Caffeine does not entrain the circadian clock but improves daytime alertness in blind patients with non-24-hour rhythms.

"Conflict of interest Neither author has any conflicts of interest directly associated with the current study. Dr. Lockley was the principal investigator of two recently completed and one ongoing sponsored clinical trials of a melatonin agonist for the treatment of non-24-hour sleep–wake disorder in the blind, sponsored by Vanda Pharmaceuticals. Inc., and has received an investigator-initiated research grant and two service agreements from Vanda Pharmaceuticals, Inc., related to non-24-hour rhythms in the blind. He has also received minor consulting fees from 14 financial companies related to non-24-hour sleep–wake disorder in the blind and the publicly available clinical trial results. He has also received honoraria from MediCom Worldwide, Inc., for teaching on a CME course sponsored by Vanda Pharmaceuticals, Inc.; for contributing text about non-24-hour sleep–wake disorder for the National Sleep Foundation and textbook chapters published by Elsevier; and in 2007 received an authorship fees from Servier Inc., for writing a review of circadian rhythm disorders in the blind. Dr. Lockley also reports receiving consulting fees in the past from American Family, Apollo Lighting, Brigham and Women's Hospital, Naturebright, Thomas Jefferson University, Warwick Medical School, and Wyle Integrated Science and Engineering and Wyvern Funds; and holds current consulting contracts with Headwaters, PlanLED and Wyle Integrated Science and Engineering; unrestricted equipment gifts from Bioilluminations LLC, Bionetics Corporation, and ResMed Inc.; an unrestricted monetary gift to support research from Swinburne University of Technology, Australia; a fellowship gift from Optalert, Pty, Melbourne, Australia; equity in iSLEEP, Pty, Melbourne, Australia; advance author payment and royalties from Oxford University Press; honoraria for written articles by AMO Inc., and the Wall Street Journal; honoraria plus travel, accommodation or meals for invited seminars, conference presentations or teaching from 2nd International Symposium on the Design of Artificial Environments; American Society for Photobiology; Bassett Research Institute; Brookline Adult Education; Brown University; Emergency Social Services Association Conference; Harvard University (CME); I Slept Great/Euforma, LLC; International Graduate School of Neuroscience; Japan National Institute of Occupational Safety and Health; Lightfair; North East Sleep Society; Notre Dame University; Takeda Pharmaceuticals North America; Thomas Jefferson University; University of Vermont College of Medicine; Velux; travel and accommodation support (no honoraria) for invited seminars, conference presentations or teaching from 8th International Conference on Managing Fatigue; 14th Annual Tennessee Perfusion Conference; American Academy of Sleep Medicine; Apollo Lighting; Bar Harbor Chamber of Commerce; Canadian Sleep Society; Committee of Interns and Residents; Coney Island Hospital; Connecticut Business & Industry Association Health and Safety Conference; Emergency Services Steering Committee; FASEB; Ferrari; Harvard University; Illinois Coalition for Responsible Outdoor Lighting; Lighting Science Group Corp; Massachusetts General Hospital; National Research Council Canada; New England College of Occupational and Environmental Medicine; New York Academy of Sciences; Ontario Association of Fire Chiefs; Oxford University; Philips Lighting; Rio Tinto; Sleep HealthCenters; UMass Memorial; University of Manchester; University of Montreal; University of Texas Medical Branch; University of Tsukuba; Vanda Pharmaceuticals Inc.; Warwick Medical School; Woolcock Institute of Medical Research; Wyle Integrated Science and Engineering (NASA). Dr. Lockley has completed investigator-initiated research grants from Alcon Inc, and Apollo Lighting and has ongoing investigator-initiated research grants from Biological Illuminations LLC, and Respironics Inc., has a service agreement with Rio Tinto Iron Ore; and has received two investigator-initiated research grants from the ResMed Foundation. Dr. Lockley holds a process patent for the use of short-wavelength light for resetting the human circadian pacemaker and improving alertness and performance which is assigned to the Brigham and Women's Hospital per Hospital policy. He has also received minor revenue from a patent on the use of short-wavelength light which is assigned to the University of Surrey. Dr. Lockley has also served as a paid expert on behalf of six public bodies and one union on arbitrations related to sleep, circadian rhythms, and work hours. The ICMJE Uniform Disclosure Form for Potential Conflicts of Interest associated with this article can be viewed by clicking on the following link: http://dx.doi.org/10.1016/j.sleep.2015.01.018. Conflict of interestICMJE Form for Disclosure of Potential Conflicts of Interest form. Conflict of interest ICMJE Form for Disclosure of Potential Conflicts of Interest form."

"We thank Debra J. Skene, Ph.D., Josephine Arendt, Ph.D., John Wright, M.B.B.S., Benita Middleton, Ph.D., and James Tollerfield at the University of Surrey for their assistance with this study. S.W.L. was supported by a fellowship from The Wellcome Trust, UK (060018/B/99/Z). M.A.S.H. was supported by a National Heart, Lung, and Blood Institute fellowship in the program of training in Sleep, Circadian and Respiratory Neurobiology at Brigham and Women's Hospital (T32 HL079010)."