0062 EVENING LIGHT EXPOSURE FROM COMPUTER SCREENS DISRUPTS SLEEP, BIOLOGICAL RHYTHMS, AND ATTENTION ABILITIES

• Published in: Sleep (New York, N.Y.) N.Y.), 2017-04, Vol.40 (suppl_1), p.A24-A24
• Main Authors: Green, A, Cohen-Zion, M, Haim, A, Dagan, Y
• Format: Article
• Language: English
• Subjects: Biological rhythms; Light; Melatonin; Sleep
• ISSN: 0161-8105; 1550-9109
• DOI: 10.1093/sleepj/zsx050.061

Abstract Introduction: Millions of computers, tablets, and smart-phones are bought worldwide every month and usage time of these devices is increasing constantly. As a result, humans are almost continuously exposed to unintentional artificial light at night (ALAN) from these device screens. We explored the independent and combined effects of two aspects of screen illumination, light wavelength and intensity, on sleep, its biological regulation, and related functional outcomes, including sleepiness, mood, and attention. Methods: A 2x2 repeated measures design with two independent variables: screen light intensity (low ([LI]: 80 lux and high [HI]: 350 lux) and light wavelength (short [SWL]: 460nm and long [LWL]: 620nm). Nineteen healthy participants (11F; mean age 24.3 [±2.8] years) underwent four experimental light conditions, namely LI/SWL, HI/SWL, LI/LWL and HI/LWL, in counterbalanced order. Each light exposure lasted for 2 hours (21:00-23:00) during which participants performed onscreen tasks. After each exposure, participants underwent an overnight PSG in the laboratory where oral temperature and urine samples (for melatonin analysis) were collected at multiple time points during the night and morning. Each morning participants filled out mood and sleepiness measures and conducted a computerized attention task. Results: Irrespective of light intensity, SWL illumination significantly disrupted sleep continuity (decreased TST and SE and increased SOL, WASO) and architecture (increased stages 1 and 2 sleep, and decreased SWS). When compared to LWL, SWL also significantly altered biological rhythms by subduing the normal decline in body temperature at night and dampening nocturnal melatonin secretion. Light intensity seemed to independently affect sleep as well, but to a lesser degree. SWL exposure led to greater self-reported sleepiness, when compared to LWL. Light exposure negatively affected morning attention, with SWL reducing response accuracy, while light intensity slowed reaction time (RT). Mood was not significantly affected by light intensity or wavelength. Conclusion: Light wavelength seems to have a greater influence than light intensity on a wide-range of biological and behavioral measures. Given the widespread use of electronic devices today, particularly in the evening and nighttime, our findings suggest that ALAN may have detrimental effects on our health and daily functions. Support (If Any): No support.