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Author |
Martin, J.S.; Laberge, L.; Sasseville, A.; Berube, M.; Alain, S.; Lavoie, J.; Houle, J.; Hebert, M. |

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Title |
Timely use of in-car dim blue light and blue blockers in the morning does not improve circadian adaptation of fast rotating shift workers |
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Journal Article |
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Year  |
2021 |
Publication |
Chronobiology International |
Abbreviated Journal |
Chronobiol Int |
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in press |
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Keywords |
Human Health; Adaptation to shift and night work; blue blocker glasses; circadian misalignment; light exposure; melatonin; sleep; sleepiness/alertness |
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Abstract |
Circadian adaptation to night work usually does not occur in naturalistic conditions, largely due to exposure to low levels of light during the night and light in the morning on the way home. This leads to circadian misalignment, which has documented deleterious effects on sleep and functioning during waking hours. Chronic circadian misalignment is also being increasingly associated with long-term health comorbidities. As the circadian system is mostly sensitive to short wavelengths (i.e., blue light) and less sensitive to long wavelengths (i.e., red light), shaping light exposure in a “wavelength-wise” manner has been proposed to promote partial adaptation to night shifts, and, therefore, alleviate circadian rhythms disruption. This report presents results from two cross-over designed studies that aimed to investigate the effects of three different light conditions on circadian phase, sleepiness, and alertness of police patrol officers on a rotating shift schedule. The first study took place during summer (n = 15) and the second study (n = 25) during winter/early spring. In both studies, all participants went through three conditions composed of four consecutive night shifts: 1) in-car dim blue light exposure during the night shift and wearing of blue-blocking glasses (BBG) in the morning after 05:00 h; 2) in-car red light exposure during the night shift and wearing of BBG in the morning after 05:00 h; 3) a control condition with no intervention. To assess circadian phase position, salivary melatonin was collected hourly the night before and the night after each condition. Sleep was monitored by wrist actigraphy. Also, a 10-min Psychomotor Vigilance-Task was administered at the beginning and end of each night shift and the Karolinska Sleepiness Scale was completed every 2 h during each night shift. In the summer study, no difference was found in alertness and sleepiness between conditions. Participants though exhibited greater ( approximately 3 h) phase delay after four consecutive night shifts in the control condition (in which morning light exposure was expected to prevent phase delay) than after the blue and red conditions ( approximately 2 h) (in which wearing BBG were expected to promote phase delay). In the second study performed during the winter/early spring, a comparable approximately 2 h phase delay was found in each of the three conditions, with no difference in alertness and sleepiness between conditions. In conclusion, participants in both studies exhibited modest phase delay across the four night shifts, even during the control conditions. Still, re-entrainment was not fast enough to produce partial circadian adaptation after four night shifts. A greater number of consecutive night shifts may be necessary to produce enough circadian alignment to elicit benefits on sleepiness and alertness in workers driving a motorized vehicle during night shifts. In-car dim blue light exposure combined with the wearing of BBG in the morning did not show the expected benefits on circadian adaptation, sleepiness, and alertness in our studies. Higher levels of light may be warranted when implementing light intervention in a motorized vehicle setting. |
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Departement d'ophtalmologie et ORL-chirurgie Cervico-faciale, Universite Laval , Quebec, Quebec, Canada |
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0742-0528 |
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PMID:33588653 |
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GFZ @ kyba @ |
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3429 |
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Hicks, D.; Attia, D.; Behar-Cohen, F.; Carre, S.; Enouf, O.; Falcon, J.; Gronfier, C.; Martinsons, C.; Metlaine, A.; Tahkamo, L.; Torriglia, A.; FrancoiseVienot |

