title: The effect of polarized versus nonpolarized light on melatonin regulation in humans.
abstract: The aim of this study was to compare the effects of polarized light versus nonpolarized light on melatonin secretion in healthy, humans (mean age, 25 years; N = 6). On separate evenings, each subject was exposed to four different light intensities (20, 40, 80 and 3200 lx) of both polarized and nonpolarized light, as well as to a control, dark exposure. Each evening experiment consisted of a 120 min dark exposure (0000-0200 h) followed by a 90 min light exposure (0200-0330 h). Subjects' pupils were dilated prior to exposures. Blood samples were drawn at the start and end of each light-exposure period and later assayed for melatonin by radioimmunoassay. When compared to control exposures, both polarized and nonpolarized light elicited significant suppression of plasma melatonin at each illuminance (P < 0.03 to P < 0.0001), There were no significant differences between the effects of polarized light and nonpolarized light at any illuminance. The two light stimuli modalities demonstrated very similar fluence-response relationships between illuminance and melatonin suppression. Thus, the human pineal gland is responsive to ocular exposure with polarized light in a dose-dependent manner similar to that of nonpolarized light, although no significant differences were detected between polarized and nonpolarized light on melatonin regulation.
authors.affiliation: Department of Neurology, Jefferson Medical College, Thomas Jefferson University, Philadelphia, PA 19107-5083, USA. george.brainard/mail.tju.edu
authors.forename: G C
authors.initials: GC
authors.lastname: Brainard
authors.forename: M D
authors.initials: MD
authors.lastname: Rollag
authors.forename: J P
authors.initials: JP
authors.lastname: Hanifin
authors.forename: G
authors.initials: G
authors.lastname: van den Beld
authors.forename: B
authors.initials: B
authors.lastname: Sanford
mesh_terms: D000328:Adult; D005260:Female; D006801:Humans; D008027:Light; D008297:Male; D008550:Melatonin / Q000097:blood / Q000502:physiology*
chemical_list: D008550:Melatonin