Effects of different light intensities in the morning on dim light melatonin onset

Tomoaki Kozaki, Naohiro Toda, Hiroki Noguchi, Akira Yasukouchi

    Research output: Contribution to journalArticlepeer-review

    16 Citations (Scopus)


    The present study evaluated the effects of exposure to light intensity in the morning on dim light melatonin onset (DLMO). The tested light intensities were 750 lux, 150 lux, 3000 lux, 6000 lux and 12,000 lux (horizontal illuminance at cornea), using commercial 5000 K fluorescent lamps. Eleven healthy males aged 21-31 participated in 2-day experiments for each light condition. On the first experimental day (day 1), subjects were exposed to dim light (<30 lux) for 3 h in the morning (09:00-12:00). On the same day, saliva samples were taken in dim light (<30 lux) every 30 min from 21:00 to 01:00 to determine the DLMO phase. The subjects were allowed to sleep from 01:00 to 08:00. On the second experimental day (day 2), the subjects were exposed to experimental light conditions for 3 h in the morning. The experimental schedule after light exposure was the same as on day 1. On comparing day 2 with day 1, significant phase advances of DLMO were obtained at 3000 lux, 6000 lux and 12,000 lux. These findings indicate that exposure to a necessary intensity from an ordinary light source, such as a fluorescent lamp, in the morning within one day affects melatonin secretion.

    Original languageEnglish
    Pages (from-to)97-102
    Number of pages6
    JournalJournal of physiological anthropology
    Issue number3
    Publication statusPublished - 2011

    All Science Journal Classification (ASJC) codes

    • Human Factors and Ergonomics
    • Physiology
    • Orthopedics and Sports Medicine
    • Anthropology
    • Public Health, Environmental and Occupational Health
    • Physiology (medical)


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