title: Late circadian phase in adults and children is correlated with use of high color temperature light at home at night.
abstract: Light is the strongest synchronizer of human circadian rhythms, and exposure to residential light at night reportedly causes a delay of circadian rhythms. The present study was conducted to investigate the association between color temperature of light at home and circadian phase of salivary melatonin in adults and children. Twenty healthy children (mean age: 9.7 year) and 17 of their parents (mean age: 41.9 years) participated in the experiment. Circadian phase assessments were made with dim light melatonin onset (DLMO). There were large individual variations in DLMO both in adults and children. The average DLMO in adults and in children were 21:50 ± 1:12 and 20:55 ± 0:44, respectively. The average illuminance and color temperature of light at eye level were 139.6 ± 82.7 lx and 3862.0 ± 965.6 K, respectively. There were significant correlations between color temperature of light and DLMO in adults (r = 0.735, p < 0.01) and children (r = 0.479, p < 0.05), although no significant correlations were found between illuminance level and DLMO. The results suggest that high color temperature light at home might be a cause of the delay of circadian phase in adults and children.
authors.affiliation: a Department of Human Science, Faculty of Design , Kyushu University , Fukuoka , Japan.|b Physiological Anthropology Research Center , Kyushu University , Fukuoka , Japan.
authors.forename: Shigekazu
authors.initials: S
authors.lastname: Higuchi
authors.affiliation: a Department of Human Science, Faculty of Design , Kyushu University , Fukuoka , Japan.
authors.forename: Sang-il
authors.initials: SI
authors.lastname: Lee
authors.affiliation: a Department of Human Science, Faculty of Design , Kyushu University , Fukuoka , Japan.|b Physiological Anthropology Research Center , Kyushu University , Fukuoka , Japan.
authors.forename: Tomoaki
authors.initials: T
authors.lastname: Kozaki
authors.affiliation: c Laboratory of Environmental Physiology, Faculty of Education , Kochi University , Kochi , Japan.
authors.forename: Tetsuo
authors.initials: T
authors.lastname: Harada
authors.affiliation: a Department of Human Science, Faculty of Design , Kyushu University , Fukuoka , Japan.
authors.forename: Ikuo
authors.initials: I
authors.lastname: Tanaka
mesh_terms: D000328:Adult; D002648:Child; D002940:Circadian Rhythm / Q000502:physiology*; D003116:Color; D005260:Female; D006798:Housing; D006801:Humans; D008027:Light; D008297:Male; D008550:Melatonin / Q000378:metabolism; D008875:Middle Aged; D012890:Sleep / Q000502:physiology*; D013696:Temperature; D055815:Young Adult
chemical_list: D008550:Melatonin
keywords: Children; circadian rhythm; light; melatonin