile of light-dark exposure can influence the circadian clock and, consequently, mood, sleep, and vigilance quality. Following a brief summary of the main concepts underlying the non-visual effects of light, this paper presents some studies using ambulatory measurements of light exposure to illustrate how these concepts apply in real-life situations and discusses the clinical relevance of light exposure in the natural environment for mood, sleep, and circadian disorders. |
| Address |
Chronobiology Laboratory, Sacre-Coeur Hospital of Montreal, Montreal, Quebec, Canada H4J 1C5. marie.dumont@umontreal.ca |
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| Language |
English |
Summary Language |
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Series Title |
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| ISSN |
1389-9457 |
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| Notes |
PMID:17383230 |
Approved |
no |
| Call Number |
LoNNe @ kagoburian @ |
Serial |
736 |
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| Author |
Skene, D.J.; Arendt, J. |
| Title |
Circadian rhythm sleep disorders in the blind and their treatment with melatonin |
Type |
Journal Article |
| Year |
2007 |
Publication |
Sleep Medicine |
Abbreviated Journal |
Sleep Med |
| Volume |
8 |
Issue |
6 |
Pages |
651-655 |
| Keywords |
Human Health; Blindness/*complications; Chronotherapy; Circadian Rhythm/drug effects; Humans; Melatonin/*administration & dosage; Sleep/drug effects; Sleep Disorders, Circadian Rhythm/*drug therapy/*etiology; Treatment Outcome |
| Abstract |
People who are blind, in addition to having to cope with partial or no sight, have an added handicap; the transmission of ocular light from the retina to their circadian clock is impaired. At its worse, for example in people with both eyes enucleated, this lesion results in desynchronisation of the biological clock (located in the hypothalamic suprachiasmatic nuclei) from the 24h day/night environment. While in a desynchronised state, symptoms akin to jet lag are experienced (e.g., daytime sleepiness, poor night sleep, reduced alertness and performance during waking). This is a lifelong condition. Daily administration of exogenous melatonin is the current treatment of choice for this so-called “non-24h sleep/wake disorder”. Melatonin has been shown to correct the underlying circadian rhythm abnormality as well as improve sleep and reduce daytime napping. The effectiveness of melatonin therapy depends upon its time of administration relative to the timing of the person's circadian clock. If practicable, assessment of an individual's circadian phase (by measurement of the endogenous melatonin rhythm in plasma, saliva or urine) is recommended prior to commencing treatment to optimise melatonin's effectiveness. |
| Address |
Centre for Chronobiology, School of Biomedical and Molecular Sciences, University of Surrey, Guildford GU2 7XH, UK. d.skene@surrey.ac.uk |
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English |
Summary Language |
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Original Title |
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Series Title |
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Abbreviated Series Title |
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Edition |
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| ISSN |
1389-9457 |
ISBN |
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Medium |
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Expedition |
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Conference |
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| Notes |
PMID:17420154 |
Approved |
no |
| Call Number |
LoNNe @ kagoburian @ |
Serial |
811 |
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| Author |
Middleton, B.; Arendt, J.; Stone, BM |
| Title |
Human circadian rhythms in constant dim light (8 lux) with knowledge of clock time |
Type |
Journal Article |
| Year |
1996 |
Publication |
Journal of Sleep Research |
Abbreviated Journal |
J. Sleep Res. |
| Volume |
5 |
Issue |
2 |
Pages |
69-76 |
| Keywords |
Human Health; circadian rhythm; light/dark cycle; melatonin; entrainment; melatonin levels; 6-sulphatoxymelatonin |
| Abstract |
The light/dark (L/D) cycle is a major synchronizer of human circadian rhythms. In the absence of a strong L/D cycle, synchrony with 24 hours can nevertheless be maintained in a socially structured environment, as shown in Polar regions (Broadway et al. 1987) and by some blind subjects (Czeisler et al. 1995a). The relative contribution of other time cues to entrainment in dim light has not been fully explored. The present study investigated the behaviour of melatonin (assessed as 6-sulphatoxymelatonin); rectal temperature; activity and sleep (actigraphy and logs) in constant dim light (L/ L) with access to a digital clock. 6 normal healthy males were maintained as a group in partial temporal isolation with attenuated sound and ambient temperature for 21 days. All 6 subjects showed free-running periodicity for 6-sulphatoxymelatonin and 5/6 subjects for temperature, activity and sleep offset. The average period (tau) was 24.26 +/- 0.049, substantially shorter than in previous experiments with a self selected L/D cycle but similar to a recent study conducted in very dim light. One subject maintained a rigid sleep/wake cycle throughout whilst his 6-sulphatoxymelatonin rhythm free-ran. Total sleep time, from actigraph data, did not change but sleep efficiency decreased during the experiment. The subjects did not show group synchronization. These results confirm previous data indicating the importance of the L/D cycle in human entrainment and underline the lesser role of social cues and knowledge of clock time. This particular approach will permit the administration of timed medication to sighted humans under free-running conditions. |
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Wiley |
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IDA @ john @ |
Serial |
1098 |
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