Neuropsychological Function Response to Nocturnal Blue Light Blockage in Individuals With Symptoms of Insomnia: A Pilot Randomized Controlled Study

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Abstract

Objectives: Insomnia is associated with neuropsychological dysfunction. Evidence points to the role of nocturnal light exposure in disrupted sleep patterns, particularly blue light emitted through smartphones and computers used before bedtime. This study aimed to test whether blocking nocturnal blue light improves neuropsychological function in individuals with insomnia symptoms. Methods: This study used a randomized, placebo-controlled crossover design. Participants were randomly assigned to a 1-week intervention with amber lenses worn in wrap-around frames (to block blue light) or a 1-week intervention with clear lenses (control) and switched conditions after a 4-week washout period. Neuropsychological function was evaluated with tests from the NIH Toolbox Cognition Battery at three time points: (1) baseline (BL), (2) following the amber lenses intervention, and (3) following the clear lenses intervention. Within-subjects general linear models contrasted neuropsychological test performance following the amber lenses and clear lenses conditions with BL performance. Results: Fourteen participants (mean(standard deviation, SD): age = 46.5(11.4)) with symptoms of insomnia completed the protocol. Compared with BL, individuals performed better on the List Sorting Working Memory task after the amber lenses intervention, but similarly after the clear lenses intervention ( F = 5.16; p = .014; η ² = 0.301). A similar pattern emerged on the Pattern Comparison Processing Speed test ( F = 7.65; p = 0.002; η ² = 0.370). Consideration of intellectual ability indicated that treatment with amber lenses “normalized” performance on each test from approximately 1 SD below expected performance to expected performance. Conclusions: Using a randomized, placebo-controlled crossover design, we demonstrated improvement in processing speed and working memory with a nocturnal blue light blocking intervention among individuals with insomnia symptoms. ( JINS, 2019, 25, 668–677)

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Automatic sleep/wake identification from wrist activity.

Roger Cole, Daniel F. Kripke, William Gruen … (1992)

The purpose of this study was to develop and validate automatic scoring methods to distinguish sleep from wakefulness based on wrist activity. Forty-one subjects (18 normals and 23 with sleep or psychiatric disorders) wore a wrist actigraph during overnight polysomnography. In a randomly selected subsample of 20 subjects, candidate sleep/wake prediction algorithms were iteratively optimized against standard sleep/wake scores. The optimal algorithms obtained for various data collection epoch lengths were then prospectively tested on the remaining 21 subjects. The final algorithms correctly distinguished sleep from wakefulness approximately 88% of the time. Actigraphic sleep percentage and sleep latency estimates correlated 0.82 and 0.90, respectively, with corresponding parameters scored from the polysomnogram (p < 0.0001). Automatic scoring of wrist activity provides valuable information about sleep and wakefulness that could be useful in both clinical and research applications.

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A cognitive model of insomnia.

A.G. Harvey (2002)

Insomnia is one of the most prevalent psychological disorders, causing sufferers severe distress as well as social, interpersonal, and occupational impairment. Drawing on well-validated cognitive models of the anxiety disorders as well as on theoretical and empirical work highlighting the contribution of cognitive processes to insomnia, this paper presents a new cognitive model of the maintenance of insomnia. It is suggested that individuals who suffer from insomnia tend to be overly worried about their sleep and about the daytime consequences of not getting enough sleep. This excessive negatively toned cognitive activity triggers both autonomic arousal and emotional distress. It is proposed that this anxious state triggers selective attention towards and monitoring of internal and external sleep-related threat cues. Together, the anxious state and the attentional processes triggered by it tricks the individual into overestimating the extent of the perceived deficit in sleep and daytime performance. It is suggested that the excessive negatively toned cognitive activity will be fuelled if a sleep-related threat is detected or a deficit perceived. Counterproductive safety behaviours (including thought control, imagery control, emotional inhibition, and difficulty problem solving) and erroneous beliefs about sleep and the benefits of worry are highlighted as exacerbating factors. The unfortunate consequence of this sequence of events is that the excessive and escalating anxiety may culminate in a real deficit in sleep and daytime functioning. The literature providing preliminary support for the model is reviewed and the clinical implications and limitations discussed.

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Evening exposure to a light-emitting diodes (LED)-backlit computer screen affects circadian physiology and cognitive performance.

Christian Cajochen, Sylvia Frey, Doreen Anders … (2011)

Many people spend an increasing amount of time in front of computer screens equipped with light-emitting diodes (LED) with a short wavelength (blue range). Thus we investigated the repercussions on melatonin (a marker of the circadian clock), alertness, and cognitive performance levels in 13 young male volunteers under controlled laboratory conditions in a balanced crossover design. A 5-h evening exposure to a white LED-backlit screen with more than twice as much 464 nm light emission {irradiance of 0,241 Watt/(steradian × m(2)) [W/(sr × m(2))], 2.1 × 10(13) photons/(cm(2) × s), in the wavelength range of 454 and 474 nm} than a white non-LED-backlit screen [irradiance of 0,099 W/(sr × m(2)), 0.7 × 10(13) photons/(cm(2) × s), in the wavelength range of 454 and 474 nm] elicited a significant suppression of the evening rise in endogenous melatonin and subjective as well as objective sleepiness, as indexed by a reduced incidence of slow eye movements and EEG low-frequency activity (1-7 Hz) in frontal brain regions. Concomitantly, sustained attention, as determined by the GO/NOGO task; working memory/attention, as assessed by "explicit timing"; and declarative memory performance in a word-learning paradigm were significantly enhanced in the LED-backlit screen compared with the non-LED condition. Screen quality and visual comfort were rated the same in both screen conditions, whereas the non-LED screen tended to be considered brighter. Our data indicate that the spectral profile of light emitted by computer screens impacts on circadian physiology, alertness, and cognitive performance levels. The challenge will be to design a computer screen with a spectral profile that can be individually programmed to add timed, essential light information to the circadian system in humans.