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Dose-response relationships for resetting of human circadian clock by lightSince the first report in unicells, studies across diverse species have demonstrated that light is a powerful synchronizer which resets, in an intensity-dependent manner, endogenous circadian pacemakers. Although it is recognized that bright light (approximately 7,000 to 13,000 lux) is an effective circadian synchronizer in humans, it is widely believed that the human circadian pacemaker is insensitive to ordinary indoor illumination (approximately 50-300 lux). It has been proposed that the relationship between the resetting effect of light and its intensity follows a compressive nonlinear function, such that exposure to lower illuminances still exerts a robust effect. We therefore undertook a series of experiments which support this hypothesis and report here that light of even relatively low intensity (approximately 180 lux) significantly phase-shifts the human circadian pacemaker. Our results clearly demonstrate that humans are much more sensitive to light than initially suspected and support the conclusion that they are not qualitatively different from other mammals in their mechanism of circadian entrainment.
Document ID
20040173267
Acquisition Source
Legacy CDMS
Document Type
Reprint (Version printed in journal)
External Source(s)
Authors
Boivin, D. B.
(Brigham and Women's Hospital, Harvard Medical School Boston, Massachusetts 02115, United States)
Duffy, J. F.
Kronauer, R. E.
Czeisler, C. A.
Date Acquired
August 22, 2013
Publication Date
February 8, 1996
Publication Information
Publication: Nature
Volume: 379
Issue: 6565
ISSN: 0028-0836
Subject Category
Aerospace Medicine
Distribution Limits
Public
Copyright
Other
Keywords
NASA Discipline Regulatory Physiology
NASA Discipline Number 18-10
Non-NASA Center
Clinical Trial
NASA Program Space Physiology and Countermeasures

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