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Title |
How good is the evidence that light at night can affect human health? |
Type |
Journal Article |
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Year  |
2020 |
Publication |
Graefe's Archive for Clinical and Experimental Ophthalmology = Albrecht von Graefes Archiv fur Klinische und Experimentelle Ophthalmologie |
Abbreviated Journal |
Graefes Arch Clin Exp Ophthalmol |
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in press |
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Commentary; artificial light at night; human health |
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Light pollution and exposure to artificial light at night (ALAN) have become almost universal in the modern world. Although there is an ongoing debate about how such environmental changes can affect human well-being and health, there is no doubt that ALAN perturbs the circadian clock – an ancestral system which synchronizes bodily physiology with the day-night cycle. The eye, especially the retina, has a dual role in this story – on the one hand, it is the unique source of light entry to the central clock in the brain, and on the other, eyes themselves are strongly regulated by endogenous circadian clocks. This editorial gives a very brief overview of the situation and poses certain unanswered questions. |
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Museum National d'Histoire Naturelle, Paris, France |
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0721-832X |
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PMID:31900646 |
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no |
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GFZ @ kyba @ |
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2791 |
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Sletten, T.L.; Cappuccio, F.P.; Davidson, A.J.; Van Cauter, E.; Rajaratnam, S.M.W.; Scheer, F.A.J.L. |

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Title |
Health consequences of circadian disruption |
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Journal Article |
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Year  |
2020 |
Publication |
Sleep |
Abbreviated Journal |
Sleep |
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43 |
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1 |
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Keywords |
Human Health; Circadian Rhythm; Chronobiology; Sleep; Review |
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The circadian system is key for optimal functioning by maintaining synchrony between internal circadian rhythms, behaviors, and external cues. Many clinicians are not fully aware, however, of the far-reaching implications of the circadian system for human health. Clinical attention to circadian rhythms has largely focused on sleep disturbances. The impact of the circadian system on health is, however, much broader. Clinical diagnoses are often based on single time point assessments during the day, ignoring circadian influences on physiology. Even when time is considered, using (external) clock time ignores the large interindividual differences in internal timing. |
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Division of Sleep Medicine, Harvard Medical School, Boston, MA |
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0161-8105 |
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PMID:31930347 |
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IDA @ john @ |
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2822 |
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Ritonja, J.; McIsaac, M.A.; Sanders, E.; Kyba, C.C.M.; Grundy, A.; Cordina-Duverger, E.; Spinelli, J.J.; Aronson, K.J. |

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Title |
Outdoor light at night at residences and breast cancer risk in Canada |
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Journal Article |
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Year  |
2020 |
Publication |
European Journal of Epidemiology |
Abbreviated Journal |
Eur J Epidemiol |
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in press |
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Human Health; Breast cancer; Case-control study; Circadian disruption; Light at night; Night work; Women's health |
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Experimental and epidemiologic studies suggest that light at night (LAN) exposure disrupts circadian rhythm, and this disruption may increase breast cancer risk. We investigated the potential association between residential outdoor LAN and breast cancer risk. A population-based case-control study was conducted in Vancouver, British Columbia and Kingston, Ontario, Canada with incident breast cancer cases, and controls frequency matched by age in the same region. This analysis was restricted to 844 cases and 905 controls who provided lifetime residential histories. Using time-weighted average duration at each home 5-20 years prior to study entry, two measures of cumulative average outdoor LAN were calculated using two satellite data sources. Logistic regression was used to estimate the relationship between outdoor LAN and breast cancer risk, considering interactions for menopausal status and night shift work. We found no association between residential outdoor LAN and breast cancer for either measure of LAN [OR comparing highest vs. lowest tertile (DNB) = 0.95, 95% CI 0.70-1.27]. We also found no association when considering interactions for menopausal status and past/current night work status. These findings were robust to changes to years of residential data considered, residential mobility, and longer exposure windows. Our findings are consistent with studies reporting that outdoor LAN has a small effect or no effect on breast cancer risk. |
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Division of Cancer Care and Epidemiology, Cancer Research Institute, Queen's University, Kingston, ON, Canada. aronson@queensu.ca |
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0393-2990 |
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PMID:32026169 |
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no |
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GFZ @ kyba @ |
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2826 |
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Author |
Letzkus, L. |
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Title |
Red Light at Night: A Feasibility Study in Hospitalized Patients |
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Journal Article |
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Year  |
2020 |
Publication |
MEDSURG Nursing |
Abbreviated Journal |
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29 |
Issue |
1 |
Pages |
38-42 |
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Keywords |
Human Health |
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Abstract |
Light can be a noxious stimulus during hospitalization. The study evaluated use of a red night-light intervention for hospitalized adults. The red light was found to be a feasible intervention and well received by participants. |
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GFZ @ kyba @ |
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2831 |
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