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Author |
Kozaki, T.; Hidaka, Y.; Takakura, J.-Y.; Kusano, Y. |

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Title |
Salivary melatonin suppression under 100-Hz flickering blue light and non-flickering blue light conditions |
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Journal Article |
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Year |
2020 |
Publication |
Neuroscience Letters |
Abbreviated Journal |
Neurosci Lett |
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Volume |
722 |
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Pages  |
134857 |
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Keywords |
Human Health; Flickering light; Intrinsically photosensitive retinal ganglion cell; Light; Light emitting diode; Melatonin |
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Abstract |
Bright light at night has been known to suppress melatonin secretion. Photoreceptors, known as intrinsically photosensitive retinal ganglion cells (ipRGCs), project dark/bright information into the superchiasmatic nucleus, which regulates the circadian system. Electroretinograms of ipRGCs show fluctuation that is synchronized with light ON-OFF stimulation. This finding suggests that the flickering condition of light may have an impact on our circadian system. In this study, we evaluate light-induced melatonin suppression under flickering and non-flickering light conditions. Fifteen male subjects between the ages of 20 and 23 years (mean +/- SD, 21.9 +/- 1.9) were exposed to three light conditions (dim, 100-Hz flickering and non-flickering light) from 1:00 a.m. to 2:30 a.m. Saliva samples were taken just before 1:00 and at 1:15, 1:30, 2:00, and 2:30 a.m. Repeated-measure t-test with Bonferroni correction showed a significant decrease in melatonin levels under both 100-Hz and non-flickering light conditions compared to dim light conditions after 2:00 a.m. Moreover, at 2:30 a.m., the rate of change in melatonin level under 100 Hz of flickering light was significantly lower than that under non-flickering light. Our present findings suggest that 100-Hz flickering light may suppress melatonin secretion more than non-flickering light. |
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Department of Health and Nutrition Sciences, Nishikyushu University, 4490-9 Osaki, Kanzaki, Japan |
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0304-3940 |
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PMID:32097701 |
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GFZ @ kyba @ |
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2855 |
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Russart, K.L.G.; Chbeir, S.A.; Nelson, R.J.; Magalang, U.J. |

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Title |
Light at night exacerbates metabolic dysfunction in a polygenic mouse model of type 2 diabetes mellitus |
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Journal Article |
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Year |
2019 |
Publication |
Life Sciences |
Abbreviated Journal |
Life Sci |
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231 |
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116574 |
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Keywords |
Animals; diabetes; human health; mouse models; Type 2 diabetes; Insulin Resistance |
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AIMS: Electric lighting is beneficial to modern society; however, it is becoming apparent that light at night (LAN) is not without biological consequences. Several studies have reported negative effects of LAN on health and behavior in humans and nonhuman animals. Exposure of non-diabetic mice to dim LAN impairs glucose tolerance, whereas a return to dark nights (LD) reverses this impairment. We predicted that exposure to LAN would exacerbate the metabolic abnormalities in TALLYHO/JngJ (TH) mice, a polygenic model of type 2 diabetes mellitus (T2DM). MATERIALS AND METHODS: We exposed 7-week old male TH mice to either LD or LAN for 8-10weeks in two separate experiments. After 8weeks of light treatment, we conducted intraperitoneal glucose tolerance testing (ipGTT) followed by intraperitoneal insulin tolerance testing (ipITT). In Experiment 1, all mice were returned to LD for 4weeks, and ipITT was repeated. KEY FINDINGS: The major results of this study are i) LAN exposure for 8weeks exacerbates glucose intolerance and insulin resistance ii) the effects of LAN on insulin resistance are reversed upon return to LD, iii) LAN exposure results in a greater increase in body weight compared to LD exposure, iv) LAN increases the incidence of mice developing overt T2DM, and v) LAN exposure decreases survival of mice with T2DM. SIGNIFICANCE: In conclusion, LAN exacerbated metabolic abnormalities in a polygenic mouse model of T2DM, and these effects were reversed upon return to dark nights. The applicability of these findings to humans with T2DM needs to be determined. |
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Department of Neuroscience, The Ohio State University Wexner Medical Center, Columbus, OH 43210, USA; Department of Internal Medicine, The Ohio State University Wexner Medical Center, Columbus, OH 43210, USA |
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0024-3205 |
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PMID:31207311 |
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GFZ @ kyba @ |
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2549 |
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Author |
Xiao, H.; Cai, H.; Li, X. |

