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5. ASSOCIATION BETWEEN CIRCADIAN PHASE AND LIGHT BEFORE BEDTIME IN JAPANESE CHILDREN AND THEIR PARENTS

ASSOCIATION BETWEEN CIRCADIAN PHASE AND LIGHT BEFORE BEDTIME IN JAPANESE CHILDREN AND THEIR PARENTS

Higuchi Shigekazu, Lee Sang-il, Nagafuchi Yuki, Harada Kazuki

Department of Human Science, Faculty of Design, Kyushu University, Japan

Higuchi Shigekazu, e-mail: higu-s@design.kyushu-u.ac.jp.

Аннотация

It has been pointed out that the children have short sleep time and late bedtime in some countries. Since we have already reported that photosensitivity to light in children is larger than that in adults, exposure to artificial light at night may be a cause of delayed circadian rhythm in children. In this study, association between lighting condition before bedtime and individual difference in circadian phase in children were examined. Twenty children (9.2±1.9 years) and seventeen of their parents (41.7±5.0 years) volunteered to participate in this study. The study was approved by the local Ethics Research Committee in Kyushu University. Firstly, in an accommodation facility, salivary samples were collected every 30 min from 19:00 to habitual bedtime under dim light (< 15 lx) to measure salivary melatonin concentration. Timing of dim light melatonin onset (DLMO) was determined as a marker of circadian phase. The DLMOs in children and their parents were 20:58 ± 42 min and 21:58 ± 96 min, respectively. The DLMO in children was significantly correlated with that in their parents. This suggests that circadian rhythm of parents can affect that of children. Next, the illuminance level and color temperature of light was measured at home in each participant by themselves. The average and standard deviation of vertical illuminance level at their eye level and color temperature of light was 140.0 ± 82.7 lx and 3862.0 ± 965.6 K, respectively. Interestingly, there were significant positive correlations between DLMO and color temperature in adults and children although illuminance level was not significantly correlated with the DLMO. These results suggest that circadian phase of children is affected not only by circadian rhythm of parents but also by color temperature of light before bedtime in Japan.

Ключевые слова

circadian rhythm, melatonin, sleep, children, light at night

Цит.: Higuchi Shigekazu, Lee Sang-il, Nagafuchi Yuki, Harada Kazuki ASSOCIATION BETWEEN CIRCADIAN PHASE AND LIGHT BEFORE BEDTIME IN JAPANESE CHILDREN AND THEIR PARENTS // Вестник Московского университета. Серия XXIII. Антропология, 2014; 3/2014; с. 129-129