In the last three decades the two-process model of sleep regulation has served as a major conceptual framework in sleep research. It has been applied widely in studies on fatigue and performance and to dissect individual differences in sleep regulation. The model posits that a homeostatic process (Process S) interacts with a process controlled by the circadian pacemaker (Process C), with time-courses derived from physiological and behavioural variables. The model simulates successfully the timing and intensity of sleep in diverse experimental protocols. Electrophysiological recordings from the suprachiasmatic nuclei (SCN) suggest that S and C interact continuously. Oscillators outside the SCN that are linked to energy metabolism are evident in SCN-lesioned arrhythmic animals subjected to restricted feeding or methamphetamine administration, as well as in human subjects during internal desynchronization. In intact animals these peripheral oscillators may dissociate from the central pacemaker rhythm. A sleep/fast and wake/feed phase segregate antagonistic anabolic and catabolic metabolic processes in peripheral tissues. A deficiency of Process S was proposed to account for both depressive sleep disturbances and the antidepressant effect of sleep deprivation. The model supported the development of novel non-pharmacological treatment paradigms in psychiatry, based on manipulating circadian phase, sleep and light exposure. In conclusion, the model remains conceptually useful for promoting the integration of sleep and circadian rhythm research. Sleep appears to have not only a short-term, use-dependent function; it also serves to enforce rest and fasting, thereby supporting the optimization of metabolic processes at the appropriate phase of the 24-h cycle. © 2016 European Sleep Research Society.

This research examined the impact of daylight exposure on the health of office workers from the perspective of subjective well-being and sleep quality as well as actigraphy measures of light exposure, activity, and sleep-wake patterns.Participants (N = 49) included 27 workers working in windowless environments and 22 comparable workers in workplaces with significantly more daylight. Windowless environment is defined as one without any windows or one where workstations were far away from windows and without any exposure to daylight. Well-being of the office workers was measured by Short Form-36 (SF-36), while sleep quality was measured by Pittsburgh Sleep Quality Index (PSQI). In addition, a subset of participants (N = 21; 10 workers in windowless environments and 11 workers in workplaces with windows) had actigraphy recordings to measure light exposure, activity, and sleep-wake patterns.Workers in windowless environments reported poorer scores than their counterparts on two SF-36 dimensions--role limitation due to physical problems and vitality--as well as poorer overall sleep quality from the global PSQI score and the sleep disturbances component of the PSQI. Compared to the group without windows, workers with windows at the workplace had more light exposure during the workweek, a trend toward more physical activity, and longer sleep duration as measured by actigraphy.We suggest that architectural design of office environments should place more emphasis on sufficient daylight exposure of the workers in order to promote office workers' health and well-being.

The review addresses the development of a new solid-state lighting system for the International Space Station (ISS) that is intended to enhance the illumination of the working and living environment of astronauts and to improve sleep, circadian entrainment, and daytime alertness.Spaceflight missions often expose astronauts and mission support ground crews to atypical sleep-wake cycles and work schedules. A recent, extensive study describes the sleep characteristics and use of sleep-promoting pharmaceuticals in astronauts before, during, and after spaceflight. The acceptability, feasibility, and efficacy of the new ISS solid-state lighting systems are currently being tested in ground-based, analog studies. Installation of this lighting system on the ISS is scheduled to begin later this year. In-flight testing of this lighting system is planned to take place during ISS spaceflight expeditions.If the new ISS lighting system is capable of improving circadian entrainment and sleep during spaceflight, it should enhance astronaut health, performance, well-being, and safety. Such an advance would open the door to future lighting applications for humans living on Earth.

This article focuses on melatonin and other melatonin receptor agonists, and specifically their circadian phase shifting and sleep-enhancing properties. The circadian system and circadian rhythm sleep-wake disorders are briefly reviewed, followed by a summary of the circadian phase shifting, sleep-enhancing properties, and possible safety concerns associated with melatonin and other melatonin receptor agonists. The recommended use of melatonin, including dose and timing, in the latest American Academy of Sleep Medicine Clinical Practice Guidelines for the treatment of intrinsic circadian rhythm disorders is also reviewed. Lastly, the practical aspects of treatment and consideration of clinical treatment outcomes are discussed.Copyright © 2020 Elsevier Inc. All rights reserved.

To assess the relationship between habitual sleep disturbances and the incidence of type 2 diabetes and to obtain an estimate of the risk.We conducted a systematic search of publications using MEDLINE (1955-April 2009), EMBASE, and the Cochrane Library and manual searches without language restrictions. We included studies if they were prospective with follow-up >3 years and had an assessment of sleep disturbances at baseline and incidence of type 2 diabetes. We recorded several characteristics for each study. We extracted quantity and quality of sleep, how they were assessed, and incident cases defined with different validated methods. We extracted relative risks (RRs) and 95% CI and pooled them using random-effects models. We performed sensitivity analysis and assessed heterogeneity and publication bias.We included 10 studies (13 independent cohort samples; 107,756 male and female participants, follow-up range 4.2-32 years, and 3,586 incident cases of type 2 diabetes). In pooled analyses, quantity and quality of sleep predicted the risk of development of type 2 diabetes. For short duration of sleep (< or =5-6 h/night), the RR was 1.28 (95% CI 1.03-1.60, P = 0.024, heterogeneity P = 0.015); for long duration of sleep (>8-9 h/night), the RR was 1.48 (1.13-1.96, P = 0.005); for difficulty in initiating sleep, the RR was 1.57 (1.25-1.97, P < 0.0001); and for difficulty in maintaining sleep, the RR was 1.84 (1.39-2.43, P < 0.0001).Quantity and quality of sleep consistently and significantly predict the risk of the development of type 2 diabetes. The mechanisms underlying this relation may differ between short and long sleepers.

The aim of this work was to study the effects of bright light-induced circadian phase shifts on sleep propensity and sleep architecture while the timing of the sleep/wake cycle is kept constant. Twenty-three normal subjects underwent an 11-day study including: (i) baseline sleep and vigilance evaluation; (ii) baseline evaluation of the circadian temperature rhythm with a 40-h constant routine; (iii) five hours of bright light exposure on each of three days; (iv) post-treatment sleep and vigilance evaluation; (v) post-treatment circadian rhythm evaluation with a second 40-h constant routine. Subjects were divided into three groups: eight subjects were exposed to bright light in the morning ('Morning group'), eight subjects were exposed in the evening ('Evening group'), and seven subjects were exposed in the afternoon ('Afternoon group'). After light exposure, the Morning group showed an advance of 1.23 h in the phase of the temperature rhythm, the Evening group showed a delay of 1.62 h, and the Afternoon group showed a non-significant advance of 0.5 h. In support of expectations, early-night sleep propensity was decreased by evening bright light, was increased in almost all subjects exposed to morning bright light, and was not changed by afternoon bright light exposure. The phase shift created by bright light exposure did not seem to be large enough to have a systematic effect on sleep consolidation or on REM sleep parameters in any of the three groups, suggesting that these variables are less sensitive to alterations in phase of the circadian oscillator than early-night sleep propensity.

Artificial light endows a "round-the-clock", 24-h/7-d society. Chronic exposure to light at night contributes to health hazards for humans, including disorders of sleep. Yet the influence of inter-individual traits, such as sex-differences, on light sensitivity remains to be established. Here we investigated potential sex-differences to evening light exposure of 40 lx at 6500 K (blue-enriched) or at 2500 K (non-blue-enriched), and their impact on brightness perception, vigilant attention and sleep physiology. In contrast to women, men had higher brightness perception and faster reaction times in a sustained attention task during blue-enriched light than non-blue-enriched. After blue-enriched light exposure, men had significantly higher all-night frontal NREM sleep slow-wave activity (SWA: 2-4 Hz), than women, particularly during the beginning of the sleep episode. Furthermore, brightness perception during blue-enriched light significantly predicted men's improved sustained attention performance and increased frontal NREM SWA. Our data indicate that, in contrast to women, men show a stronger response to blue-enriched light in the late evening even at very low light levels (40lux), as indexed by increased vigilant attention and sleep EEG hallmarks. Collectively, the data indicate that sex differences in light sensitivity might play a key role for ensuring the success of individually-targeted light interventions.

