Light level and duration of exposure determine the impact of self-luminous tablets on melatonin suppression
ABSTRACT Exposure to light from self-luminous displays may be linked to increased risk for sleep disorders because these devices emit optical radiation at short wavelengths, close to the peak sensitivity of melatonin suppression. Thirteen participants experienced three experimental conditions in a within-subjects design to investigate the impact of self-luminous tablet displays on nocturnal melatonin suppression: 1) tablets-only set to the highest brightness, 2) tablets viewed through clear-lens goggles equipped with blue light-emitting diodes that provided 40 lux of 470-nm light at the cornea, and 3) tablets viewed through orange-tinted glasses (dark control; optical radiation <525 nm ≈ 0). Melatonin suppressions after 1-h and 2-h exposures to tablets viewed with the blue light were significantly greater than zero. Suppression levels after 1-h exposure to the tablets-only were not statistically different than zero; however, this difference reached significance after 2 h. Based on these results, display manufacturers can determine how their products will affect melatonin levels and use model predictions to tune the spectral power distribution of self-luminous devices to increase or to decrease stimulation to the circadian system.
- SourceAvailable from: Lisa A. Wines
Chapter: Sleep-Wake and Somatic DisordersA Counselor's Guide to Diagnosis and Treating Children and Adolescent DSM-5 Disorders, Edited by Brande Flamez, Carl J. Sheperis, 01/2015: chapter Sleep-Wake and Somatic Disorders; Wiley.
- [Show abstract] [Hide abstract]
ABSTRACT: Circadian clocks of adolescents typically run late – including sleep times – while adolescents generally are expected at school early in the morning. Due to this mismatch between internal (circadian) and external (social) times, they suffer from chronic sleep deficiency, which, in turn, affects academic performance negatively. This constellation impacts students’ future career prospects. Our study correlates chronotype and exam performance. In total, 4,734 grades were collected from 741 Dutch high school students (ages 11-18 yrs) who had completed the Munich ChronoType Questionnaire (MCTQ) to estimate their internal time. Overall, the lowest grades were obtained by students who were very late chronotypes (MSFsc > 5.31 h) or slept very short on schooldays (SDw < 7.03 h). The effect of chronotype on exam performance depended on the time of day that exams were taken. Opposed to late types, early chronotypes obtained significantly higher grades during the early (8:15-9:45) and late (10:00-12:15) morning. This group difference in grades disappeared in the early afternoon (12:45-15:00). Late types also obtained lower grades than early types when tested at the same internal time (hours after MSFsc), which may reflect general attention and learning disadvantages of late chronotypes during the early morning. Our results support delaying high school starting times as well as scheduling exams in the early afternoon to avoid discrimination of late chronotypes, and to give all high school students equal academic opportunities.Journal of Biological Rhythms 12/2014; 30(1). DOI:10.1177/0748730414564786 · 3.32 Impact Factor
- [Show abstract] [Hide abstract]
ABSTRACT: Both short wavelength (blue) light and caffeine have been studied for their mood enhancing effects on humans. The ability of blue light to increase alertness, mood and cognitive function via non-image forming neuropathways has been suggested as a non-pharmacological countermeasure for depression across a range of occupational settings. This experimental study compared blue light and caffeine and aimed to test the effects of blue light/placebo (BLU), white light/240-mg caffeine (CAF), blue light/240-mg caffeine (BCAF) and white light/placebo (PLA), on mood. A randomised, controlled, crossover design study was used, in a convenience population of 20 healthy volunteers. The participants rated their mood on the Swedish Core Affect Scales (SCAS) prior to and after each experimental condition to assess the dimensions of valence and activation. There was a significant main effect of light (p = 0.009), and the combination of blue light and caffeine had clear positive effects on core effects (ES, ranging from 0.41 to 1.20) and global mood (ES, 0.61 ± 0.53). The benefits of the combination of blue light and caffeine should be further investigated across a range of applications due to the observed effects on the dimensions of arousal, valence and pleasant activation.Psychopharmacology 03/2014; DOI:10.1007/s00213-014-3503-8 · 3.99 Impact Factor