Many people spend an increasing amount of time in front of computer screens equipped 48 with light emitting diodes (LED) with a short-wavelength (blue range). Thus, we investigated 49 the repercussions on melatonin (a marker of the circadian clock), alertness and cognitive 50 performance levels in 13 young male volunteers under controlled laboratory conditions in a 51 balanced cross-over design. A 5-h evening exposure to a white LED backlit screen with more 52 than twice as much 464 nm light emission [irradiance of 0,241 W/(sr*m 2 ), 2.1 x 10 13 53 photons/(cm 2 *s) in the wavelength range of 454 and 474 nm] than a white non-LED backlit 54 screen [irradiance of 0,099 W/(sr*m 2 ), 0.7 x 10 13 photons/(cm 2 *s) in the wavelength range 55 of 454 and 474 nm] elicited a significant suppression of the evening rise in endogenous 56 melatonin and subjective as well as objective sleepiness as indexed by a reduced incidence 57 of slow eye movements and electroencephalographic low frequency activity (1-7 Hz) in 58 frontal brain regions. Concomitantly, sustained attention as determined by the GO/NOGO 59 task, working memory/attention as assessed by 'explicit timing', and declarative memory 60 performance in a word learning paradigm were significantly enhanced in the LED-backlit 61 screen compared to the non-LED condition. Screen quality and visual comfort were rated the 62 same in both screen conditions, whereas the non-LED screen tended to be considered 63 brighter. Our data indicate that the spectral profile of light emitted by computer screens 64 impacts on circadian physiology, alertness and cognitive performance levels. The challenge 65 will be to design a computer screen whose spectral profile can be individually programmed 66 to add timed, essential light information to the circadian system in humans. 67 68 Keywords (3-5): Non-visual effects of light, spectral analysis, shift work, melatonin, alertness 69 70 by 10.220.33.6 on November 7, 2016 http://jap.physiology.org/ Downloaded from exposure could lead to circadian misalignment and thus eventually to sleep problems (23), 95 depression (19) and even the cardiovascular diseases seen in shift workers (27). 96 Here we investigated the impact of a LED backlit computer screen (enhanced in the short 97 wavelength region, i.e. 460nm) in comparison to a LED-free computer screen on a wide 98 range of measures in human physiology and behavior, such as melatonin levels, cognitive 99 performance and the EEG during wakefulness. Our main prediction was that a 5-h evening 100 exposure to a LED-backlit computer screen, in comparison to a non-LED computer screen, 101 would suppress the evening increase in melatonin levels and evoke an alerting response, 102 with concomitant improvement in cognitive performance. 103 104 Methods 105 Healthy young male volunteers (19 to 35 years) were recruited via advertisements at the 106 University of Basel, Switzerland. Potential study participants filled out questionnaires about 107 their general health, sleep quality (Pittsburgh sleep quality index, PSQI) and their sleep-wake 108 behavior [Munich Chronotype questionnaire, MCTQ (34)]. Volunteers with good sleep 109 quality (PSQI score<5), no extreme chronotype (>3 and <6 points on MCTQ questionnaire), 110 and good general health, underwent a medical examination carried out by the physician in 111 charge and an ophthalmologic examination by a certified optometrist to exclude volunteers 112 with visual impairments, such as color blindness, diminished pupil reaction to light, and a 113 reduced visual field. Participants were not excluded if they wore glasses or contact lenses. 114 Exclusion criteria were smoking, medication or drug consumption, shift work within the last 115 3 months, and transmeridian flights up to 3 months prior to study. Thirteen volunteers 116 (mean age: 23.8 years ± 5.0 SD, mean Body Mass Index: 22.6 ±1.7 SD), were then selected 117 for the study. All subjects gave written informed consent. The study protocol, screening
REF found a significant delay in dim light melatonin onset (DLMO) from evening exposure to LED-backlit computer screens compared to cold cathode fluorescent lamp (CCFL)-backlit computer screens.
Evening exposure to a light-emitting diodes (LED)-backlit computer screen affects circadian physiology and cognitive performance
Journal of applied physiology
Journal of applied physiology
Medicine Chemistry