Light exposure, particularly at the short-wavelength range, triggers several nonvisual responses in humans. However, the extent to which the melatonin-suppressing and alerting effect of light differs among individuals remains unknown.

Artificial lighting has been beneficial to society, but unnecessary light exposure at night may cause various health problems. We aimed to investigate how whole-night bedside light can affect sleep quality and brain activity.Ten healthy sleepers underwent two polysomnography (PSG) sessions, one with the lights off and one with the lights on. PSG variables related to sleep quality were extracted and compared between lights-off and lights-on sleep. Spectral analysis was performed to rapid eye movement (REM) sleep and non-REM (NREM) sleep epochs to reveal any light-induced differences in background brain rhythms.Lights-on sleep was associated with increased stage 1 sleep (N1), decreased slow-wave sleep (SWS), and increased arousal index. Spectral analysis revealed that theta power (4-8Hz) during REM sleep and slow oscillation (0.5-1Hz), delta (1-4Hz), and spindle (10-16Hz) power during NREM sleep were decreased in lights-on sleep conditions.Sleeping with the light on not only causes shallow sleep and frequent arousals but also has a persistent effect on brain oscillations, especially those implicated in sleep depth and stability. Our study demonstrates additional hazardous effect of light pollution on health.Copyright © 2013 Elsevier B.V. All rights reserved.

环境光照作为重要的授时因子, 对多种生理和心理功能存在广泛影响, 其对情绪的非视觉作用尤其引起研究者们的关注。研究发现, 环境光照的照度、色温和波长均是影响情绪的重要物理因素; 短光周期、夜间人工光以及持续光照/黑暗等异常光照模式则会导致情绪障碍; 光照的情绪效应还受到光照时长、时间点、个体特征、主观偏好及基因类型等的调节。光照作用于情绪的路径主要包括两个方面, 一方面视网膜中的内在光敏感神经节细胞将光信号投射至情绪调节相关脑区直接影响情绪; 另一方面光信号通过同步内部生理节律及其调节下的激素分泌、神经传递和睡眠间接影响情绪。未来研究考察短时光照的视觉功效时需要采用更客观多样化的情绪测量技术, 综合非视觉与视觉作用路径深入对比健康与情绪障碍群体的差异性。

自人类视网膜上发现存在新型的内在光敏感神经节细胞以来, 环境光照对个体生理心理功能的非视觉作用备受研究者青睐, 其中环境光照对认知功能的非视觉作用结果并不十分一致且内在机理尚不明确。环境光照的认知功效会受到光学参数、光照模式、时间因素、个体差异以及任务特征等的共同调节。未来的研究需要从环境光对心理认知功能的作用模式, 动态办公照明系统的开发, 面向特殊群体的个性化照明以及光照非视觉作用产生的分子生物学机制等视角进行扩展和深化。

Background: Seasonal variations in physiology and behavior have frequently been reported. Light is the major zeitgeber for synchronizing internal circadian rhythms with the external solar day. Non-image forming effects of light radiation, for example, phase resetting of the circadian rhythms, melatonin suppression, and acute alerting effects, depend on several characteristics of the light exposure including intensity, timing and duration, spectral composition and previous light exposure, or light history. The aim of the present study was to report on the natural pattern of diurnal and seasonal light exposure and to examine seasonal variations in the circadian change of melatonin and cortisol concentrations for a group of Swedish office workers. Methods: Fifteen subjects participated in a field study that was carried out in the south of Sweden. Ambulatory equipment was used for monthly measurements of the daily exposure to light radiation across the year. The measurements included illuminance and irradiance. The subjects collected saliva samples every 4 h during 1 day of the monthly measuring period. Results: The results showed that there were large seasonal differences in daily amount of light exposure across the year. Seasonal differences were observed during the time periods 04: 00-08: 00, 08: 00-12: 00, 12: 00-16: 00, 16: 00-20: 00, and 20: 00-24: 00. Moreover, there were seasonal differences regarding the exposure pattern. The subjects were to a larger extent exposed to light in the afternoon/evening in the summer. During the winter, spring, and autumn, the subjects received much of the daily light exposure in the morning and early afternoon. Regarding melatonin, a seasonal variation was observed with a larger peak level during the winter and higher levels in the morning at 07: 00. Conclusions: This study adds to the results from other naturalistic studies by reporting on the diurnal and seasonal light exposure patterns for a group living at a northern latitude of 56 degrees N, with large annual variations in photoperiod length. It seems to be seasonal variation in the lighting conditions, both concerning intensities as well as regarding the pattern of the light exposure to which people living at high latitudes are exposed which may result in seasonal variation in the circadian profile of melatonin.

Previous work has demonstrated that exposure to an hour of bright light in the morning and the evening during the Polar winter has beneficial effects on circadian phase. This study investigated the effect of a single hour of bright white morning light on circadian phase, sleep, alertness and cognitive performance. Nine individuals (eight male, one female, median age 30 years), wintering at Halley Research Station (75°S), Antarctica from 7th May until 6th August 2007, were exposed to bright white light for a fortnight from 08:30 to 09:30 h, with two fortnight control periods on either side. This sequence was performed twice, before and following Midwinter. Light exposure, sleep and alertness were assessed daily by actigraphy, sleep diaries and subjective visual analogue scales. Circadian phase (assessed by urinary 6-sulphatoxymelatonin rhythm) and cognitive performance were evaluated at the end of each fortnight. During light exposure circadian phase was advanced from 4.97 ± 0.96 decimal hours (dh) (mean ± SD) to 4.08 ± 0.68 dh (p = 0.003). Wake-up time was shifted by a similar margin from 8.45 ± 1.83 dh to 7.59 ± 0.78 dh (p < 0.001). Sleep start time was also advanced (p = 0.047) but by a lesser amount, consequently, actual sleep time was slightly reduced. There was no change in objective or subjective measures of sleep quality or subjective measures of alertness. An improvement in cognitive performance was found with both the Single Letter Cancellation Test (p < 0.001) and the Digit Symbol Substitution Test (p = 0.026) with preserved circadian variation. These beneficial effects of a single short duration light treatment may have implications not only for the Antarctic but other remote environments where access to natural light and delayed circadian phase, is problematic. These results require validation in larger studies at varying locations.Copyright © 2012 Elsevier Ireland Ltd. All rights reserved.

To assess light exposure during days with indoor, outdoor, and night work and days off work.Light intensity was continuously recorded for 7 days across the year among indoor (n = 170), outdoor (n = 151), and night workers (n = 188) in Denmark (55-56°N) equipped with a personal light recorder. White light intensity, duration above 80, 1000, and 2500 lux, and proportion of red, green, and blue light was depicted by time of the day and season for work days and days off work.Indoor workers' average light exposure only intermittently exceeded 1000 lux during daytime working hours in summer and never in winter. During daytime working hours, most outdoor workers exceeded 2500 lux in summer and 1000 lux in winter. Night workers spent on average 10-50 min >80 lux when working night shifts. During days off work, indoor and night workers were exposed to higher light intensities than during work days and few differences were seen between indoor, outdoor, and night workers. The spectral composition of light was similar for indoor, outdoor, and night workers during days at and off work.The night workers of this study were during night hours on average exposed for a limited time to light intensities expected to suppress melatonin. The indoor workers were exposed to light levels during daylight hours that may reduce general well-being and mood, especially in winter. Outdoor workers were during summer daylight hours exposed to light levels comparable to those used for the treatment of depression.© The Author(s) 2019. Published by Oxford University Press on behalf of the British Occupational Hygiene Society.

