Phase advancing the human circadian clock with blue-enriched polychromatic light
Received 14 March 2008; received in revised form 21 May 2008; accepted 27 May 2008.
Abstract
Background
Previous studies have shown that the human circadian system is maximally sensitive to short-wavelength (blue) light. Whether this sensitivity can be utilized to increase the size of phase shifts using light boxes and protocols designed for practical settings is not known. We assessed whether bright polychromatic lamps enriched in the short-wavelength portion of the visible light spectrum could produce larger phase advances than standard bright white lamps.
Methods
Twenty-two healthy young adults received either a bright white or bright blue-enriched 2-h phase advancing light pulse upon awakening on each of four treatment days. On the first treatment day the light pulse began 8h after the dim light melatonin onset (DLMO), on average about 2h before baseline wake time. On each subsequent day, light treatment began 1h earlier than the previous day, and the sleep schedule was also advanced.
Results
Phase advances of the DLMO for the blue-enriched (92±78min, n=12) and white groups (76±45min, n=10) were not significantly different.
Conclusion
Bright blue-enriched polychromatic light is no more effective than standard bright light therapy for phase advancing circadian rhythms at commonly used therapeutic light levels.
aBiological Rhythms Research Laboratory, Rush University Medical Center, Suite 425, 1645 W. Jackson Boulevard, Chicago, IL 60612, USA
bGraduate Division of Neuroscience, Rush University Medical Center, USA
cFaculty of Health and Medical Sciences, University of Surrey, Guildford, Surrey, GU2 7XH, UK
Corresponding author. Address: Biological Rhythms Research Laboratory, Rush University Medical Center, Suite 425, 1645 W. Jackson Boulevard, Chicago, IL 60612, USA. Tel.: +1 312 563 4787; fax: +1 312 563 4900.
ABSTRACT