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Author (up) Kozaki, T.; Kubokawa, A.; Taketomi, R.; Hatae, K. url  doi
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  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  
  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:26141542; PMCID:PMC4491270 Approved no  
  Call Number LoNNe @ christopher.kyba @ Serial 1210  
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