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Author Sasseville, A.; Benhaberou-Brun, D.; Fontaine, C.; Charon, M.-C.; Hebert, M.
Title Wearing blue-blockers in the morning could improve sleep of workers on a permanent night schedule: a pilot study Type Journal Article
Year (down) 2009 Publication Chronobiology International Abbreviated Journal Chronobiol Int
Volume 26 Issue 5 Pages 913-925
Keywords Adaptation, Physiological; Adult; Biological Clocks; Circadian Rhythm; Female; Humans; *Light; Male; Middle Aged; Photoperiod; Pilot Projects; Seasons; *Sleep; Wakefulness; *Work Schedule Tolerance; shift work; blue light; blue blocker; light therapy
Abstract Night shiftworkers often complain of disturbed sleep during the day. This could be partly caused by morning sunlight exposure during the commute home, which tends to maintain the circadian clock on a daytime rhythm. The circadian clock is most sensitive to the blue portion of the visible spectrum, so our aim was to determine if blocking short wavelengths of light below 540 nm could improve daytime sleep quality and nighttime vigilance of night shiftworkers. Eight permanent night shiftworkers (32-56 yrs of age) of Quebec City's Canada Post distribution center were evaluated during summertime, and twenty others (24-55 yrs of age) during fall and winter. Timing, efficacy, and fragmentation of daytime sleep were analyzed over four weeks by a wrist activity monitor, and subjective vigilance was additionally assessed at the end of the night shift in the fall-winter group. The first two weeks served as baseline and the remaining two as experimental weeks when workers had to wear blue-blockers glasses, either just before leaving the workplace at the end of their shift (summer group) or 2 h before the end of the night shift (fall-winter group). They all had to wear the glasses when outside during the day until 16:00 h. When wearing the glasses, workers slept, on average +/-SD, 32+/-29 and 34+/-60 more min/day, increased their sleep efficacy by 1.95+/-2.17% and 4.56+/-6.1%, and lowered their sleep fragmentation by 1.74+/-1.36% and 4.22+/-9.16% in the summer and fall-winter group, respectively. Subjective vigilance also generally improved on Fridays in the fall-winter group. Blue-blockers seem to improve daytime sleep of permanent night-shift workers.
Address Centre de Recherche Universite Laval Robert-Giffard/Department of Oto Rhino Laryngology and Ophtalmology, Universite Laval, Quebec, Canada
Corporate Author Thesis
Publisher Place of Publication Editor
Language English Summary Language Original Title
Series Editor Series Title Abbreviated Series Title
Series Volume Series Issue Edition
ISSN 0742-0528 ISBN Medium
Area Expedition Conference
Notes PMID:19637050 Approved no
Call Number IDA @ john @ Serial 295
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Author Bennett, S.; Alpert, M.; Kubulins, V.; Hansler, R.L.
Title Use of modified spectacles and light bulbs to block blue light at night may prevent postpartum depression Type Journal Article
Year (down) 2009 Publication Medical Hypotheses Abbreviated Journal Med Hypotheses
Volume 73 Issue 2 Pages 251-253
Keywords Depression, Postpartum/*prevention & control; *Eyeglasses; Female; Humans; *Lighting; blue light; light therapy; blue blocker
Abstract In 2001 it was discovered that exposing the eyes to light in the blue end of the visible spectrum suppresses the production of the sleep hormone, melatonin. New mothers need to get up during the night to care for their babies. This is the time when melatonin is normally flowing. Exposing their eyes to light can cut off the flow. It may also reset their circadian (internal) clock. On subsequent nights the melatonin may not begin flowing at the normal time making it difficult to fall asleep. Over time, disruption of the circadian rhythm plus sleep deprivation may result in depression. Women suffering postpartum depression were enrolled in a small clinical trial. Some were provided with glasses and light bulbs that block blue light. Others were equipped with glasses and light bulbs that looked colored but did not block the rays causing melatonin suppression. Those with the “real glasses” recovered somewhat more quickly than those with the placebo glasses and light bulbs. The hypothesis that should be tested in large scale clinical trials is that the risk of postpartum depression can be reduced when a new mother avoids exposing her eyes to blue light when she gets up at night to care for her baby. In the meantime, all new mothers may benefit from using glasses and light bulbs that block blue light when getting up at night to care for their babies.