Light is considered the dominant environmental cue, or zeitgeber, influencing the sleep-wake cycle. Despite recognizing the importance of light for our well-being, less is known about the specific conditions under which light is optimally associated with better sleep. Therefore, a systematic review was conducted to examine the association between the amount and timing of light exposure in relation to sleep outcomes in healthy, community-dwelling adults. A systematic search was conducted of four databases from database inception to June 2016. In total, 45 studies met the review eligibility criteria with generally high study quality excepting for the specification of eligibility criteria and the justification of sample size. The majority of studies involved experimental manipulation of light (n = 32) vs observational designs (n = 13). Broad trends emerged suggesting that (1) bright light (>1000 lux) has positive implications for objectively assessed sleep outcomes compared to dim (<100 lux) and moderate light (100-1000 lux) and (2) bright light (>1000 lux) has positive implications for subjectively assessed sleep outcomes compared to moderate light (100-1000 lux). Effects due to the amount of light are moderated by the timing of light exposure such that, for objectively assessed sleep outcomes, brighter morning and evening light exposure are consistent with a shift in the timing of the sleep period to earlier and later in the day, respectively. For subjectively assessed sleep outcomes, brighter light delivered in the morning was associated with self-reported sleep improvements and brighter evening light exposure was associated with worse self-reported sleep.Copyright © 2018 National Sleep Foundation. All rights reserved.

In 8 subjects the spontaneous termination of sleep was determined after repetitive exposure to either bright or dim light, between 6.00 and 9.00 h, on 3 days preceding sleep assessment. Sleep duration was significantly shorter following bright light than following dim light. During sleep the time course of EEG energy was not affected by the light treatment. Analysis of the time course of body temperature during sleep indicated an earlier rise of body temperature following the bright light treatment. In terms of the two-process model of sleep regulation this can be interpreted as a direct effect of light on the circadian phase of the wake up threshold.

Disturbances in rest-activity rhythm are prominent and disabling symptoms in Alzheimer's disease (AD). Nighttime sleep is severely fragmented and daytime activity is disrupted by multiple napping episodes. In most institutional environments, light levels are very low and may not be sufficient to enable the circadian clock to entrain to the 24-hour day. The purpose of this randomized, placebo-controlled, clinical trial was to test the effectiveness of morning bright light therapy in reducing rest-activity (circadian) disruption in institutionalized patients with severe AD.Subjects (n = 46, mean age 84 years) meeting the NINCDS-ADRDA (National Institute of Neurological and Communicative Disorders and Stroke--the Alzheimer's Disease and Related Disorders Association) AD diagnostic criteria were recruited from two large, skilled nursing facilities in San Francisco, California. The experimental group received one hour (09:30-10:30) of bright light exposure (> or = 2500 lux in gaze direction) Monday through Friday for 10 weeks. The control group received usual indoor light (150-200 lux). Nighttime sleep efficiency, sleep time, wake time and number of awakenings and daytime wake time were assessed using actigraphy. Circadian rhythm parameters were also determined from the actigraphic data using cosinor analysis and nonparametric techniques. Repeated measures analysis of variance (ANOVA) was used to test the primary study hypotheses.Although significant improvements were found in subjects with aberrant timing of their rest-activity rhythm, morning bright light exposure did not induce an overall improvement in measures of sleep or the rest-activity in all treated as compared to control subjects. The results indicate that only subjects with the most impaired rest-activity rhythm respond significantly and positively to a brief (one hour) light intervention.

Moderate circadian phase shifts were induced by 3 days of bright light exposure, without changing the habitual sleep schedule. Daytime sleep propensity was evaluated with multiple sleep latency tests (MSLT) conducted before and after the light treatment. Phase shifts were estimated using the core body temperature rhythm recorded during constant routines. The subjects were divided into three groups according to the timing of the bright light exposure. Morning bright light exposure (Morning group) advanced the circadian phase by about 1.2 hours, evening bright light (Evening group) delayed the circadian phase by 1.6 hours on average; whereas, bright light administered in the afternoon (Afternoon group) did not change the circadian phase. After the light treatment, daytime sleep latencies decreased in the Evening and Afternoon groups, but did not change in the Morning group. Reduced sleep latencies in the Afternoon group probably reflect an increase in the manifest sleep tendency induced by the protocol itself. It is suggested that, in the presence of a high physiological sleep tendency, a moderate circadian phase delay may increase further daytime sleep propensity, whereas a moderate circadian phase advance may help to maintain daytime sleep propensity at a lower level.

Genetic analyses of circadian rhythm sleep disorders (CRSD), such as familial advanced sleep phase syndrome (ASPS) and delayed sleep phase syndrome (DSPS), and morningness-eveningness revealed the relationship between variations in clock genes and diurnal change in human behaviors. Variations such as T3111C in the Clock gene are reportedly associated with morningness-eveningness. Two of the pedigrees of familial ASPS (FASPS) are caused by mutations in clock genes: the S662G mutation in the Per2 gene or the T44A mutation in the casein kinase 1 delta (CK1delta) gene, although these mutations are not found in other pedigrees of FASPS. As for DSPS, a missense variation in the Per3 gene is identified as a risk factor, while the one in the CK1epsilon gene is thought to be protective. These findings suggest that further, as yet unidentified, gene variations are involved in human circadian activity. Many of the CRSD-relevant variations reported to date seem to affect the phosphorylation status of the clock proteins. A recent study using mathematical models of circadian rhythm generation has provided a new insight into the role of phosphorylation in the molecular mechanisms of these disorders.

By affecting the internal timing mechanisms of the brain, light regulates human physiology and behavior, perhaps most notably the sleep-wake cycle. Humans spend over 90% of their waking hours indoors, yet light in the built environment is not designed to affect circadian rhythms.Using a device calibrated to measure light that is effective for the circadian system (circadian-effective light), collect personal light exposures in office workers and relate them to their sleep and mood.The research was conducted in 5 buildings managed by the US General Services Administration.This study recruited 109 participants (69 females), of whom 81 (54 females) participated in both winter and summer.Self-reported measures of mood and sleep, and objective measures of circadian-effective light and activity rhythms were collected for 7 consecutive days.Compared to office workers receiving low levels of circadian-effective light in the morning, receiving high levels in the morning is associated with reduced sleep onset latency (especially in winter), increased phasor magnitudes (a measure of circadian entrainment), and increased sleep quality. High levels of circadian-effective light during the entire day are also associated with increased phasor magnitudes, reduced depression, and increased sleep quality.The present study is the first to measure personal light exposures in office workers using a calibrated device that measures circadian-effective light and relate those light measures to mood, stress, and sleep. The study's results underscore the importance of daytime light exposures for sleep health.Copyright © 2017 National Sleep Foundation. All rights reserved.

Chronic sleep restriction (SR) has deleterious effects on cognitive performance that can be counteracted by light exposure. However, it is still unknown if naturalistic light settings (dawn simulating light) can enhance daytime cognitive performance in a sustainable matter. Seventeen participants were enrolled in a 24-h balanced cross-over study, subsequent to SR (6-h of sleep). Two different light settings were administered each morning: a) dawn simulating light (DsL; polychromatic light gradually increasing from 0 to 250 lx during 30 min before wake-up time, with light around 250 lx for 20 min after wake-up time) and b) control dim light (DL; <8 lx). Cognitive tests were performed every 2 h during scheduled wakefulness and questionnaires were completed hourly to assess subjective mood. The analyses yielded a main effect of "light condition" for the motor tracking task, sustained attention to response task and a working memory task (visual 1 and 3-back task), as well as for the Simple Reaction Time Task, such that participants showed better task performance throughout the day after morning DsL exposure compared to DL. Furthermore, low performers benefited more from the light effects compared to high performers. Conversely, no significant influences from the DsL were found for the Psychomotor Vigilance Task and a contrary effect was observed for the digit symbol substitution test. No light effects were observed for subjective perception of sleepiness, mental effort, concentration and motivation. Our data indicate that short exposure to artificial morning light may significantly enhance cognitive performance in a domain-specific manner under conditions of mild SR.Copyright © 2014 Elsevier B.V. All rights reserved.

