Light-induced melatonin suppression at night after exposure to different wavelength composition of morning light

Tomoaki Kozaki, Ayaka Kubokawa, Ryunosuke Taketomi, Keisuke Hatae

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    39 Citations (Scopus)


    Bright nocturnal light has been shown to suppress melatonin secretion. However, bright light exposure during the day might reduce light-induced melatonin suppression at night. The human circadian system is sensitive to short wavelength light. This study evaluated the preventive effect of different wavelengths of daytime light on light-induced melatonin suppression at night. Twelve male subjects were exposed to various light conditions (dim, white, and bluish white light) between the hours of 09:00 and 10:30 (daytime light conditions). They were then exposed to light (300 lx) again between 01:00 and 02:30 (night-time light exposure). Subjects provided saliva samples before (00:55) and after night-time light exposure (02:30). A two-tailed paired t-test yielded significant decrements in melatonin concentrations after night-time light exposure under daytime dim and white light conditions. No significant differences were found in melatonin concentrations between pre- and post-night-time light exposure with bluish-white light. Present findings suggest that daytime blue light exposure has an acute preventive impact on light-induced melatonin suppression in individuals with a general life rhythm (sleep/wake schedule). These findings may be useful for implementing artificial light environments for humans in, for example, hospitals and underground shopping malls to reduce health risks.

    Original languageEnglish
    Pages (from-to)1-4
    Number of pages4
    JournalNeuroscience Letters
    Publication statusPublished - Mar 11 2016

    All Science Journal Classification (ASJC) codes

    • General Neuroscience


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