Address Postpartum Support, International P.O. Box 60931, Santa Barbara, CA 93160, USA
Corporate Author Thesis
Publisher Place of Publication Editor
Language English Summary Language Original Title
Series Editor Series Title Abbreviated Series Title
Series Volume Series Issue Edition
ISSN 0306-9877 ISBN Medium
Area Expedition Conference
Notes PMID:19329259 Approved no
Call Number IDA @ john @ Serial 296
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Author Thorne, H.C.; Jones, K.H.; Peters, S.P.; Archer, S.N.; Dijk, D.-J.
Title Daily and seasonal variation in the spectral composition of light exposure in humans Type Journal Article
Year (down) 2009 Publication Chronobiology International Abbreviated Journal Chronobiol Int
Volume 26 Issue 5 Pages 854-866
Keywords Adolescent; Adult; Circadian Rhythm; Climate; Female; Genetic Variation; Humans; *Light; Male; Photochemistry/methods; Research Design; Rod Opsins/chemistry/genetics; *Seasons; Sleep
Abstract Light is considered the most potent synchronizer of the human circadian system and exerts many other non-image-forming effects, including those that affect brain function. These effects are mediated in part by intrinsically photosensitive retinal ganglion cells that express the photopigment melanopsin. The spectral sensitivity of melanopsin is greatest for blue light at approximately 480 nm. At present, there is little information on how the spectral composition of light to which people are exposed varies over the 24 h period and across seasons. Twenty-two subjects, aged 22+/-4 yrs (mean+/-SD) participated during the winter months (November-February), and 12 subjects aged 25+/-3 yrs participated during the summer months (April-August). Subjects wore Actiwatch-RGB monitors, as well as Actiwatch-L monitors, for seven consecutive days while living in England. These monitors measured activity and light exposure in the red, green, and blue spectral regions, in addition to broad-spectrum white light, with a 2 min resolution. Light exposure during the day was analyzed for the interval between 09:00 and 21:00 h. The time course of white-light exposure differed significantly between seasons (p = 0.0022), with light exposure increasing in the morning hours and declining in the afternoon hours, and with a more prominent decline in the winter. Overall light exposure was significantly higher in summer than winter (p = 0.0002). Seasonal differences in the relative contribution of blue-light exposure to overall light exposure were also observed (p = 0.0006), in particular during the evening hours. During the summer evenings (17:00-21:00 h), the relative contribution of blue light was significantly higher (p < 0.0001) (40.2+/-1.1%) than during winter evenings (26.6+/-0.9%). The present data show that in addition to overall light exposure, the spectral composition of light exposure varies over the day and with season.
Address Surrey Sleep Research Centre, Faculty of Health and Medical Sciences, University of Surrey, Guildford, Surrey, UK. helen.thorne@surrey.ac.uk
Corporate Author Thesis
Publisher Place of Publication Editor
Language English Summary Language Original Title
Series Editor Series Title Abbreviated Series Title
Series Volume Series Issue Edition
ISSN 0742-0528 ISBN Medium
Area Expedition Conference
Notes PMID:19637047 Approved no
Call Number IDA @ john @ Serial 298
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Author Stevens, R.G.
