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Author (up) Higuchi, S.; Fukuda, T.; Kozaki, T.; Takahashi, M.; Miura, N.
Title Effectiveness of a Red-visor Cap for Preventing Light-induced Melatonin Suppression during Simulated Night Work Type Journal Article
Year 2011 Publication Journal of PHYSIOLOGICAL ANTHROPOLOGY Abbreviated Journal J Physiol Anthropol
Volume 30 Issue 6 Pages 251-258
Keywords Human Health
Abstract Bright light at night improves the alertness of night workers. Melatonin suppression induced by light at night is, however, reported to be a possible risk factor for breast cancer. Short-wavelength light has a strong impact on melatonin suppression. A red-visor cap can cut the short-wavelength light from the upper visual field selectively with no adverse effects on visibility. The purpose of this study was to investigate the effects of a red-visor cap on light-induced melatonin suppression, performance, and sleepiness at night. Eleven healthy young male adults (mean age: 21.2±0.9 yr) volunteered to participate in this study. On the first day, the subjects spent time in dim light (<15 lx) from 20:00 to 03:00 to measure baseline data of nocturnal salivary melatonin concentration. On the second day, the subjects were exposed to light for four hours from 23:00 to 03:00 with a nonvisor cap (500 lx), red-visor cap (approx. 160 lx) and blue-visor cap (approx. 160 lx). Subjective sleepiness and performance of a psychomotor vigilance task (PVT) were also measured on the second day. Compared to salivary melatonin concentration under dim light, the decrease in melatonin concentration was significant in a nonvisor cap condition but was not significant in a red-visor cap condition. The percentages of melatonin suppression in the nonvisor cap and red-visor cap conditions at 4 hours after exposure to light were 52.6±22.4% and 7.7±3.3%, respectively. The red-visor cap had no adverse effect on performance of the PVT, brightness and visual comfort, though it tended to increase subjective sleepiness. These results suggest that a red-visor cap is effective in preventing melatonin suppression with no adverse effects on vigilance performance, brightness and visibility.
Address
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Language Summary Language Original Title
Series Editor Series Title Abbreviated Series Title
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ISSN 1880-6791 ISBN Medium
Area Expedition Conference
Notes Approved no
Call Number LoNNe @ christopher.kyba @ Serial 521
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Author (up) Kozaki, T.; Hidaka, Y.; Takakura, J.-Y.; Kusano, Y.
Title Suppression of salivary melatonin secretion under 100-Hz flickering and non-flickering blue light Type Journal Article
Year 2018 Publication Journal of Physiological Anthropology Abbreviated Journal J Physiol Anthropol
Volume 37 Issue 1 Pages 23
Keywords Human Health
Abstract BACKGROUND: Bright light at night is known to suppress melatonin secretion. Novel photoreceptors named intrinsically photosensitive retinal ganglion cells (ipRGCs) are mainly responsible for projecting dark/bright information to the suprachiasmatic nucleus and thus regulating the circadian system. However, it has been shown that the amplitude of the electroretinogram of ipRGCs is considerably lower under flickering light at 100 Hz than at 1-5 Hz, suggesting that flickering light may also affect the circadian system. Therefore, in this study, we evaluated light-induced melatonin suppression under flickering and non-flickering light. METHODS: Twelve male participants between the ages of 20 and 23 years (mean +/- S.D. = 21.6 +/- 1.5 years) were exposed to three light conditions (dim, 100-Hz flickering, and non-flickering blue light) from 1:00 A.M. to 2:30 A.M., and saliva samples were obtained just before 1:00 A.M. and at 1:15, 1:30, 2:00, and 2:30 A.M. RESULTS: A repeated measures t test with Bonferroni correction showed that at 1:15 A.M., melatonin concentrations were significantly lower following exposure to non-flickering light compared with dim light, whereas there was no significant difference between the dim and 100-Hz flickering light conditions. By contrast, after 1:30 A.M., the mean melatonin concentrations were significantly lower under both 100-Hz flickering and non-flickering light than under dim light. CONCLUSION: Although melatonin suppression rate tended to be lower under 100-Hz flickering light than under non-flickering light at the initial 15 min of the light exposure, the present study suggests that 100-Hz flickering light may have the same impact on melatonin secretion as non-flickering light.
Address Department of Health and Nutrition Sciences, Nishikyushu University, Kanzaki, Japan
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Publisher Place of Publication Editor
Language English Summary Language Original Title
Series Editor Series Title Abbreviated Series Title
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ISSN 1880-6791 ISBN Medium
Area Expedition Conference
Notes PMID:30340620 Approved no
Call Number GFZ @ kyba @ Serial 2039
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Author (up) Kozaki, T.; Kubokawa, A.; Taketomi, R.; Hatae, K.
