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Human responses to bright light of different durations

Chang, A.-M., Santhi, N., St Hilaire, M., Gronfier, C., Bradstreet, D.S., Duffy, J.F., Lockley, S.W., Kronauer, R.E. and Czeisler, C.A. (2012) Human responses to bright light of different durations Journal of Physiology, 590 (13). pp. 3103-3112.

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Abstract

Light exposure in the early night induces phase delays of the circadian rhythm in melatonin in humans. Previous studies have investigated the effect of timing, intensity, wavelength, history and pattern of light stimuli on the human circadian timing system. We present results from a study of the duration-response relationship to phase-delaying bright light. Thirty-nine young healthy participants (16 female; 22.18 ± 3.62 years) completed a 9-day inpatient study. Following three baseline days, participants underwent an initial circadian phase assessment procedure in dim light (<3 lux), and were then randomized for exposure to a bright light pulse (~10,000 lux) of 0.2 h, 1.0 h, 2.5 h or 4.0 h duration during a 4.5 h controlled-posture episode centred in a 16 h wake episode. After another 8 h sleep episode, participants completed a second circadian phase assessment. Phase shifts were calculated from the difference in the clock time of the dim light melatonin onset (DLMO) between the initial and final phase assessments. Exposure to varying durations of bright light reset the circadian pacemaker in a dose-dependent, non-linear manner. Per minute of exposure, the 0.2 h duration was over 5 times more effective at phase delaying the circadian pacemaker (1.07 ± 0.36 h) as compared with the 4.0 h duration (2.65 ± 0.24 h). Acute melatonin suppression and subjective sleepiness also had a dose-dependent response to light exposure duration. These results provide strong evidence for a non-linear resetting response of the human circadian pacemaker to light duration. © 2012 The Authors. The Journal of Physiology © 2012 The Physiological Society.

Item Type: Article
Authors :
NameEmailORCID
Chang, A.-M.
Santhi, N.
St Hilaire, M.
Gronfier, C.
Bradstreet, D.S.
Duffy, J.F.
Lockley, S.W.s.lockley@surrey.ac.uk
Kronauer, R.E.
Czeisler, C.A.
Date : 2012
DOI : 10.1113/jphysiol.2011.226555
Uncontrolled Keywords : melatonin, adult, alertness, article, bright light, circadian rhythm, controlled study, female, human, human experiment, light, light exposure, male, normal human, priority journal, somnolence, time, Adolescent, Adult, Circadian Rhythm, Female, Humans, Light, Male, Melatonin, Sleep, Time Factors, Young Adult
Depositing User : Clive Harris
Date Deposited : 17 Jun 2020 01:43
Last Modified : 17 Jun 2020 01:43
URI: http://epubs.surrey.ac.uk/id/eprint/857907

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