| Records |
| Author |
Arendt, J. |
| Title |
Biological rhythms during residence in polar regions |
Type |
Journal Article |
| Year |
2012 |
Publication |
Chronobiology International |
Abbreviated Journal |
Chronobiol Int |
| Volume |
29 |
Issue |
4 |
Pages |
379-394 |
| Keywords |
*Acclimatization; Activities of Daily Living; Affect; Antarctic Regions; Arctic Regions; *Biological Clocks; *Circadian Rhythm; *Cold Climate; *Cold Temperature; Energy Metabolism; Feeding Behavior; Humans; Melatonin/metabolism; Personnel Staffing and Scheduling; *Photoperiod; Seasonal Affective Disorder/physiopathology/prevention & control/psychology; *Seasons; Sleep; Sleep Disorders, Circadian Rhythm/etiology/physiopathology/*prevention & control/psychology; Time Factors; Workload; Workplace |
| Abstract |
At Arctic and Antarctic latitudes, personnel are deprived of natural sunlight in winter and have continuous daylight in summer: light of sufficient intensity and suitable spectral composition is the main factor that maintains the 24-h period of human circadian rhythms. Thus, the status of the circadian system is of interest. Moreover, the relatively controlled artificial light conditions in winter are conducive to experimentation with different types of light treatment. The hormone melatonin and/or its metabolite 6-sulfatoxymelatonin (aMT6s) provide probably the best index of circadian (and seasonal) timing. A frequent observation has been a delay of the circadian system in winter. A skeleton photoperiod (2 x 1-h, bright white light, morning and evening) can restore summer timing. A single 1-h pulse of light in the morning may be sufficient. A few people desynchronize from the 24-h day (free-run) and show their intrinsic circadian period, usually >24 h. With regard to general health in polar regions, intermittent reports describe abnormalities in various physiological processes from the point of view of daily and seasonal rhythms, but positive health outcomes are also published. True winter depression (SAD) appears to be rare, although subsyndromal SAD is reported. Probably of most concern are the numerous reports of sleep problems. These have prompted investigations of the underlying mechanisms and treatment interventions. A delay of the circadian system with “normal” working hours implies sleep is attempted at a suboptimal phase. Decrements in sleep efficiency, latency, duration, and quality are also seen in winter. Increasing the intensity of ambient light exposure throughout the day advanced circadian phase and was associated with benefits for sleep: blue-enriched light was slightly more effective than standard white light. Effects on performance remain to be fully investigated. At 75 degrees S, base personnel adapt the circadian system to night work within a week, in contrast to temperate zones where complete adaptation rarely occurs. A similar situation occurs on high-latitude North Sea oil installations, especially when working 18:00-06:00 h. Lack of conflicting light exposure (and “social obligations”) is the probable explanation. Many have problems returning to day work, showing circadian desynchrony. Timed light treatment again has helped to restore normal phase/sleep in a small number of people. Postprandial response to meals is compromised during periods of desynchrony with evidence of insulin resistance and elevated triglycerides, risk factors for heart disease. Only small numbers of subjects have been studied intensively in polar regions; however, these observations suggest that suboptimal light conditions are deleterious to health. They apply equally to people living in temperate zones with insufficient light exposure. |
| Address |
Centre for Chronobiology, Faculty of Health and Medical Sciences, University of Surrey, Guildford, Surrey, UK. arendtjo@gmail.com |
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English |
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0742-0528 |
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| Notes |
PMID:22497433; PMCID:PMC3793275 |
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no |
| Call Number |
IDA @ john @ |
Serial |
143 |
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| Author |
Boivin, D.B.; Boudreau, P.; James, F.O.; Kin, N.M.K.N.Y. |
| Title |
Photic resetting in night-shift work: impact on nurses' sleep |
Type |
Journal Article |
| Year |
2012 |
Publication |
Chronobiology International |
Abbreviated Journal |
Chronobiol Int |
| Volume |
29 |
Issue |
5 |
Pages |
619-628 |
| Keywords |
Adaptation, Physiological; Adult; *Circadian Rhythm; *Darkness; Female; Humans; *Light; Male; Melatonin/metabolism; Middle Aged; *Nurses; Sleep/*physiology; Work Schedule Tolerance/*physiology |
| Abstract |
The objective of this study was to quantify daytime sleep in night-shift workers with and without an intervention designed to recover the normal relationship between the endogenous circadian pacemaker and the sleep/wake cycle. Workers of the treatment group received intermittent exposure to full-spectrum bright light during night shifts and wore dark goggles during the morning commute home. All workers maintained stable 8-h daytime sleep/darkness schedules. The authors found that workers of the treatment group had daytime sleep episodes that lasted 7.1 +/- .1 h (mean +/- SEM) versus 6.6 +/- .2 h for workers in the control group (p = .04). The increase in total sleep time co-occurred with a larger proportion of the melatonin secretory episode during daytime sleep in workers of the treatment group. The results of this study showed reestablishment of a phase angle that is comparable to that observed on a day-oriented schedule favors longer daytime sleep episodes in night-shift workers. (Author correspondence: diane.boivin@douglas.mcgill.ca ). |
| Address |
Centre for Study and Treatment of Circadian Rhythms, Douglas Mental Health University Institute, Department of Psychiatry, McGill University, Montreal, Quebec, Canada. diane.boivin@douglas.mcgill.ca |
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0742-0528 |
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| Notes |
PMID:22621359 |
Approved |
no |
| Call Number |
IDA @ john @ |
Serial |
144 |
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| Author |