Title Effects of day-time exposure to different light intensities on light-induced melatonin suppression at night Type Journal Article
Year 2015 Publication Journal of Physiological Anthropology Abbreviated Journal J Physiol Anthropol
Volume 34 Issue 1 Pages 27
Keywords Human Health
Abstract BACKGROUND: Bright nocturnal light has been known to suppress melatonin secretion. However, bright light exposure during the day-time might reduce light-induced melatonin suppression (LIMS) at night. The effective proportion of day-time light to night-time light is unclear; however, only a few studies on accurately controlling both day- and night-time conditions have been conducted. This study aims to evaluate the effect of different day-time light intensities on LIMS. METHODS: Twelve male subjects between the ages of 19 and 23 years (mean +/- S.D., 20.8 +/- 1.1) gave informed consent to participate in this study. They were exposed to various light conditions (<10, 100, 300, 900 and 2700 lx) between the hours of 09:00 and 12:00 (day-time light conditions). They were then exposed to bright light (300 lx) again between 01:00 and 02:30 (night-time light exposure). They provided saliva samples before (00:55) and after night-time light exposure (02:30). RESULTS: A one-tailed paired t test yielded significant decrements of melatonin concentration after night-time light exposure under day-time dim, 100- and 300-lx light conditions. No significant differences exist in melatonin concentration between pre- and post-night-time light exposure under day-time 900- and 2700-lx light conditions. CONCLUSIONS: Present findings suggest the amount of light exposure needed to prevent LIMS caused by ordinary nocturnal light in individuals who have a general life rhythm (sleep/wake schedule). These findings may be useful in implementing artificial light environments for humans in, for example, hospitals and underground shopping malls.
Address Graduate School of Design, Kyushu University, 4-9-1 Shiobaru, Fukuoka city, Minami-ku, Japan. hatae.keisuke.725@s.kyushu-u.ac.jp
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Language English Summary Language Original Title
Series Editor Series Title Abbreviated Series Title
Series Volume Series Issue Edition
ISSN 1880-6791 ISBN Medium
Area Expedition Conference
Notes PMID:26141542; PMCID:PMC4491270 Approved no
Call Number LoNNe @ christopher.kyba @ Serial 1210
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Author (up) Lee, S.; Kakitsuba, N.; Katsuura, T.
Title Do green-blocking glasses enhance the nonvisual effects of white polychromatic light? Type Journal Article
Year 2018 Publication Journal of Physiological Anthropology Abbreviated Journal J Physiol Anthropol
Volume 37 Issue 1 Pages 29
Keywords Human Health; Vision
Abstract BACKGROUND: It is well known that light containing the blue component stimulates the intrinsically photosensitive retinal ganglion cells (ipRGCs) and plays a role in melatonin suppression and pupillary constriction. In our previous studies, we verified that simultaneous exposure to blue and green light resulted in less pupillary constriction than blue light exposure. Hence, we hypothesized that the nonvisual effects of polychromatic white light might be increased by blocking the green component. Therefore, we conducted an experiment using optical filters that blocked blue or green component and examined the nonvisual effects of these lights on pupillary constriction and electroencephalogram power spectra. METHODS: Ten healthy young males participated in this study. The participant sat on a chair with his eyes facing an integrating sphere. After 10 min of light adaptation, the participant's left eye was exposed to white pulsed light (1000 lx; pulse width 2.5 ms) every 10 s with a blue-blocking glasses, a green-blocking glasses, or control glasses (no lens), and pupillary constriction was measured. Then, after rest for 10 min, the participant was exposed a continuous white light of 1000 lx with a blue- or green-blocking glasses or control glasses and electroencephalogram was measured. RESULTS: Pupillary constriction with the blue-blocking glasses was significantly less than that observed with the green-blocking glasses. Furthermore, pupillary constriction under the green-blocking glasses was significantly greater than that observed with the control glasses. CONCLUSIONS: A reduction in the green component of light facilitated pupillary constriction. Thus, the effects of polychromatic white light containing blue and green components on ipRGCs are apparently increased by removing the green component.
Address Graduate School of Engineering, Chiba University, Chiba, Japan
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 1880-6791 ISBN Medium
Area Expedition Conference
Notes PMID:30563575; PMCID:PMC6299521 Approved no
Call Number GFZ @ kyba @ Serial 2153
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