title: Influences of twilight on diurnal variation of core temperature, its nadir, and urinary 6-hydroxymelatonin sulfate during nocturnal sleep and morning drowsiness.
abstract: This study aimed at elucidating the physiological significance of dusk and dawn in the circadian rhythm of core temperature (T(core)) and urinary 6-hydroxymelatonin sulfate in humans during sleep and the waking sensation just after rising. Seven female and four male students served as participants. Participants retired at 2300 h and rose at 0700 h. They were requested to sit on a chair and spend time as quietly as possible during wakefulness, reading a book or listening to recorded light music. Two lighting conditions were provided for each participant: 1) Light-Dark (LD)-rectangular light change with abrupt decrease from 3,000 lx to 100 lx at 1800 h, abrupt increase from 0 lx to 3,000 lx at 0700 h. 2) LD-twilight light change with gradual decrease from 3,000 lx to 100 lx starting at 1700 h (twilight period about 2 h), with gradual increase from 0 lx to 3,000 lx starting at 0500 h (twilight period about 2 h). The periods of 0 lx at night were from 2300 h to 0700 h on the first day and from 2300 to 0500 h on the second day. Nadir time advanced significantly under the influence of the LD-twilight condition. The amount of 6-hydroxymelatonin sulfate in urine collected at 0200 h was significantly higher under LD-twilight in comparison with LD-rectangular light. Morning drowsiness tended to be lower under LD-twilight. Our results suggest that in architectural design of indoor illumination it is important to provide LD-twilight in the evening and early morning for sleep promotion in healthy normal people and/or light treatment in elderly patients with advanced dementia.
authors.affiliation: Heart-ful Living R&D Institute, Comprehensive Housing R&D Institute, Sekisui House Ltd., Kyoto, Japan. kondo@gz.sekisuihouse.co.jp
authors.forename: Masayuki
authors.initials: M
authors.lastname: Kondo
authors.forename: Hiromi
authors.initials: H
authors.lastname: Tokura
authors.forename: Tomoko
authors.initials: T
authors.lastname: Wakamura
authors.forename: Ki-Ja
authors.initials: KJ
authors.lastname: Hyun
authors.forename: Satoshi
authors.initials: S
authors.lastname: Tamotsu
authors.forename: Takeshi
authors.initials: T
authors.lastname: Morita
authors.forename: Tadashi
authors.initials: T
authors.lastname: Oishi
mesh_terms: D000293:Adolescent; D000328:Adult; D001831:Body Temperature / Q000502:physiology*; D002940:Circadian Rhythm; D005260:Female; D006801:Humans; D008027:Light; D008297:Male; D008550:Melatonin / Q000031:analogs & derivatives* / Q000652:urine; D012890:Sleep / Q000502:physiology*; D012894:Sleep Stages / Q000502:physiology*
chemical_list: C054513:6-sulfatoxymelatonin; D008550:Melatonin