Chang, A.-M.; Scheer, F.A.J.L.; Czeisler, C.A.; Aeschbach, D. |
| Title |
Direct effects of light on alertness, vigilance, and the waking electroencephalogram in humans depend on prior light history |
Type |
Journal Article |
| Year |
2013 |
Publication |
Sleep |
Abbreviated Journal |
Sleep |
| Volume |
36 |
Issue |
8 |
Pages |
1239-1246 |
| Keywords |
Arousal/*radiation effects; Attention/radiation effects; Cross-Over Studies; *Electroencephalography; Female; Humans; *Light; Male; Melatonin/blood/physiology; Psychomotor Performance/radiation effects; Reaction Time; Wakefulness/*radiation effects; Young Adult; Light history; alertness and performance; light exposure |
| Abstract |
STUDY OBJECTIVES: Light can induce an acute alerting response in humans; however, it is unknown whether the magnitude of this response is simply a function of the absolute illuminance of the light itself, or whether it depends on illuminance history preceding the stimulus. Here, we compared the effects of illuminance history on the alerting response to a subsequent light stimulus. DESIGN: A randomized, crossover design was used to compare the effect of two illuminance histories (1 lux vs. 90 lux) on the alerting response to a 6.5-h 90-lux light stimulus during the biological night. SETTING: Intensive Physiologic Monitoring Unit, Brigham and Women's Hospital, Boston, MA. PARTICIPANTS: Fourteen healthy young adults (6 F; 23.5 +/- 2.9 years). INTERVENTIONS: Participants were administered two 6.5-h light exposures (LE) of 90 lux during the biological night. For 3 days prior to each LE, participants were exposed to either 1 lux or 90 lux during the wake episode. MEASUREMENTS AND RESULTS: The alerting response to light was assessed using subjective sleepiness ratings, lapses of attention, and reaction times as measured with an auditory psychomotor vigilance task, as well as power density in the delta/theta range of the waking EEG. The alerting response to light was greater and lasted longer when the LE followed exposure to 1 lux compared to 90 lux light. CONCLUSION: The magnitude and duration of the alerting effect of light at night depends on the illuminance history and appears to be subject to sensitization and adaptation. |
| Address |
Division of Sleep Medicine, Brigham and Women's Hospital, Boston, MA 02115, USA. amchang@rics.bwh.harvard.edu |
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English |
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0161-8105 |
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PMID:23904684; PMCID:PMC3700721 |
Approved |
no |
| Call Number |
IDA @ john @ |
Serial |
145 |
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| Author |
Karatsoreos, I.N. |
| Title |
Effects of circadian disruption on mental and physical health |
Type |
Journal Article |
| Year |
2012 |
Publication |
Current Neurology and Neuroscience Reports |
Abbreviated Journal |
Curr Neurol Neurosci Rep |
| Volume |
12 |
Issue |
2 |
Pages |
218-225 |
| Keywords |
Chronobiology Disorders/*complications/genetics; Circadian Clocks/genetics; Cognition Disorders/*etiology/genetics; Humans; Metabolic Diseases/*etiology/genetics; Obesity/*etiology/genetics |
| Abstract |
Circadian (daily) rhythms in physiology and behavior are phylogenetically ancient and are present in almost all plants and animals. In mammals, these rhythms are generated by a master circadian clock in the suprachiasmatic nucleus of the hypothalamus, which in turn synchronizes “peripheral oscillators” throughout the brain and body in almost all cell types and organ systems. Although circadian rhythms are phylogenetically ancient, modern industrialized society and the ubiquity of electric lighting has resulted in a fundamental alteration in the relationship between an individual's endogenous circadian rhythmicity and the external environment. The ramifications of this desynchronization for mental and physical health are not fully understood, although numerous lines of evidence are emerging that link defects in circadian timing with negative health outcomes. This article explores the function of the circadian system, the effects of disrupted clocks on the brain and body, and how these effects impact mental and physical health. |
| Address |
Department of Veterinary and Comparative Anatomy, Pharmacology, and Physiology, Washington State University, 205 Wegner Hall, Pullman, WA 99164, USA. iliak@vetmed.wsu.edu |
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English |
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Edition |
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1528-4042 |
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| Notes |
PMID:22322663 |
Approved |
no |
| Call Number |
IDA @ john @ |
Serial |
146 |
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| Author |
Kretschmer, V.; Schmidt, K.-H.; Griefahn, B. |
| Title |
Bright light effects on working memory, sustained attention and concentration of elderly night shift workers |
Type |
Journal Article |
| Year |
2012 |
Publication |
Lighting Research and Technology |
Abbreviated Journal |
Lighting Research and Technology |
| Volume |
44 |
Issue |
3 |
Pages |
316-333 |
| Keywords |
shift work; light at night; light exposure; memory; concentration; human health |
| Abstract |
Night shift workers show a decline in performance during working time. Due to demographic change, the labour market requires more elderly people to work at night. Ageing is accompanied by a decrease in cognitive abilities, in the capabilities of the visual system and in coping with night work from the age of 40 onwards. This investigation focuses on the effects of bright light exposure on the working memory, concentration and sustained attention of elderly persons during three consecutive night shifts. After statistical control for neuroticism and intelligence as covariates, the results demonstrate that exposure to bright light at night reduces error rates for a working memory task and a concentration performance task but performance on a sustained attention task is completely unaffected. |
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1477-1535 |
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no |
| Call Number |
IDA @ john @ |
Serial |
147 |
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