The Japanese Association of School Health

Research Paper

ISSN ONLINE : 1880-2400

[School Health Vol.7, 25-34, 2011]

Melatonin Metabolism and Living Conditions among Children on Weekdays and Holidays, and Living Factors Related to Melatonin Metabolism

Shingo Noi* and Akiko Shikano**

  • *Faculty of Education, Saitama University
  • 255 Shimo-Okubo, Sakura-ku, Saitama city, Saitama 338-8570 Japan
  • nois@health.edu.saitama-u.ac.jp
  • **Yokohama Women’s Junior College
  • 4-4-5 Konandai, Minato-ku, Yokohama city, Kanagawa 234-0054 Japan

[Received April 4, 2011 ; Accepted August 31, 2011]

Keywords:
elementary school children, salivary melatonin concentration, biological rhythm, sleeping-wakening

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Abstracts

The purpose of this study was to make clear the aspects of salivary melatonin metabolism and living conditions among school children during weekdays and the day following holidays. Additionally, the purpose was to examine living factors related to melatonin metabolism. The analysis samples were 47 healthy 3rd and 4th grade children in an elementary school. This investigation was carried out during a week in July 2009. Saliva samples were collected three times (6:30pm: evening, 9:30pm: night, 6:30am: morning) at two different periods (weekdays and the day following holidays). Weekdays were from Wednesday to Thursday (weekday-weekday: W-W) and the day following holidays were from Sunday to Monday (holiday-weekday: H-W). Responses to a questionnaire about living conditions were recorded over the course of a week. The results were as follows: 1) Half of the subjects had their highest melatonin concentration at the morning measurement instead of the night measurement. 2) During the W-W period, the percentages of the subjects who had their highest salivary melatonin concentration at the night and morning measurements were not significantly different, and the mean concentrations at the night and morning measurements were also not significantly different. In contrast, during the H-W period, a majority had their highest melatonin concentration at the morning measurement, and the mean concentration was clearly higher at the morning measurement than at the night measurement. 3) Sleeping hours tended to be longer on holidays than on weekdays. Furthermore, bedtimes and wake times were signifi cantly later on holidays than on weekdays. It was also found that electronic media and outdoors play hours were longer on holidays than on weekdays, while study hours were shorter on holidays than on weekdays. 4) Subjects whose salivary melatonin concentration had its highest value at the morning measurement had later bedtimes and wake-times, longer electronic media hours, and shorter outdoor play hours than those whose salivary melatonin concentration had its highest value at the night measurement. These fi ndings suggest that the differences of the living conditions infl uence the melatonin metabolism among the children.

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