The aim of the present study is to examine the relationship between light and sleep, in adolescents with an evening circadian preference.For a period of seven days, ninety-nine adolescents wore a wrist actigraph to assess light exposure and objective sleep and completed a sleep diary to assess subjective sleep.Lower average light intensity across the preceding 24 h was associated with a later sleep onset (p < 0.01) and a later next-day sleep offset (p < 0.05). A later time of last exposure to more than 10 lux was associated with a later sleep onset (p < 0.001) and a shorter objective total sleep time (p < 0.001), as well as a later bedtime (p < 0.001) and a shorter subjective total sleep time (p < 0.001). Furthermore, exploratory analyses found that lower average early morning light exposure (between 4 and 9 AM) was associated with later sleep onset (p < 0.05), a later next-day sleep offset (p < 0.05), and a later next-day waketime (p < 0.01), lower average afternoon light exposure (between 2 and 7 PM) was associated with a later next-day sleep offset (p < 0.05), and lower average evening light exposure (between 7 PM and 12 AM) was associated with longer subjective total sleep time (p < 0.01).This study highlights the importance of light exposure, particularly the timing of light exposure, for establishing healthy patterns of sleep among adolescents with a propensity for a delayed bedtime and waketime. These findings provide additional evidence for targeting light exposure when designing interventions to improve adolescent sleep.Copyright © 2020 Elsevier B.V. All rights reserved.

Sleep disturbances are common non-motor symptoms of Parkinson's disease (PD). We aimed to compare the safety and efficacy of trazodone with melatonin and clonazepam in patients with PD and sleep complaints.This single-center, double-blind, randomized clinical trial was conducted on PD patients with subjective sleep complaints. Eligible patients were randomized 1:1:1 to receive melatonin 3 mg/day, clonazepam 1 mg/day, or trazodone 50 mg/day for 4 weeks. The primary outcome measure was the changes in Pittsburgh Sleep Quality Index (PSQI) scores. The mean change in Epworth Sleepiness Scale (ESS) and RBD screening questionnaire (RBDSQ) was considered as the secondary outcome measures.A total of 112 eligible patients were randomized and 93 participants, melatonin (n = 31), trazodone (n = 31), and clonazepam (n = 31), completed the study. There was a significant decrease in PSQI scores after 4 weeks of treatment in all groups. The mean changes of PSQI from baseline were similar among the treatment arms (P = 0.325). Mean changes of RBDSQ and ESS from baseline were significantly different between study arms (P < 0.05). Melatonin intake was associated with a higher decrease in RBDSQ score compared to trazodone (P = 0.011) and clonazepam (P = 0.004). Trazodone intake was associated with a higher decrease in ESS score compared to clonazepam (P = 0.010). Mild adverse events were reported in three patients in the clonazepam, two patients in the trazodone group, and none in the melatonin group.Trazodone 50 mg/day, clonazepam 1 mg/day, and melatonin 3 mg/day were all tolerable and effective in improving sleep quality in patients with PD.Iranian Registry of Clinical Trials (registration number; IRCT20170821035819N2).© 2022. Fondazione Società Italiana di Neurologia.

Late sleep timing is prevalent in early childhood and a risk factor for poor behavioral and health outcomes. Sleep timing is influenced by the phase of the circadian clock, with later circadian timing linked to delayed sleep onset in young children. Light is the strongest zeitgeber of circadian timing and, in adults, evening light produces circadian phase delay in an intensity-dependent manner. The intensity-dependent circadian phase-shifting response to evening light in children, however, is currently unknown. In the present study, 33 healthy, good-sleeping children aged 3.0 to 4.9 years (M = 4.14 years, 39% male) completed a 10-day between-subjects protocol. Following 7 days of a stable sleep schedule, an in-home dim-light circadian assessment was performed. Children remained in dim-light across 3 days (55 h), with salivary melatonin collected in regular intervals throughout each evening. Phase-shifting effects of light exposure were determined via changes in the timing of the dim-light melatonin onset (DLMO) prior to (Day 8) and following (Day 10) a light exposure stimulus. On Day 9, children were exposed to a 1 h light stimulus in the hour before their habitual bedtime. Each child was randomly assigned to one intensity between 5 and 5000 lux (4.5-3276 melanopic EDI). Across light intensities, children showed significant circadian phase delays, with an average phase delay of 56.1 min (SD = 33.6 min), and large inter-individual variability. No relationship between light intensity and magnitude of the phase shift was observed. However, a greater percentage of melatonin suppression during the light exposure was associated with a greater phase delay ( r = −0.73, p &lt; 0.01). These findings demonstrate that some young children may be highly sensitive to light exposure in the hour before bedtime and suggest that the home lighting environment and its impact on circadian timing should be considered a possible contributor to behavioral sleep difficulties.

A rare type of ganglion cell in mammalian retina is directly photosensitive. These novel retinal photoreceptors express the photopigment melanopsin. They send axons directly to the suprachiasmatic nucleus (SCN), intergeniculate leaflet (IGL), and olivary pretectal nucleus (OPN), thereby contributing to photic synchronization of circadian rhythms and the pupillary light reflex. Here, we sought to characterize more fully the projections of these cells to the brain. By targeting tau-lacZ to the melanopsin gene locus in mice, ganglion cells that would normally express melanopsin were induced to express, instead, the marker enzyme beta-galactosidase. Their axons were visualized by X-gal histochemistry or anti-beta-galactosidase immunofluorescence. Established targets were confirmed, including the SCN, IGL, OPN, ventral division of the lateral geniculate nucleus (LGv), and preoptic area, but the overall projections were more widespread than previously recognized. Targets included the lateral nucleus, peri-supraoptic nucleus, and subparaventricular zone of the hypothalamus, medial amygdala, margin of the lateral habenula, posterior limitans nucleus, superior colliculus, and periaqueductal gray. There were also weak projections to the margins of the dorsal lateral geniculate nucleus. Co-staining with the cholera toxin B subunit to label all retinal afferents showed that melanopsin ganglion cells provide most of the retinal input to the SCN, IGL, and lateral habenula and much of that to the OPN, but that other ganglion cells do contribute at least some retinal input to these targets. Staining patterns after monocular enucleation revealed that the projections of these cells are overwhelmingly crossed except for the projection to the SCN, which is bilaterally symmetrical.(c) 2006 Wiley-Liss, Inc.

One of the possible causes of disturbed circadian rhythms and sleep in the elderly may be impaired photic input to the circadian clock. Age-related changes in lens density are known to reduce the transmission of short wavelength light, which has been shown to be most effective in suppressing nocturnal melatonin. The aim of the study therefore was to investigate age-related changes in melatonin suppression in response to short and medium wavelength light. Young premenopausal (n=13) and postmenopausal (n=21) women were exposed to 30 min of monochromatic light at two different wavelengths and irradiances (lambda(max) 456 nm: 3.8 and 9.8 microW/cm(2); lambda(max) 548 nm: 28 and 62 microW/cm(2)). Melatonin suppression was compared across light treatments and between age groups. Significantly reduced melatonin suppression was noted in the elderly subjects following exposure to short wavelength (456 nm) light compared to the young subjects. These results are likely to reflect age-related changes in lens density.

