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Melatonin suppression during a simulated night shift in medium intensity light is increased by 10-minute breaks in dim light and decreased by 10-minute breaks in bright light

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Title: Melatonin suppression during a simulated night shift in medium intensity light is increased by 10-minute breaks in dim light and decreased by 10-minute breaks in bright light
Authors: Lee, Sang-Il Browse this author
Kinoshita, Saki Browse this author
Noguchi, Anna Browse this author
Eto, Taisuke Browse this author
Ohashi, Michihiro Browse this author
Nishimura, Yuki Browse this author
Maeda, Kaho Browse this author
Motomura, Yuki Browse this author
Awata, Yasuhiro Browse this author
Higuchi, Shigekazu Browse this author →KAKEN DB
Keywords: Humans
night shift work
intermittent light at night exposure
light adaptation
short duration
melatonin suppression
subjective sleepiness
performance
Issue Date: Jun-2020
Publisher: Taylor & Francis
Journal Title: Chronobiology International
Volume: 37
Issue: 6
Start Page: 897
End Page: 909
Publisher DOI: 10.1080/07420528.2020.1752704
Abstract: Exposure to light at night results in disruption of endogenous circadian rhythmicity and/or suppression of pineal melatonin, which can consequently lead to acute or chronic adverse health problems. In the present study, we investigated whether exposure to very dim light or very bright light for a short duration influences melatonin suppression, subjective sleepiness, and performance during exposure to constant moderately bright light. Twenty-four healthy male university students were divided into two experimental groups: Half of them (mean age: 20.0 +/- 0.9 years) participated in an experiment for short-duration (10 min) light conditions of medium intensity light (430 lx, medium breaks) vs. very dim light (< 1 lx, dim breaks) and the other half (mean age: 21.3 +/- 2.5 years) participated in an experiment for short-duration light conditions of medium intensity light (430 lx, medium breaks) vs. very bright light (4700 lx, bright breaks). Each simulated night shift consisting of 5 sets (each including 50-minute night work and 10-minute break) was performed from 01:00 to 06:00 h. The subjects were exposed to medium intensity light (550 lx) during the night work. Each 10-minute break was conducted every hour from 02:00 to 06:00 h. Salivary melatonin concentrations were measured, subjective sleepiness was assessed, the psychomotor vigilance task was performed at hourly intervals from 21:00 h until the end of the experiment. Compared to melatonin suppression between 04:00 and 06:00 h in the condition of medium breaks, the condition of dim breaks significantly promoted melatonin suppression and the condition of bright breaks significantly diminished melatonin suppression. However, there was no remarkable effect of either dim breaks or bright breaks on subjective sleepiness and performance of the psychomotor vigilance task. Our findings suggest that periodic exposure to light for short durations during exposure to a constant light environment affects the sensitivity of pineal melatonin to constant light depending on the difference between light intensities in the two light conditions (i.e., short light exposure vs. constant light exposure). Also, our findings indicate that exposure to light of various intensities at night could be a factor influencing the light-induced melatonin suppression in real night work settings.
Rights: This is an Accepted Manuscript of an article published by Taylor & Francis in Chronobiology International on June 2020, available online: http://www.tandfonline.com/10.1080/07420528.2020.1752704.
Type: article (author version)
URI: http://hdl.handle.net/2115/81619
Appears in Collections:工学院・工学研究院 (Graduate School of Engineering / Faculty of Engineering) > 雑誌発表論文等 (Peer-reviewed Journal Articles, etc)

Submitter: 李 相逸

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