title: Circadian phase resetting by a single short-duration light exposure.
abstract: BACKGROUND.In humans, a single light exposure of 12 minutes and multiple-millisecond light exposures can shift the phase of the circadian pacemaker. We investigated the response of the human circadian pacemaker to a single 15-second or 2-minute light pulse administered during the biological night.METHODS.Twenty-six healthy individuals participated in a 9-day inpatient protocol that included assessment of dim light melatonin onset time (DLMO time) before and after exposure to a single 15-second (n= 8) or 2-minute (n= 12) pulse of bright light (9,500 lux; 4,100 K fluorescent) or control background dim light (<3 lux;n= 6). Phase shifts were calculated as the difference in clock time between the two phase estimates.RESULTS.Both 15-second and 2-minute exposures induced phase delay shifts [median (± SD)] of -34.8 ± 47.2 minutes and -45.4 ± 28.4 minutes, respectively, that were significantly (P= 0.04) greater than the control condition (advance shift: +22.3 ± 51.3 minutes) but were not significantly different from each other. Comparisons with historic data collected under the same conditions confirmed a nonlinear relationship between exposure duration and the magnitude of phase shift.CONCLUSIONS.Our results underscore the exquisite sensitivity of the human pacemaker to even short-duration single exposures to light. These findings may have real-world implications for circadian disruption induced by exposure to brief light stimuli at night.TRIAL REGISTRATION.The study was registered as a clinical trial on www.clinicaltrials.org, NCT #01330992.FUNDING.Funding for this study was provided by NSBRI HFP02802 and NIH P01-AG09975, R01-HL114088 (EBK), RC2-HL101340-0 (EBK, SWL, SAR, REK), K02-HD045459 (EBK), K24-HL105664 (EBK), T32-HL07901 (MSH, SAR), HL094654 (CAC), and AG044416 (JFD). The project described was supported by NIH grant 1UL1 TR001102-01, 8UL1TR000170-05, UL1 RR 025758, Harvard Clinical and Translational Science Center, from the National Center for Advancing Translational Science.
authors.affiliation: Division of Sleep and Circadian Disorders, Departments of Medicine and Neurology, Brigham and Women's Hospital, Boston, Massachusetts, USA.|Division of Sleep Medicine, Harvard Medical School, Boston, Massachusetts, USA.
authors.forename: Shadab A
authors.initials: SA
authors.lastname: Rahman
authors.affiliation: Division of Sleep and Circadian Disorders, Departments of Medicine and Neurology, Brigham and Women's Hospital, Boston, Massachusetts, USA.|Division of Sleep Medicine, Harvard Medical School, Boston, Massachusetts, USA.
authors.forename: Melissa A
authors.initials: MA
authors.lastname: St Hilaire
authors.affiliation: Division of Sleep and Circadian Disorders, Departments of Medicine and Neurology, Brigham and Women's Hospital, Boston, Massachusetts, USA.|Division of Sleep Medicine, Harvard Medical School, Boston, Massachusetts, USA.
authors.forename: Anne-Marie
authors.initials: AM
authors.lastname: Chang
authors.affiliation: Division of Sleep and Circadian Disorders, Departments of Medicine and Neurology, Brigham and Women's Hospital, Boston, Massachusetts, USA.|Division of Sleep Medicine, Harvard Medical School, Boston, Massachusetts, USA.|Surrey Sleep Research Centre, Faculty of Health and Medical Sciences, University of Surrey, Guildford, Surrey, United Kingdom.
authors.forename: Nayantara
authors.initials: N
authors.lastname: Santhi
authors.affiliation: Division of Sleep and Circadian Disorders, Departments of Medicine and Neurology, Brigham and Women's Hospital, Boston, Massachusetts, USA.|Division of Sleep Medicine, Harvard Medical School, Boston, Massachusetts, USA.
authors.forename: Jeanne F
authors.initials: JF
authors.lastname: Duffy
authors.affiliation: Division of Sleep Medicine, Harvard Medical School, Boston, Massachusetts, USA.|School of Engineering and Applied Science, Harvard University, Cambridge, Massachusetts, USA.
authors.forename: Richard E
authors.initials: RE
authors.lastname: Kronauer
authors.affiliation: Division of Sleep and Circadian Disorders, Departments of Medicine and Neurology, Brigham and Women's Hospital, Boston, Massachusetts, USA.|Division of Sleep Medicine, Harvard Medical School, Boston, Massachusetts, USA.
authors.forename: Charles A
authors.initials: CA
authors.lastname: Czeisler
authors.affiliation: Division of Sleep and Circadian Disorders, Departments of Medicine and Neurology, Brigham and Women's Hospital, Boston, Massachusetts, USA.|Division of Sleep Medicine, Harvard Medical School, Boston, Massachusetts, USA.
authors.forename: Steven W
authors.initials: SW
authors.lastname: Lockley
authors.affiliation: Division of Sleep and Circadian Disorders, Departments of Medicine and Neurology, Brigham and Women's Hospital, Boston, Massachusetts, USA.|Division of Sleep Medicine, Harvard Medical School, Boston, Massachusetts, USA.
authors.forename: Elizabeth B
authors.initials: EB
authors.lastname: Klerman
mesh_terms: D000222:Adaptation, Physiological; D000328:Adult; D002940:Circadian Rhythm / Q000528:radiation effects*; D005260:Female; D064368:Healthy Volunteers; D006801:Humans; D008027:Light; D008297:Male; D008550:Melatonin / Q000097:blood*; D012890:Sleep / Q000528:radiation effects; D013997:Time Factors; D055815:Young Adult
chemical_list: D008550:Melatonin