At its best, human-centric lighting considers the visual and non-visual effects of light in support of positive human outcomes. At its worst, it is a marketing phrase used to healthwash lighting products or lighting design solutions. There is no doubt that environmental lighting contributes to human health, but how might one practice human-centric lighting given both the credible potential and the implausible hype? Marketing literature is filled with promises. Technical lighting societies have summarized the science but have not yet offered design guidance. Meanwhile, designers are in the middle, attempting to distinguish credible knowledge from that which is dubious to make design decisions that affect people directly. This article is intended to: (1) empower the reader with fundamental understandings of ways in which light affects health; (2) provide a process for human-centric lighting design that can dovetail with the decision-making process that is already a part of a designer's workflow.

Light exerts a strong non-visual influence on human physiology and behavior. Additionally light is known to affect sleep indirectly through the phase shifting of circadian rhythms, and directly, promoting alertness in humans and sleep in nocturnal species. Little attention has been paid to the direct non-image-forming influence of light until recently with the discovery and emerging knowledge on melanopsin, a photopigment which is maximally sensitive to the blue spectrum of light and expressed in a subset of intrinsically photosensitive retinal ganglion cells. Indeed, the development of transgenic mouse models targeting different phototransduction pathways has allowed researchers to decipher the mechanisms by which mammals adapt sleep to their light environment. This review summarizes the novel concepts and discrepancies from recent publications relating to the non-circadian effects of light on sleep and waking. Specifically, we discuss whether darkness, in addition to light, affects their quality. Furthermore, we seek to understand whether longer sustained periods of light exposure can influence sleep, if the direct photic regulation depends on time of day, and whether this affects the homeostatic sleep process. Moreover, the neural pathways by which light exerts a direct influence on sleep will be discussed including the respective role of rods/cones and melanopsin. Finally, we suggest that light weighs on the components of the flip-flop switch model to induce respectively sleep or waking, in nocturnal and diurnal animals. Taking these data into account we therefore propose a novel model of sleep regulation based on three processes; the direct photic regulation interacting with the circadian and homeostatic drives to determine the timing and quality of sleep and waking. An outlook of promising clinical and non-clinical applications of these findings will be considered as well as directions for future animal and human research. Copyright © 2013 Elsevier Ltd. All rights reserved.

This study examined whether diurnal non-image forming (NIF) effects of illuminance level on cognitive task performance depend on task difficulty and time of day. We employed a balanced crossover design with two 60-min sessions of 200 vs. 1000 lux at eye level. Digit-span task difficulty was manipulated within subjects (forward (FDST) vs. backward (BDST) digit-span task), n-back task difficulty was manipulated between subjects (n=1, 2, or 3). Bright light exposure improved FDST performance during the final measurement block, especially in the afternoon. In contrast, BDST performance deteriorated slightly under bright light in the afternoon. Two-back performance was significantly worse under bright light in the afternoon, while no effect of illuminance level was found on 3-back performance. Thus, the more difficult BDST was affected differently by light intensity as compared to the easier FDST. N-back accuracy, however, did not confirm this role of task difficulty. Future studies should investigate whether similar results hold for other types of tasks and how other variables (e.g., time of day, physiological arousal, or other task characteristics) may influence the direction and magnitude of NIF effects on performance.Copyright © 2015 Elsevier B.V. All rights reserved.

Underground workplaces are an important element in modem urban planning. As a result, an increasing but unquantified proportion of the population is being regularly exposed to them. We narratively reviewed the literature on the range of possible environmental exposures, and the possible health effects, to identify future research directions. There is a large but mainly observational research literature on likely underground exposures, including effects of artificial lighting, shift working and light at night on circadian disruptions and associated health effects. There are five studies comparing underground and aboveground environments. Shift working, artificial lighting and poor sleep quality leading to circadian disruption is one physiologic pathway. Working underground may increase exposure to these risks, and may also be associated with vitamin D deficiency, sick building syndrome, excessive noise, radon exposure, and negative psychological effects. In order to plan appropriate interventions, we need to expand our knowledge of the health effects of underground environments. Larger and longer-term studies are required to measure a range of human factors, environmental exposures and confounders. Controlled trials with health economic analyses of new lighting technologies are also required.

The circadian pacemaker is differentially sensitive to the resetting effects of retinal light exposure, depending upon the circadian phase at which the light exposure occurs. Previously reported human phase response curves (PRCs) to single bright light exposures have employed small sample sizes, and were often based on relatively imprecise estimates of circadian phase and phase resetting. In the present study, 21 healthy, entrained subjects underwent pre‐ and post‐stimulus constant routines (CRs) in dim light (∼2–7 lx) with maintained wakefulness in a semi‐recumbent posture. The 6.7 h bright light exposure stimulus consisted of alternating 6 min fixed gaze (∼10 000 lx) and free gaze (∼5000–9000 lx) exposures. Light exposures were scheduled across the circadian cycle in different subjects so as to derive a PRC. Plasma melatonin was used to determine the phase of the onset, offset, and midpoint of the melatonin profiles during the CRs. Phase shifts were calculated as the difference in phase between the pre‐ and post‐stimulus CRs. The resultant PRC of the midpoint of the melatonin rhythm revealed a characteristic type 1 PRC with a significant peak‐to‐trough amplitude of 5.02 h. Phase delays occurred when the light stimulus was centred prior to the critical phase at the core body temperature minimum, phase advances occurred when the light stimulus was centred after the critical phase, and no phase shift occurred at the critical phase. During the subjective day, no prolonged ‘dead zone’ of photic insensitivity was apparent. Phase shifts derived using the melatonin onsets showed larger magnitudes than those derived from the melatonin offsets. These data provide a comprehensive characterization of the human PRC under highly controlled laboratory conditions.

Eight healthy elderly women aged 56-72 years (mean age: 67.4 years) participated in this study. They were exposed to moderately bright light (1000 lux) for 1h in the morning every 6 days in their homes. Moderately bright light improved self evaluations for alertness, mood, motivation, happiness, refreshment, concentration and appetite after the second exposure to the light. Sleep maintenance, anxiety and integrated sleep feeling also improved after the fourth exposure to the light. The phase of rectal temperature rhythm did not change in a moderately bright light condition. These results suggest that bright light influences sleep quality and self evaluations without changing the biological rhythm phase.

Sleep structure was measured in five healthy elderly men in their homes. The subjects were exposed to bright light (6000 lx) for 30 min in the morning or instructed to sit in front of a desktop lighting device without light. Relative to the control conditions, bright light exposure significantly decreased time in bed and the number of awakenings. Rapid eye movement sleep was significantly fragmented by stage 1 sleep in the control condition compared with the bright light condition. These findings indicate that a short duration of morning bright light changes sleep structure and is effective in maintaining sleep.

Light has profoundly influenced the evolution of life on earth. As widely appreciated, light enables us to generate images of our environment. However, light - through intrinsically photosensitive retinal ganglion cells (ipRGCs) - also influences behaviours that are essential for our health and quality of life but are independent of image formation. These include the synchronization of the circadian clock to the solar day, tracking of seasonal changes and the regulation of sleep. Irregular light environments lead to problems in circadian rhythms and sleep, which eventually cause mood and learning deficits. Recently, it was found that irregular light can also directly affect mood and learning without producing major disruptions in circadian rhythms and sleep. In this Review, we discuss the indirect and direct influence of light on mood and learning, and provide a model for how light, the circadian clock and sleep interact to influence mood and cognitive functions.

