LED *Shared senior authors. light sources have a discontinuous light spectrum with a prominent ‘blue’ peak between 450 and 470 nm that influences non-image forming responses in humans. We tested an LED lighting solution mimicking a daylight spectrum on visual comfort, circadian physiology, daytime alertness, mood, cognitive performance and sleep. Fifteen young males twice spent 49 hours in the laboratory under a conventional-LED and under a daylight-LED condition in a balanced cross over design flanked by a baseline and a post-light exposure night. Despite different light spectra, the photopic lux and the correlated colour temperature of the lighting were the same for both LEDs. The colour rendering index and the melanopic strength were 25.3% and 21%, respectively, higher for the daylight LED than the conventional LED. The volunteers had better visual comfort, felt more alert and happier in the morning and evening under daylight LED than conventional LED, while the diurnal melatonin profile, psychomotor vigilance and working memory performance were not significantly different. Delta EEG activity (0.75–4.5 Hz) was significantly higher after daylight-LED than conventional-LED exposure during the post-light exposure night. We have evidence that a daylight-LED solution has beneficial effects on visual comfort, daytime alertness, mood and sleep intensity in healthy volunteers.

Although traumatic events are presumed to cause sleep disturbances, particularly insomnia, sleep in populations subjected to forced displacement has received little attention. The present study examined the prevalence of insomnia and associated factors in internally displaced persons (IDPs) from Abkhazia 15 years after displacement to Tbilisi. Detailed subjective information about sleep-wake habits, sleep-related and stress-related parameters were obtained from 87 IDPs categorized into good sleepers and insomniacs. The Insomnia Severity Index, Perceived Stress Scale and Beck Depression Inventory were administered. The incidence of insomnia was 41.4%. The majority of insomniacs strongly believed that war-related stress accounted for the onset of their insomnia. Stepwise regression (95% confidence interval) revealed four variables significantly associated with insomnia status: self-estimated influence of war related stress (odds ratio (OR) = 2.51), frequency of nightmares (OR = 1.6), Perceived Stress Scale score (OR = 1.14) and Beck Depression Inventory score (OR = 1.12). Insomnia in IDPs was strongly related to war-associated remembered stress. ‛Over thinking' about major stress exposure enhanced IDPs' vulnerability to insomnia. These findings have implications for the management of insomnia and associated impairment of daytime functioning in IDPs.

The extent to which sleep disorders are associated with impairment of health-related quality of life (HRQoL) is poorly described in the developing world. We investigated the prevalence and severity of various sleep disorders and their associations with HRQoL in an urban Georgian population. 395 volunteers (20–60 years) completed Pittsburgh Sleep Quality Index, Epworth Sleepiness Scale, STOP-Bang questionnaire, Insomnia Severity Index, Beck Depression Inventory-Short Form, and Short Form Health Survey (SF-12). Socio-demographic data and body mass index (BMI) were obtained. The prevalence of sleep disorders and their association with HRQoL was considerable. All SF-12 components and physical and mental component summaries (PCS, MCS) were significantly lower in poor sleepers, subjects with daytime sleepiness, apnea risk, or insomnia. Insomnia and apnea severity were also associated with lower scores on most SF-12 dimensions. The effect of insomnia severity was more pronounced on MCS, while apnea severity—on PCS. Hierarchical analyses showed that after controlling for potential confounding factors (demographics, depression, BMI), sleep quality significantly increased model’s predictive power with an R2 change (ΔR2) by 3.5% for PCS (adjusted R2 = 0.27) and by 2.9% for MCS (adjusted R2 = 0.48); for the other SF-12 components ΔR2 ranged between 1.4% and 4.6%. ESS, STOP-Bang, ISI scores, all exerted clear effects on PCS and MCS in an individual regression models. Our results confirm and extend the findings of studies from Western societies and strongly support the importance of sleep for HRQoL. Elaboration of intervention programs designed to strengthen sleep-related health care and thereof HRQoL is especially important in the developing world.

We examined whether dynamically changing light across a scheduled 16-h waking day influences sleepiness, cognitive performance, visual comfort, melatonin secretion, and sleep under controlled laboratory conditions in healthy men. Fourteen participants underwent a 49-h laboratory protocol in a repeated-measures study design. They spent the first 5 hours in the evening under standard lighting, followed by an 8-h nocturnal sleep episode at habitual bedtimes. Thereafter, volunteers either woke up to static light or to a dynamic light that changed spectrum and intensity across the scheduled 16-h waking day. Following an 8-h nocturnal sleep episode, the volunteers spent another 11 hours either under static or dynamic light. Static light attenuated the evening rise in melatonin levels more compared to dynamic light as indexed by a significant reduction in the melatonin AUC prior to bedtime during static light only. Participants felt less vigilant in the evening during dynamic light. After dynamic light, sleep latency was significantly shorter in both the baseline and treatment night while sleep structure, sleep quality, cognitive performance, and visual comfort did not significantly differ. The study shows that dynamic changes in spectrum and intensity of light promote melatonin secretion and sleep initiation in healthy men.