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.

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We examined whether dynamic light across a scheduled 16-h waking day influences cognitive performance, visual comfort, melatonin secretion, sleepiness and sleep under strictly controlled laboratory conditions of 49-h duration.Participants spent the first 5-h in the evening under standard lighting, followed by an 8-h nocturnal sleep episode at habitual bedtimes. Thereafter volunteers either woke up with static daylight LED (100 lux and 4000 Kelvin) or with a dynamic daylight LED that changed color (2700 -5000 Kelvin) and intensity (0 -100 lux) across the scheduled 16-h waking day. This was followed by an 8-h nocturnal treatment sleep episode at habitual bedtimes. Thereafter, volunteers spent another 12-h either under static or dynamic light during scheduled wakefulness.Under dynamic light, evening melatonin levels were less suppressed 1.5hours prior to usual bedtime, and participants felt less vigilant in the evening compared to static light. Sleep latency was significantly shorter in both the baseline and treatment night compared to the static light condition while sleep structure, sleep quality, cognitive performance and visual comfort did not significantly change. Our results support the recommendation of using blue-depleted light and low illuminances in the late evening, which can be achieved by a dynamically changing daylight LED solution.

Background: Adolescents frequently consume caffeine with unknown consequences on sleep and circadian rhythms. In adults, the evidence indicates that caffeine acutely reduces homeostatic sleep pressure and delays the circadian timing system.Objective: Here, we investigated the acute effects of caffeine intake on the developing sleep-wake regulatory system of teenagers.Design: In a double-blind randomized crossover laboratory study, 18 teenagers (16.1 ± 1 years old, pubertal development scale [PDS]: 2.76 ± 0.35) ingested 80 mg caffeine (vs placebo) four hours prior to bedtime. Until bedtime, participants regularly filled in the Karolinska Sleepiness Scale and gave saliva samples to measure melatonin secretion. During nighttime, we quantified homeostatic sleep need by the electroencephalographically derived amount of slow wave sleep duration (SWS). After sleep, participants rated sleep quality by the Leeds Sleep Evaluation Questionnaire.Results: While participants felt less sleepy after caffeine vs. placebo (P=0.038), their ratings of sleep quality were not strongly affected by the treatment. However, objectively, SWS was on average reduced by ~20 min after caffeine vs. placebo (P=0.026). This caffeine-induced reduction was more pronounced in those individuals with more SWS under placebo (regression: P=0.042; standardized beta=0.622, P=0.011), even if controlling for habitual caffeine intake or pubertal stage (PDS). In melatonin onsets we observed both delays and advances in response to caffeine. This variance could partly be explained by differences in relative dose (i.e., mg caffeine/kg of bodyweight): the higher the relative dose, the more likely were delays (regression: P=0.01; standardized beta=0.592, P=0.01).Conclusions: In teenagers, evening caffeine intake of already 80 mg (i.e. ~8fl oz of common energy drinks) is sufficient to promote alertness at the costs of subsequent sleep. These costs might be more pronounced in adolescents with a higher need for SWS. Moreover, caffeine might disturb the circadian timing system, consequently hampering the balanced interplay of sleep-wake regulatory components.

Background Polysomnography (PSG) is the gold standard for the diagnosis of obstructive sleep apnoea (OSA). Home sleep apnoea testing with peripheral arterial tonometry (PAT) is a recommended diagnostic alternative for patients with an increased risk for OSA. In a large clinical cohort, we investigated concordance and predictors for discordance in diagnosing OSA using PAT and PSG, and three-year cardiovascular risk in patients with discordant OSA diagnosis. Methods Retrospective monocentric cohort study. Patients with a PAT AHI ≥ 5/h followed by an in-hospital PSG within three months were included. All patients with a PAT AHI ≥ 5/h but a PSG AHI < 5/h were classified as discordant. Patients with PAT and PSG AHI ≥ 5/h were classified as concordant. To ascertain cardiovascular risk, major adverse cardiovascular events (MACE) were analyzed in discordant patients and sex, age, body mass index (BMI) and cardiovascular disease-matched concordant patients over a follow-up time of 3.1 ± 0.06 years. Results A total of 940 patients, 66% male with an average age of 55 ± 0.4 years and BMI of 31 ± 0.2 kg/m2 were included. Agreement in OSA diagnosis was observed in 80% of patients (55% in mild and 86% in moderate and severe OSA). Factors significantly associated with a discordant diagnosis were female sex, younger age and lower BMI, but not comorbidities. There was no significant difference in MACE (p = 0.920) between discordant patients (n = 155) and matched concordant patients (n = 274) with or without therapy. Conclusions Concordance between PAT and PSG diagnosis of sleep apnoea is good, particularly in moderate and severe OSA. Predictors for discordant results between PAT and PSG were age, sex and BMI. MACE risk is similar in those with OSA diagnosed by PAT or PSG.