The Corona Virus Disease-19 (COVID-19) pandemic has evolved into the largest public health event in the world. Earlier COVID-19 studies have reported that the pandemic caused widespread impacts on mental health and sleep in the general population. However, it remains largely unknown how the prevalence of mental health problems and sleep disturbance developed and interacted in adolescents at different times in the epidemic.831 teenagers (aged 14-19) underwent a longitudinal follow-up study to evaluate the prevalence of mental health problems and sleep disturbance among adolescents before, during, and after the COVID-19 breakout in China and to explore the interaction between mental health and sleep across the three measurements. The chronotype, anxiety and depression level, sleep quality, and insomnia were investigated during each measurement.The adolescents had delayed sleep onset and sleep offset time, longer sleep duration during the quarantine than before and after the epidemic, whereas their chronotype tended to morning type during the epidemic. Yet, the highest prevalence of anxiety, depression, poor sleeper, and insomnia symptoms were observed before but not during the COVID-19 breakout. The females and adolescents who were eveningness type showed significantly higher anxiety and depression levels, poorer sleep quality, and severe insomnia status than the males and the intermediate and morning types. Sleep disturbance was positively associated with mental problems among three measurements. Pre-measured depression level significantly predicted sleep disturbance level at follow-ups.These findings suggested that adolescents' high prevalence of mental health and sleep problems occurred before the COVID breakout and decreased during and after the epidemic. Gender and chronotype were significant risk factors associated with affective and sleep disturbances. Depression positively predicted later sleep problems, but not vice versa.Copyright © 2021 Elsevier B.V. All rights reserved.

Light is known to elicit non-image-forming responses, such as effects on alertness. This has been reported especially during light exposure at night. Nighttime results might not be translatable to the day. This article aims to provide an overview of (1) neural mechanisms regulating alertness, (2) ways of measuring and quantifying alertness, and (3) the current literature specifically regarding effects of different intensities of white light on various measures and correlates of alertness during the daytime. In general, the present literature provides inconclusive results on alerting effects of the intensity of white light during daytime, particularly for objective measures and correlates of alertness. However, the various research paradigms employed in earlier studies differed substantially, and most studies tested only a limited set of lighting conditions. Therefore, the alerting potential of exposure to more intense white light should be investigated in a systematic, dose-dependent manner with multiple correlates of alertness and within one experimental paradigm over the course of day.

Under real-life conditions, increased light exposure during wakefulness seems associated with improved sleep quality, quantified as reduced time awake during bed time, increased time spent in non-rapid eye movement (NREM) sleep, or increased power of the electroencephalogram delta band (0.5-4 Hz). The causality of these important relationships and their dependency on circadian phase and/or time awake has not been studied in depth. To disentangle possible circadian and homeostatic interactions, we employed a forced desynchrony protocol under dim light (6 lux) and under bright light (1300 lux) during wakefulness. Our protocol consisted of a fast cycling sleep-wake schedule (13 h wakefulness-5 h sleep; 4 cycles), followed by 3 h recovery sleep in a within-subject cross-over design. Individuals (8 men) were equipped with 10 polysomnography electrodes. Subjective sleep quality was measured immediately after wakening with a questionnaire. Results indicated that circadian variation in delta power was only detected under dim light. Circadian variation in time in rapid eye movement (REM) sleep and wakefulness were uninfluenced by light. Prior light exposure increased accumulation of delta power and time in NREM sleep, while it decreased wakefulness, especially during the circadian wake phase (biological day). Subjective sleep quality scores showed that participants rated their sleep quality better after bright light exposure while sleeping when the circadian system promoted wakefulness. These results suggest that high environmental light intensity either increases sleep pressure buildup during wakefulness or prevents the occurrence of micro-sleep, leading to improved quality of subsequent sleep.

Light-induced improvements in alertness are more prominent during nighttime than during the day, suggesting that alerting effects of light may depend on internal clock time or wake duration. Relative contributions of both factors can be quantified using a forced desynchrony (FD) designs. FD designs have only been conducted under dim light conditions (<10 lux) since light above this amount can induce non-uniform phase progression of the circadian pacemaker (also called relative coordination). This complicates the mathematical separation of circadian clock phase from homeostatic sleep pressure effects. Here we investigate alerting effects of light in a novel 4 × 18 h FD protocol (5 h sleep, 13 h wake) under dim (6 lux) and bright light (1300 lux) conditions. Hourly saliva samples (melatonin and cortisol assessment) and 2-hourly test sessions were used to assess effects of bright light on subjective and objective alertness (electroencephalography and performance). Results reveal (1) stable free-running cortisol rhythms with uniform phase progression under both light conditions, suggesting that FD designs can be conducted under bright light conditions (1300 lux), (2) subjective alerting effects of light depend on elapsed time awake but not circadian clock phase, while (3) light consistently improves objective alertness independent of time awake or circadian clock phase. Reconstructing the daily time course by combining circadian clock phase and wake duration effects indicates that performance is improved during daytime, while subjective alertness remains unchanged. This suggests that high-intensity indoor lighting during the regular day might be beneficial for mental performance, even though this may not be perceived as such.

This meta-analysis examined the mean sleep duration and patterns in Chinese older adult population. A literature search was systematically conducted covering major English (PubMed, Embase and PsycINFO) and Chinese (Chinese National Knowledge Infrastructure (CNKI), WanFang and SinoMed) databases. Data in studies with the mean and standard deviation of sleep duration and/or the proportion of short and long sleep durations in Chinese older adults were extracted and pooled using random-effects models. Subgroup analyses were conducted according to gender, region, area, survey time and sample size. A total of 36 studies with 150,616 subjects were included for analyses. The pooled mean sleep duration of 21 studies with available data was 6.82 hours/day (95% CI: 6.59-7.05 hours/day). The estimated proportions of sleep duration <5 hours/day, <6 hours/day, <7 hours/day were 18.8% (95% CI: 1.7%-35.9%), 26.7% (95% CI: 19.7%-33.7%) and 42.3% (95% CI: 34.8%-49.8%), respectively. The pooled proportions for long sleepers were 22.6% (95% CI: 13.9%-31.4%) (>8 hours/day) and 17.6% (95% CI: 12.4%-22.9%) (>9 hours/day). Given the adverse effects of unhealthy sleep patterns, health professionals should pay more attention to sleep patterns in this population in China.

Sleep is regulated by both homeostatic and circadian mechanisms. The latter, termed 'process c', helps synchronize sleep-wake patterns to the appropriate time of the day. However, in the absence of a circadian clock, overall sleep-wake rhythmicity is preserved and remains synchronized to the external light-dark cycle, indicating that there is an additional, clock-independent photic input to sleep. We found that the direct photic regulation of sleep in mice is predominantly mediated by melanopsin (OPN4)-based photoreception of photosensitive retinal ganglion cells (pRGCs). Moreover, OPN4-dependent sleep regulation was correlated with the activation of sleep-promoting neurons in the ventrolateral preoptic area and the superior colliculus. Collectively, our findings describe a previously unknown pathway in sleep regulation and identify the pRGC/OPN4 signaling system as a potentially new pharmacological target for the selective manipulation of sleep and arousal states.

Many adolescents fall asleep too late to get enough sleep (8-10 h) on school nights. Morning bright light advances circadian rhythms and could help adolescents fall asleep earlier. Morning bright light treatment before school, however, is difficult to fit into their morning schedule; weekends are more feasible. We examined phase advances in response to morning light treatment delivered over one weekend. Thirty-seven adolescents (16 males; 14.7-18.0 years) who reported short school-night sleep (≤7 h) and late bedtimes (school-nights ≥23:00; weekend/non-school nights ≥24:00) slept as usual at home for ∼2 weeks ("baseline") and then kept a fixed sleep schedule (baseline school-night bed and wake-up times ±30 min) for ∼1 week before living in the lab for one weekend. Sleep behavior was measured with wrist actigraphy and sleep diary. On Saturday morning, we woke each participant 1 h after his/her midpoint of baseline weekend/non-school night sleep and 1 h earlier on Sunday. They remained in dim room light (∼20 lux) or received 1.5 or 2.5 h of intermittent morning bright light (∼6000 lux) on both mornings. The dim light melatonin onset (DLMO), a phase marker of the circadian timing system, was measured on Friday and Sunday evenings to compute the weekend circadian phase shift. The dim room light and 1.5-h bright light groups advanced the same amount (0.6 ± 0.4 and 0.6 ± 0.5 h). The 2.5-h bright light group advanced 1.0 ± 0.4 h, which was significantly more than the other groups. These data suggest that it is possible to phase advance the circadian clock of adolescents who have late bedtimes and short school-night sleep in one weekend using light that begins shortly after their sleep midpoint.Copyright © 2020 Misiunaite, Eastman and Crowley.

