title: Evening use of light-emitting eReaders negatively affects sleep, circadian timing, and next-morning alertness.
abstract: In the past 50 y, there has been a decline in average sleep duration and quality, with adverse consequences on general health. A representative survey of 1,508 American adults recently revealed that 90% of Americans used some type of electronics at least a few nights per week within 1 h before bedtime. Mounting evidence from countries around the world shows the negative impact of such technology use on sleep. This negative impact on sleep may be due to the short-wavelength-enriched light emitted by these electronic devices, given that artificial-light exposure has been shown experimentally to produce alerting effects, suppress melatonin, and phase-shift the biological clock. A few reports have shown that these devices suppress melatonin levels, but little is known about the effects on circadian phase or the following sleep episode, exposing a substantial gap in our knowledge of how this increasingly popular technology affects sleep. Here we compare the biological effects of reading an electronic book on a light-emitting device (LE-eBook) with reading a printed book in the hours before bedtime. Participants reading an LE-eBook took longer to fall asleep and had reduced evening sleepiness, reduced melatonin secretion, later timing of their circadian clock, and reduced next-morning alertness than when reading a printed book. These results demonstrate that evening exposure to an LE-eBook phase-delays the circadian clock, acutely suppresses melatonin, and has important implications for understanding the impact of such technologies on sleep, performance, health, and safety.
authors.affiliation: Division of Sleep and Circadian Disorders, Departments of Medicine and Neurology, Brigham and Women's Hospital, Boston, MA 02115; Division of Sleep Medicine, Harvard Medical School, Boston, MA 02115; and amchang@psu.edu.
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, MA 02115; Division of Sleep Medicine, Harvard Medical School, Boston, MA 02115; and Institute of Aerospace Medicine, German Aerospace Center, 51147 Cologne, Germany.
authors.forename: Daniel
authors.initials: D
authors.lastname: Aeschbach
authors.affiliation: Division of Sleep and Circadian Disorders, Departments of Medicine and Neurology, Brigham and Women's Hospital, Boston, MA 02115; Division of Sleep Medicine, Harvard Medical School, Boston, MA 02115; and.
authors.forename: Jeanne F
authors.initials: JF
authors.lastname: Duffy
authors.affiliation: Division of Sleep and Circadian Disorders, Departments of Medicine and Neurology, Brigham and Women's Hospital, Boston, MA 02115; Division of Sleep Medicine, Harvard Medical School, Boston, MA 02115; and.
authors.forename: Charles A
authors.initials: CA
authors.lastname: Czeisler
mesh_terms: D000328:Adult; D002940:Circadian Rhythm; D005260:Female; D006801:Humans; D008029:Lighting / Q000009:adverse effects*; D008297:Male; D008550:Melatonin / Q000097:blood; D011932:Reading; D012890:Sleep; D012893:Sleep Wake Disorders / Q000097:blood / Q000503:physiopathology*
chemical_list: D008550:Melatonin
keywords: chronobiology; digital media; electronics; phase-shifting; sleep