title: The effect of bright light on physiological circadian rhythms and subjective alertness of shift work nurses in Iran.
abstract: In this study, the effects of bright light (BL) on the rhythms in body temperature, plasma melatonin, plasma cortisol and subjective alertness, in 34 shift work nurses at a university hospital were assessed. They were exposed to very BL (4,500 lx) during 2 breaks (21:15-22:00 and 3:15-4:00) or dim light (300 lx). The subjects were studied under 24 h of realistic conditions during which their plasma cortisol and melatonin were measured at 3-h intervals; their body temperature was also measured during and after night shift work. Subjective alertness was evaluated with the Karolinska sleepiness scale. Administration of BL significantly suppressed night-time melatonin levels. A one-way ANOVA revealed that BL tended to increase cortisol levels and body temperature and significantly improved alertness. These results demonstrate that photic stimulation in a hospital setting can have a powerful influence on the adjustment of the circadian system.
authors.affiliation: School of Public Health, Tehran University of Medical Sciences, Tehran, Iran. hkakooei@sina.tums.ac.ir
authors.forename: Hossein
authors.initials: H
authors.lastname: Kakooei
authors.forename: Zahra Zamanian
authors.initials: ZZ
authors.lastname: Ardakani
authors.forename: Mohammad Taghi
authors.initials: MT
authors.lastname: Ayattollahi
authors.forename: Mortaza
authors.initials: M
authors.lastname: Karimian
authors.forename: Gebraeil Nasl
authors.initials: GN
authors.lastname: Saraji
authors.forename: Ali Akbar
authors.initials: AA
authors.lastname: Owji
mesh_terms: D000704:Analysis of Variance; D001831:Body Temperature; D002940:Circadian Rhythm; D005260:Female; D006785:Hospitals, University; D006801:Humans; D006854:Hydrocortisone / Q000097:blood; D007492:Iran; D008029:Lighting; D008550:Melatonin / Q000097:blood; D009741:Nursing Staff, Hospital; D010775:Photic Stimulation; D014940:Work Schedule Tolerance
chemical_list: D008550:Melatonin; D006854:Hydrocortisone