title: Entrainment of a free-running human with bright light?
abstract: The case of a 40-year-old sighted woman with free-running sleep-wake and melatonin rhythms is presented. The subject was studied for 102 days. During the pre-treatment period, both the sleep-wake and melatonin rhythms had a period of 25.1 hr, similar to the average period of humans living in temporal isolation. Treatment consisted of bright artificial light exposure (2500 lx Vita-Lite) for 2 hr each day upon awakening. Clock time of light exposure was held constant for 6 days and then slowly advanced until the subject was arising at her desired time of day. The subject continued the light treatment at home and was able to live on a 24-hr day for the 30-day follow-up study. While other factors may be operating in this situation, it is possible that the light treatment caused the stabilization of the free-running rhythms, advancement to a normal phase and entrainment to the 24-hr day. We suspect that the tendency to free-run was related to sleep onsets that were abnormally delayed relative to the circadian phase response curve for light. By scheduling a 2-hr pulse of bright light each morning, this tendency to delay would be counteracted by light-induced advances, resulting in normal entrainment.
authors.affiliation: Department of Psychiatry, Oregon Health Sciences University, Portland 97201.
authors.forename: T M
authors.initials: TM
authors.lastname: Hoban
authors.forename: R L
authors.initials: RL
authors.lastname: Sack
authors.forename: A J
authors.initials: AJ
authors.lastname: Lewy
authors.forename: L S
authors.initials: LS
authors.lastname: Miller
authors.forename: C M
authors.initials: CM
authors.lastname: Singer
mesh_terms: D000328:Adult; D002940:Circadian Rhythm / Q000502:physiology / Q000528:radiation effects*; D005260:Female; D006801:Humans; D008027:Light; D008550:Melatonin / Q000097:blood; D010789:Phototherapy; D012890:Sleep / Q000502:physiology / Q000528:radiation effects
chemical_list: D008550:Melatonin