Evening bright light exposure is reported to ameliorate daytime sleepiness and age-related sleep complaints, and also delays the timing of circadian rhythms. We tested whether evening light exposure given to older adults with sleep-wake complaints would delay the timing of their circadian rhythms with respect to their sleep timing, thereby reducing evening sleepiness and improving subsequent sleep quality. We examined the impact of evening light exposure from two different light sources on subjective alertness, EEG activity during wakefulness, and sleep stages. Ten healthy older adults with sleep complaints (mean age=63.3 years; 6F) participated in a 13-day study. After three baseline days, circadian phase was assessed. On the evening of days 5-8 the subjects were exposed for 2h to either polychromatic blue-enriched white light or standard white fluorescent light, and on the following day circadian phase was re-assessed. Subjects were allowed to leave the laboratory during all but the two days when the circadian phase assessment took place. Evening assessments of subjective alertness, and wake and sleep EEG data were analyzed. Subjective alertness and wake EEG activity in the alpha range (9.75-11.25 Hz) were significantly higher during light exposures when compared to the pre-light exposure evening (p<0.05). The light exposures produced circadian phase shifts and significantly prolonged latency to rapid eye-movement (REM) sleep for both light groups (p<0.05). The increase in wake EEG alpha activity during the light exposures was negatively correlated with REM sleep duration (p<0.05). Evening light exposure could benefit older adults with early evening sleepiness, without negatively impacting the subsequent sleep episode.Copyright © 2011 Elsevier B.V. All rights reserved.

Chronic circadian misalignment between the internal and environmental rhythms, which is typically related to night-shift work and clock-gene variants, is associated with disruption of suprachiasmatic nucleus function and increased risk of insomnia. Under controlled laboratory conditions, light at night (LAN) suppresses melatonin secretion, delays the internal biological rhythm, and reduces sleepiness. Therefore, LAN exposure may cause circadian misalignment and insomnia, though it remains unclear in real-life situations whether LAN exposure is associated with insomnia. To evaluate an association between LAN exposure and sleep quality in home settings, we conducted a cross-sectional community-based study in 857 elderly individuals (mean age, 72.2 years). We evaluated bedroom light intensity using a light meter and subjectively and objectively measured sleep quality using the Pittsburgh Sleep Quality Index and an actigraph, respectively, along with urinary 6-sulfatoxymelatonin excretion. Compared with the lowest quartile group of LAN intensity, the highest quartile group revealed a significantly higher odds ratio (OR) for subjective insomnia in a multivariate model adjusted for age, gender, body mass index, daytime physical activity, urinary 6-sulfatoxymelatonin excretion, bedtime, rising time, and day length (adjusted OR, 1.61, 95% confidence interval, 1.05-2.45, p=0.029). In addition, higher OR for subjective insomnia was significantly associated with the increase in quartiles of LAN intensity (ptrend=0.043). Consistently, we observed significant association trends between the increase in quartiles of LAN intensity and poorer actigraphic sleep quality, including decreased sleep efficiency, prolonged sleep-onset latency, increased wake-after-sleep onset, shortened total sleep time, and delayed sleep-mid time in multivariate models adjusted for the covariates mentioned above (all ptrend<0.001). In conclusion, we demonstrated that LAN exposure in home settings is significantly associated with both subjectively and objectively measured sleep quality in a community-based elderly population.

Ambient light levels influence visual system size in birds and primates. Here, we argue that the same is true for humans. Light levels, in terms of both the amount of light hitting the Earth's surface and day length, decrease with increasing latitude. We demonstrate a significant positive relationship between absolute latitude and human orbital volume, an index of eyeball size. Owing to tight scaling between visual system components, this will translate into enlarged visual cortices at higher latitudes. We also show that visual acuity measured under full-daylight conditions is constant across latitudes, indicating that selection for larger visual systems has mitigated the effect of reduced ambient light levels. This provides, to our knowledge, the first support that light levels drive intraspecific variation in visual system size in the human population.

For decades, rods and cones were thought to be the only photoreceptors in the mammalian retina. However, a population of atypical photoreceptive retinal ganglion cells (RGCs) expresses the photopigment melanopsin and is intrinsically photosensitive (ipRGCs). These ipRGCs are crucial for relaying light information from the retina to the brain to control circadian photoentrainment, pupillary light reflex, and sleep. ipRGCs were initially described as a uniform population involved solely in signaling irradiance for non-image forming functions. Recent work, however, has uncovered that ipRGCs are unexpectedly diverse at the molecular, cellular and functional levels, and could even be involved in image formation. This review summarizes our current understanding of the diversity of ipRGCs and their various roles in modulating behavior.Copyright © 2011 Elsevier Ltd. All rights reserved.

It was investigated whether cognitive performance shows a circadian rhythm during a 50 h-long forced desynchrony sleep-wake-schedule. We asked whether it would be possible to estimate the circadian period of cognitive performance under such circumstances and how strong it correlates to subjective sleepiness rating as well as body temperature.

To date, it is largely unknown which light settings define the optimum to steer alertness and cognitive control during regular daytime working hours. In the current article, we used a multimeasure approach combined with a relatively large sample size ( N = 60) and a large range of intensity levels (20-2000 lux at eye level) to investigate the dose-dependent relationship between light and correlates of alertness and executive control during regular working hours in the morning and afternoon. Each participant was exposed to a single-intensity light level for 1 h after a 30-min baseline phase (100 lux at the eye) in the morning and afternoon (on separate days) during their daily routine. Results revealed no clear dose-dependent relationships between 1-h daytime light exposure and correlates of alertness or executive control. Subjective correlates showed only very modest linear relationships with the log-transformed illuminance, and we found no significant effects of light intensity on the behavioral and physiological indicators. Overall, these results suggest that daytime exposure to more intense light, at least for 1 h of exposure, may not systematically benefit alertness or executive functioning. However, future research is required to investigate effects of longer exposure durations and potential moderations by prior light exposure, personal characteristics, and spectrum.

Periodic, well timed exposure to light is important for our health and wellbeing. Light, in particular in the blue part of the spectrum, is thought to affect alertness both indirectly, by modifying circadian rhythms, and directly, giving rise to acute effects. We performed a systematic review of empirical studies on direct, acute effects of light on alertness to evaluate the reliability of these effects. In total, we identified 68 studies in which either light intensity, spectral distribution, or both were manipulated, and evaluated the effects on behavioral measures of alertness, either subjectively or measured in reaction time performance tasks. The results show that increasing the intensity of polychromatic white light has been found to increase subjective ratings of alertness in a majority of studies, though a substantial proportion of studies failed to find significant effects, possibly due to small sample sizes or high baseline light intensities. The effect of the color temperature of white light on subjective alertness is less clear. Some studies found increased alertness with higher color temperatures, but other studies reported no detrimental effects of filtering out the short wavelengths from the spectrum. Similarly, studies that used monochromatic light exposure showed no systematic pattern for the effects of blue light compared to longer wavelengths. Far fewer studies investigated the effects of light intensity or spectrum on alertness as measured with reaction time tasks and of those, very few reported significant effects. In general, the small sample sizes used in studies on acute alerting effects of light make it difficult to draw definitive conclusions and better powered studies are needed, especially studies that allow for the construction of dose-response curves.Copyright © 2017 Elsevier B.V. All rights reserved.