Title Light-at-night, circadian disruption and breast cancer: assessment of existing evidence Type Journal Article
Year (down) 2009 Publication International Journal of Epidemiology Abbreviated Journal Int J Epidemiol
Volume 38 Issue 4 Pages 963-970
Keywords Human Health; Animals; Blindness/complications/epidemiology; Breast Neoplasms/epidemiology/*etiology/metabolism; Chronobiology Disorders/*complications/epidemiology/metabolism; Circadian Rhythm/physiology; Disease Models, Animal; Female; Humans; Light Signal Transduction/physiology; Lighting/adverse effects; Melatonin/biosynthesis; Sleep/physiology; Time Factors; *Work Schedule Tolerance
Abstract BACKGROUND: Breast cancer incidence is increasing globally for largely unknown reasons. The possibility that a portion of the breast cancer burden might be explained by the introduction and increasing use of electricity to light the night was suggested >20 years ago. METHODS: The theory is based on nocturnal light-induced disruption of circadian rhythms, notably reduction of melatonin synthesis. It has formed the basis for a series of predictions including that non-day shift work would increase risk, blind women would be at lower risk, long sleep duration would lower risk and community nighttime light level would co-distribute with breast cancer incidence on the population level. RESULTS: Accumulation of epidemiological evidence has accelerated in recent years, reflected in an International Agency for Research on Cancer (IARC) classification of shift work as a probable human carcinogen (2A). There is also a strong rodent model in support of the light-at-night (LAN) idea. CONCLUSION: If a consensus eventually emerges that LAN does increase risk, then the mechanisms for the effect are important to elucidate for intervention and mitigation. The basic understanding of phototransduction for the circadian system, and of the molecular genetics of circadian rhythm generation are both advancing rapidly, and will provide for the development of lighting technologies at home and at work that minimize circadian disruption, while maintaining visual efficiency and aesthetics. In the interim, there are strategies now available to reduce the potential for circadian disruption, which include extending the daily dark period, appreciate nocturnal awakening in the dark, using dim red light for nighttime necessities, and unless recommended by a physician, not taking melatonin tablets.
Address Department of Community Medicine, University of Connecticut Health Center, 263 Farmington Avenue, Farmington, CT 06030-6325, USA. bugs@uchc.edu
Corporate Author Thesis
Publisher Place of Publication Editor
Language English Summary Language Original Title
Series Editor Series Title Abbreviated Series Title
Series Volume Series Issue Edition
ISSN 0300-5771 ISBN Medium
Area Expedition Conference
Notes PMID:19380369; PMCID:PMC2734067 Approved no
Call Number LoNNe @ christopher.kyba @ Serial 527
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Author Kloog, I.; Haim, A.; Stevens, R.G.; Barchana, M.; Portnov, B.A.
Title Light at night co-distributes with incident breast but not lung cancer in the female population of Israel Type Journal Article
Year (down) 2008 Publication Chronobiology International Abbreviated Journal Chronobiol Int
Volume 25 Issue 1 Pages 65-81
Keywords Human Health; Breast Neoplasms/*epidemiology/etiology; Female; Humans; Israel/epidemiology; *Light; Lung Neoplasms/epidemiology; Multivariate Analysis; Risk Factors
Abstract Recent studies of shift-working women have reported that excessive exposure to light at night (LAN) may be a risk factor for breast cancer. However, no studies have yet attempted to examine the co-distribution of LAN and breast cancer incidence on a population level with the goal to assess the coherence of these earlier findings with population trends. Coherence is one of Hill's “criteria” (actually, viewpoints) for an inference of causality. Nighttime satellite images were used to estimate LAN levels in 147 communities in Israel. Multiple regression analysis was performed to investigate the association between LAN and breast cancer incidence rates and, as a test of the specificity of our method, lung cancer incidence rates in women across localities under the prediction of a link with breast cancer but not lung cancer. After adjusting for several variables available on a population level, such as ethnic makeup, birth rate, population density, and local income level, a strong positive association between LAN intensity and breast cancer rate was revealed (p<0.05), and this association strengthened (p<0.01) when only statistically significant factors were filtered out by stepwise regression analysis. Concurrently, no association was found between LAN intensity and lung cancer rate. These results provide coherence of the previously reported case-control and cohort studies with the co-distribution of LAN and breast cancer on a population basis. The analysis yielded an estimated 73% higher breast cancer incidence in the highest LAN exposed communities compared to the lowest LAN exposed communities.
Address Department of Natural Resources & Environmental Management, University of Haifa, Haifa, Israel
Corporate Author Thesis
Publisher Place of Publication Editor
Language English Summary Language Original Title
Series Editor Series Title Abbreviated Series Title
Series Volume Series Issue Edition
ISSN 0742-0528 ISBN Medium
Area Expedition Conference
Notes PMID:18293150 Approved no
Call Number LoNNe @ christopher.kyba @ Serial 528
Permanent link to this record