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Title |
Non-visual effects of indoor light environment on humans: A review |
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Journal Article |
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2020 |
Publication |
Physiology & Behavior |
Abbreviated Journal |
Physiology & Behavior |
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in press |
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113195 |
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Review; Human Health |
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As a result of the desire to improve living standards, increasing attention is paid to creating a comfortable and healthy lighting environment that contributes to human health and well-being. It is crucial to understand the effects of environmental lighting regulation on humans’ physical responses and mental activities. In this review, we focus on the scientific research on light-induced non-visual effects on humans, providing a systematic review of how the quantity of light, spectral changes, time of day, and duration have effects on the circadian rhythm, alertness, and mood based on eligible literature. The key findings are as follows: (1) The increase of illuminance and correlated colour temperature (CCT) at night were both positively associated with melatonin suppression, thus affecting the circadian rhythm. Meanwhile, a high CCT is conducive to the stimulation of positive mood. (2) Blue light and high CCT light at night induced delayed phase shift, and the objective alertness was reduced under the condition of lack of blue components. (3) High illuminance was positively correlated with subjective alertness during daytime, and increased the positive mood in the morning and decreased it in the afternoon. These findings serve as an important reference for stakeholders to optimise lighting in constructed environments to improve health and well-being considering the non-visual effects above and beyond visual performance. |
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0031-9384 |
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GFZ @ kyba @ |
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3168 |
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Clarke, R.B.; Amini, H.; James, P.; von Euler-Chelpin, M.; Jorgensen, J.T.; Mehta, A.; Cole-Hunter, T.; Westendorp, R.; Mortensen, L.H.; Loft, S.; Brandt, J.; Hertel, O.; Ketzel, M.; Backalarz, C.; Andersen, Z.J.; Lim, Y.-H. |

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Title |
Outdoor light at night and breast cancer incidence in the Danish Nurse Cohort |
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Journal Article |
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Year |
2020 |
Publication |
Environmental Research |
Abbreviated Journal |
Environ Res |
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194 |
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110631 |
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Human health; Remote sensing; Breast neoplasms; Environmental exposure; Female; Incidence; Lighting; Middle-aged; Prospective studies; Risk factors |
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BACKGROUND: Knowledge of the role of melatonin, xenograft experiments, and epidemiological studies suggests that exposure to light at night (LAN) may disturb circadian rhythms, possibly increasing the risk of developing breast cancer. OBJECTIVES: We examined the association between residential outdoor LAN and the incidence of breast cancer: overall and subtypes classified by estrogen (ER) and progesterone (PR) receptor status. METHODS: We used data on 16,941 nurses from the Danish Nurse Cohort who were followed-up from the cohort baseline in 1993 or 1999 through 2012 in the Danish Cancer Registry for breast cancer incidence and the Danish Breast Cancer Cooperative Group for breast cancer ER and PR status. LAN exposure data were obtained from the U.S. Defense Meteorological Satellite Program (DMSP) available for 1996, 1999, 2000, 2003, 2004, 2006, and 2010 in nW/cm(2)/sr unit, and assigned to the study participants' residence addresses during the follow-up. Time-varying Cox regression models were used to calculate the hazard ratios (HRs) and 95% confidence intervals (CIs) for the association between LAN and breast cancer, adjusting for individual characteristics, road traffic noise, and air pollution. RESULTS: Of 16,941 nurses, 745 developed breast cancer in total during 320,289 person-years of follow-up. We found no association between exposure to LAN and overall breast cancer. In the fully adjusted models, HRs for the highest (65.8-446.4 nW/cm(2)/sr) and medium (22.0-65.7 nW/cm(2)/sr) LAN tertiles were 0.97 (95% CI: 0.77, 1.23) and 1.09 (95% CI: 0.90, 1.31), respectively, compared to the lowest tertile of LAN exposure (0-21.9 nW/cm(2)/sr). We found a suggestive association between LAN and ER-breast cancer. CONCLUSION: This large cohort study of Danish female nurses suggests weak evidence of the association between LAN and breast cancer incidence. |
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Section of Environmental Health, Department of Public Health, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark; Seoul National University Medical Research Center, Seoul, Republic of Korea. Electronic address: younhee.lim@sund.ku.dk |
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0013-9351 |
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PMID:33345898 |
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GFZ @ kyba @ |
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3256 |
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Author |
Nehme, P.A.; Amaral, F.; Lowden, A.; Skene, D.J.; Cipolla-Neto, J.; Moreno, C.R.C. |

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Title |
Reduced melatonin synthesis in pregnant night workers: metabolic implications for offspring |
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Journal Article |
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2019 |
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Medical Hypotheses |
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Medical Hypotheses |
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132 |
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109353 |
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Human Health; Pregnancy; Melatonin; Melatonin synthesis; Circadian disruption; shift work |
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Several novel animal studies have shown that intrauterine metabolic programming can be modified in the event of reduced melatonin synthesis during pregnancy, leading to glucose intolerance and insulin resistance in the offspring. It is therefore postulated that female night workers when pregnant may expose the offspring to unwanted health threats. This may be explained by the fact that melatonin is essential for regulating energy metabolism and can influence reproductive activity. Moreover, the circadian misalignment caused by shift work affects fertility and the fetus, increasing the risk of miscarriage, premature birth and low birth weight, phenomena observed in night workers. Thus, we hypothesize that light-induced melatonin suppression as a result of night work may alter intrauterine metabolic programming in pregnant women, potentially leading to metabolic disorders in their offspring. |
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School of Public Health, University of São Paulo, Brazil |
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Elsevier |
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English |
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English |
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0306-9877 |
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GFZ @ kyba @ |
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2610 |
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