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Physiol Rep. 2018 Dec;6(24):e13942. doi: 10.14814/phy2.13942.

Melatonin suppression and sleepiness in children exposed to blue-enriched white LED lighting at night.

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Department of Human Science, Faculty of Design, Kyushu University, Fukuoka, Japan.
Laboratory of Environmental Ergonomics, Faculty of Engineering, Hokkaido University, Sapporo, Japan.
Graduate School of Integrated Frontier Sciences, Kyushu University, Fukuoka, Japan.
Research Fellow of the Japan Society for the Promotion of Science, Fukuoka, Japan.


Light-induced melatonin suppression in children is reported to be more sensitive to white light at night than that in adults; however, it is unclear whether it depends on spectral distribution of lighting. In this study, we investigated the effects of different color temperatures of LED lighting on children's melatonin secretion during the night. Twenty-two healthy children (8.9 ± 2.2 years old) and 20 adults (41.7 ± 4.4 years old) participated in this study. A between-subjects design with four combinations, including two age groups (adults and children) and the two color temperature conditions (3000 K and 6200 K), was used. The experiment was conducted for two consecutive nights. On the first night, saliva samples were collected every hour under a dim light condition (<30 lx). On the second night, the participants were exposed to either color temperature condition. Melatonin suppression in children was greater than that in adults at both 3000 K and 6200 K condition. The 6200 K condition resulted in greater melatonin suppression than did the 3000 K condition in children (P < 0.05) but not in adults. Subjective sleepiness in children exposed to 6200 K light was significantly lower than that in children exposed to 3000 K light. In children, blue-enriched LED lighting has a greater impact on melatonin suppression and it inhibits the increase in sleepiness during night. Light with a low color temperature is recommended at night, particularly for children's sleep and circadian rhythm.


Child; circadian rhythm; color temperature; light; sleep

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