title: Diurnal variations of hormonal secretion, alertness and cognition in extreme chronotypes under different lighting conditions.
abstract: Circadian rhythms in physiology and behavior are modulated by external factors such as light or temperature. We studied whether self-selected office lighting during the habitual waking period had a different impact on alertness, cognitive performance and hormonal secretion in extreme morning and evening chronotypes (N = 32), whose preferred bed- and wake-up times differed by several hours. The self-selected lighting condition was compared with constant bright light and a control condition in dim light. Saliva samples for hormonal analyses, subjective ratings of alertness, wellbeing, visual comfort and cognitive performance were regularly collected. Between the self-selected and the bright, but not the dim lighting condition, the onset of melatonin secretion in the evening (as marker for circadian phase) was significantly different for both chronotypes. Morning chronotypes reported a faster increase in sleepiness during the day than evening chronotypes, which was associated with higher cortisol secretion. Wellbeing, mood and performance in more difficult cognitive tasks were better in bright and self-selected lighting than in dim light for both chronotypes, whereas visual comfort was best in the self-selected lighting. To conclude, self-selection of lighting at work might positively influence biological and cognitive functions, and allow for inter-individual differences.
authors.affiliation: Ecole Polytechnique Fédérale de Lausanne, Solar Energy and Building Physics Laboratory, CH-1015 Lausanne, Switzerland.|Czech Technical University in Prague, UCEEB, Trinecka 1024, 273 43 Bustehrad, Czech Republic.
authors.forename: L
authors.initials: L
authors.lastname: Maierova
authors.affiliation: Ecole Polytechnique Fédérale de Lausanne, Solar Energy and Building Physics Laboratory, CH-1015 Lausanne, Switzerland.
authors.forename: A
authors.initials: A
authors.lastname: Borisuit
authors.affiliation: Ecole Polytechnique Fédérale de Lausanne, Solar Energy and Building Physics Laboratory, CH-1015 Lausanne, Switzerland.
authors.forename: J-L
authors.initials: JL
authors.lastname: Scartezzini
authors.affiliation: School of Education, University of California, Irvine, USA.
authors.forename: S M
authors.initials: SM
authors.lastname: Jaeggi
authors.affiliation: GIGA-CRC in Vivo Imaging, University of Liège, Belgium.
authors.forename: C
authors.initials: C
authors.lastname: Schmidt
authors.affiliation: Ecole Polytechnique Fédérale de Lausanne, Solar Energy and Building Physics Laboratory, CH-1015 Lausanne, Switzerland.
authors.forename: M
authors.initials: M
authors.lastname: Münch
mesh_terms: D000293:Adolescent; D000328:Adult; D000339:Affect; D001288:Attention; D002940:Circadian Rhythm / Q000502:physiology* / Q000528:radiation effects*; D003071:Cognition; D005260:Female; D006728:Hormones / Q000378:metabolism*; D006801:Humans; D006854:Hydrocortisone / Q000378:metabolism; D008029:Lighting / Q000009:adverse effects; D008297:Male; D008550:Melatonin / Q000378:metabolism; D012463:Saliva / Q000378:metabolism; D012890:Sleep / Q000502:physiology; D014851:Wakefulness; D055815:Young Adult
chemical_list: D006728:Hormones; D008550:Melatonin; D006854:Hydrocortisone