title: Exposure to long summer days affects the human melatonin and cortisol rhythms.
abstract: Exposure of 8 human subjects in summer to a natural 16 h bright light photoperiod phase advanced the morning salivary melatonin decline and cortisol rise and shortened the nocturnal melatonin signal by 2 h relative to the winter patterns of the same subjects followed under a combined artificial and natural light 16 h photoperiod. The data suggest that summer days experienced from sunrise till sunset and not winter days with a combined artificial and natural light long photoperiod evoke a true long day response of the human circadian system.
authors.affiliation: Institute of Physiology, Academy of Sciences of the Czech Republic, Prague.
authors.forename: D
authors.initials: D
authors.lastname: Vondrasová
authors.forename: I
authors.initials: I
authors.lastname: Hájek
authors.forename: H
authors.initials: H
authors.lastname: Illnerová
mesh_terms: D000293:Adolescent; D002940:Circadian Rhythm; D005260:Female; D006801:Humans; D006854:Hydrocortisone / Q000378:metabolism*; D008029:Lighting; D008297:Male; D008550:Melatonin / Q000378:metabolism*; D017440:Photoperiod; D012463:Saliva / Q000378:metabolism / Q000528:radiation effects; D012621:Seasons; D013472:Sunlight
chemical_list: D008550:Melatonin; D006854:Hydrocortisone