Familial advanced sleep phase syndrome (FASPS) is an autosomal dominant circadian rhythm variant; affected individuals are "morning larks" with a 4-hour advance of the sleep, temperature, and melatonin rhythms. Here we report localization of the FASPS gene near the telomere of chromosome 2q. A strong candidate gene (hPer2), a human homolog of the period gene in Drosophila, maps to the same locus. Affected individuals have a serine to glycine mutation within the casein kinase Iepsilon (CKIepsilon) binding region of hPER2, which causes hypophosphorylation by CKIepsilon in vitro. Thus, a variant in human sleep behavior can be attributed to a missense mutation in a clock component, hPER2, which alters the circadian period.

Patients with Primary Biliary Cholangitis (PBC) exhibit delayed sleep-wake habits, disturbed night sleep and daytime sleepiness/fatigue. Such combination of symptoms is reminiscent of delayed sleep-wake phase disorder (DSPD), which benefits from morning light treatment. The aim of the present pilot study was to test the effect of morning light treatment in a group of 13 well-characterized patients with PBC [all females; (mean +/- SD) 53 +/- 10 years]. Six healthy individuals (4 females, 57 +/- 14 years) and 7 patients with cirrhosis (1 female, 57 +/- 12 years) served as controls and diseased controls, respectively. At baseline, all participants underwent an assessment of quality of life, diurnal preference, sleep quality/timing (subjective plus actigraphy), daytime sleepiness, and urinary 6-sulphatoxymelatonin (aMT6s) rhythmicity. Then they underwent a 15-day course of morning bright light treatment, immediately after getting up (light box, 10,000 lux, 45 min) whilst monitoring sleep-wake patterns and aMT6s rhythmicity. At baseline, both patients with PBC and patients with cirrhosis had significantly worse subjective sleep quality compared to controls. In patients with PBC, light treatment resulted in an improvement in subjective sleep quality and a reduction in daytime sleepiness. In addition, both their sleep onset and get-up time were significantly advanced. Finally, the robustness of aMT6s rhythmicity (i.e., strength of the cosinor fit) increased after light administration but post-hoc comparisons were not significant in any of the groups. In conclusion, a brief course of morning bright light treatment had positive effects on subjective sleep quality, daytime sleepiness, and sleep timing in patients with PBC. This unobtrusive, side-effect free, non-pharmacological treatment is worthy of further study.

Dispositional optimism has been related to beneficial influences on physical health outcomes. However, its links to global sleep quality and the psychological mediators responsible for such associations are less studied. This study thus examined if trait optimism predicted global sleep quality, and if measures of subjective well-being were statistical mediators of such links. A community sample of 175 participants (93 men, 82 women) completed measures of trait optimism, depression, and life satisfaction. Global sleep quality was assessed using the Pittsburgh Sleep Quality Index. Results indicated that trait optimism was a strong predictor of better PSQI global sleep quality. Moreover, this association was mediated by depression and life satisfaction in both single and multiple mediator models. These results highlight the importance of optimism for the restorative process of sleep, as well as the utility of multiple mediator models in testing distinct psychological pathways.

Purpose The International Commission on Illumination (CIE) recommends researchers to investigate a wide variety of behavioural and health outcomes. However, researchers often investigate only a part of occupational health (OH) in relation to light. A literature study (2002-2017) regarding the relationship between office lighting conditions and OH was performed to identify gaps and methodological issues. Method The OH outcomes investigated in this paper were grouped according to the International Classification of Diseases and analysed per category: physical and physiological health, mental health, eye health, sleep parameters and visual comfort. Results Findings from the literature study (20 eligible papers) showed that all OH aspects were mostly but not exclusively measured subjectively. Furthermore, most studies investigated only a fraction of office lighting parameters and OH aspects. Conclusions It seems that Correlated Colour Temperature (CCT) and illuminance mainly correlate with OH. However, this may also be explained by gaps and methodological issues in studies described in eligible papers. Based on the literature study, an overview was composed elucidating gaps and methodological issues of office lighting and OH studies. It can be used to design and target the purpose of light and health research.

Few studies have examined the association between sleep duration trajectories and hypertension. This study aims to examine association of sleep duration trajectories with risk of hypertension and its related factors.This study used longitudinal data for 7,397 adults who provided valid responses in questionnaire with regard to information of sleep and hypertension from the China Health and Nutrition Survey (2004-2011). Subgroup analyses included 5,532 participants in whom hypertension-related factors were measured using blood samples. Latent class trajectory analysis was used to identify different sleep duration trajectories. Multivariate Cox regression models and general linear regression models were used to assess association of trajectories with hypertension and its related factors.Compared to stable sleep duration around 8 hours, the trajectory showing a persistent decrease in sleep duration with aging was significantly associated with increased risk of hypertension (hazard ratio 1.12, 95% confidence interval 1.01-1.24), whereas no significant association was observed between the trajectory showing an increase in sleep duration to 9 hours with aging and risk of hypertension (hazard ratio 1.05, 95% confidence interval 0.93-1.19). Further, uric acid levels, fasting glucose levels, total cholesterol levels, and apolipoprotein B levels were significantly higher in the trajectory showing a persistent decrease in sleep duration with aging than the other two trajectories (all P <.05).Decreasing sleep duration during aging is significantly associated with increased risk of hypertension and higher levels of its biomarkers throughout adulthood.© 2020 American Academy of Sleep Medicine.

The antidepressant and sleep-promoting effects of light exposure might be useful for treating age-related mood and sleep disorders. In view of recent evidence suggesting beneficial effects of morning light, this study examined the associations of mood and sleep with morning light exposure, 24 h environmental illumination, and the degree to which the volunteers' bedroom windows were covered in the morning. We examined 459 postmenopausal women participating an ancillary study of the Women's Health Initiative conducted at the University of California, San Diego Clinical Center, San Diego, CA, USA. At baseline, volunteers completed a 4-week sleep-recall questionnaire. Volunteers were then assessed for 5-7 days in their home environments with actigraphic wrist monitors. During home recording, self-reported mood was assessed. Morning illumination during the first 4 h after arising, 24-h illumination mesor (cosine-fitted mean), and illumination acrophase (cosine-fitted peak time) were calculated. Sleep was scored each night using validated wrist actigraphic methods. A sleep diary was completed each morning. During two 24-h periods, urine was collected approximately every 2 h during wakefulness and following any voidings during the sleep period. Cosine-fitting established the acrophase of urinary 6-sulfatoxymelatonin (aMT6s) excretion. Morning illumination and 24-h illumination were modestly associated with better mood and sleep. Associations of light with mood and sleep were consistently greater for subjects whose body clocks were delayed relative to the group median. Less morning window covering in the subjects' bedrooms was associated with more morning light and less depressed mood. The results suggest that both morning and 24-h light exposure may be beneficial for older adults.

Evidence-based treatments for post-traumatic stress disorder (PTSD) have poor uptake and remission rates, suggesting that alternative treatments are needed. Morning bright light may be an effective treatment for PTSD given its established effects on mood and sleep, however, there are no published trials.We conducted a placebo-controlled pilot trial of a wearable light device, the Re-timer®, for individuals with probable PTSD. Individuals were randomly assigned to the active Re-timer® (n = 9) or a placebo Re-timer® dimmed with neutral density filters (n = 6). Participants self-administered the treatment at home 1 hr each morning over 4 weeks. PTSD and depression symptoms were assessed at pre- and post-treatment.The Re-timer® was well tolerated and the perceived benefit was high, though treatment adherence was only moderate. Those in the active group were more likely to achieve a minimal clinically important change in PTSD and depression symptoms and had larger symptom reductions than those in the placebo group CONCLUSIONS: A wearable morning light treatment was acceptable and feasible for patients with probable PTSD. This study provides initial proof-of-concept that light treatment can improve PTSD. A larger trial is warranted to establish treatment efficacy. NCT#: 03513848.© 2019 Wiley Periodicals, Inc.