Non-visual effects of light on melatonin, alertness and cognitive performance: can blue-enriched light keep us alert?

Towards an evidence-based integrative lighting score: a proposed multi-level approach

Background: Human circadian clocks are synchronized daily with the external light-dark cycle and entrained to the 24-hour day. There is increasing evidence that a lack of synchronization and circadian entrainment can lead to adverse health effects. Beyond vision, light plays a critical role in modulating many so-called non-visual functions, including sleep-wake cycles, alertness, mood and endocrine functions. To assess (and potentially optimize) the impact of light on non-visual functions, it is necessary to know the exact 'dose' (i.e. spectral irradiance and exposure duration at eye level) of 24-hour light exposures, but also to include metadata about the lighting environment, individual needs and resources.

Problem statement: To address this problem, a new assessment tool is needed that uses existing metrics to provide metadata and information about light quality and quantity from all sources. In this commentary, we discuss the need to develop an evidence-based integrative lighting score that is tailored to specific audiences and lighting environments. We will summarize the most compelling evidence from the literature and outline a future plan for developing such a lighting score using internationally accepted metrics, stakeholder and user feedback.

Conclusion: We propose a weighting system that combines light qualities with physiological and behavioral effects, and the use of mathematical modelling for an output score. Such a scoring system will facilitate a holistic assessment of a lighting environment, integrating all available light sources.

Evening prolonged relatively low melanopic equivalent daylight illuminance light exposure increases arousal before and during sleep without altering sleep structure

Light can influence many psychophysiological functions beyond vision, including alertness, circadian rhythm, and sleep, namely the non-image forming (NIF) effects of light. Melanopic equivalent daylight illuminance (mel-EDI) is currently recommended as the predictor of the NIF effects of light. Although light dose is also critical for entraining and regulating circadian cycle, it is still unknown whether relatively low mel-EDI light exposure for prolonged duration in the evening would affect pre-sleep arousal and subsequent sleep. In all, 18 healthy college students (10 females, mean [standard deviation] age 21.67 [2.03] years) underwent 2 experimental nights with a 1 week interval in a simulated bedroom environment. During experimental nights, participants were either exposed to high or low mel-EDI light (73 versus 38 lx mel-EDI, 90 versus 87 photopic lx at eye level, 150 photopic lx at table level) for 3.5 h before regular bedtime, and their sleep was monitored by polysomnography. Subjective sleepiness, mood, and resting-state electroencephalography during light exposure were also investigated. Results showed no significant differences in sleep structure and sleep quality between the two light conditions, whereas 3.5 h of exposure to high versus low mel-EDI light induced marginally higher physiological arousal in terms of a lower delta but higher beta power density before sleep, as well as a lower delta power density during sleep. Moreover, participants felt happier before sleep under exposure to high versus low mel-EDI light. These findings together with the current literature suggest that evening prolonged relatively low mel-EDI light exposure may mildly increase arousal before and during sleep but affected sleep structure less.

Acute effects of light during daytime on central aspects of attention and affect: A systematic review

Light regulates both image- and various non-image forming responses in humans, including acute effects on attention and affect. To advance the understanding of light's immediate effects, this systematic review describes the acute effects of monochromatic/narrow bandwidth and polychromatic white light during daytime on distinct aspects of attention (alertness, sustained attention, working memory, attentional control and flexibility), and measures of affect (self-report measures, performance-based tests, psychophysiological measures) in healthy, adult human subjects. Original, peer-reviewed (quasi-) experimental studies published between 2000 and May 2024 were included according to predefined inclusion and exclusion criteria. Study quality was assessed, and results were synthesized across aspects of attention and affect and grouped according to light interventions; monochromatic/narrowband-width or polychromatic white light (regular white, bright white, and white with high correlated color temperature (CCT)). Results from included studies (n = 62) showed that alertness and working memory were most affected by light. Electroencephalographic markers of alertness improved the most with exposure to narrow bandwidth long-wavelength light, regular white, and white light with high CCT. Self-reported alertness and measures of working memory improved the most with bright white light. Results from studies testing the acute effects on sustained attention and attentional control and flexibility were inconclusive. Performance-based and psychophysiological measures of affect were only influenced by narrow bandwidth long-wavelength light. Polychromatic white light exerted mixed effects on self-reported affect. Studies were strongly heterogeneous in terms of light stimuli characteristics and reporting of light stimuli and control of variables influencing light's acute effects.

Blue Light and Digital Screens Revisited: A New Look at Blue Light from the Vision Quality, Circadian Rhythm and Cognitive Functions Perspective

Research conducted over the years has established that artificial light at night (ALAN), particularly short wavelengths in the blue region (~400-500 nm), can disrupt the circadian rhythm, cause sleep disturbances, and lead to metabolic dysregulation. With the increasing number of people spending considerable amounts of time at home or work staring at digital screens such as smartphones, tablets, and laptops, the negative impacts of blue light are becoming more apparent. While blue wavelengths during the day can enhance attention and reaction times, they are disruptive at night and are associated with a wide range of health problems such as poor sleep quality, mental health problems, and increased risk of some cancers. The growing global concern over the detrimental effects of ALAN on human health is supported by epidemiological and experimental studies, which suggest that exposure to ALAN is associated with disorders like type 2 diabetes, obesity, and increased risk of breast and prostate cancer. Moreover, several studies have reported a connection between ALAN, night-shift work, reduced cognitive performance, and a higher likelihood of human errors. The purpose of this paper is to review the biological impacts of blue light exposure on human cognitive functions and vision quality. Additionally, studies indicating a potential link between exposure to blue light from digital screens and increased risk of breast cancer are also reviewed. However, more research is needed to fully comprehend the relationship between blue light exposure and adverse health effects, such as the risk of breast cancer.

Test conditions impact measures of visual, perceptual, and cognitive performance

Traditionally, visual, perceptual, and cognitive (VPC) testing is performed in well-lit, silent rooms, whilst seated, and with little incentive. Whilst this is a well-controlled setting, it may lack key features of ecological validity and therefore generalisations to real-world environments and tasks may be erroneous. In the present study, 60 participants completed tests of processing speed, divided attention, and selective attention under varying conditions of light, auditory demands, movement demands, and incentive. The results found that processing speed was significantly better in the incentive condition compared to the non-incentive condition; and in the seated and standing conditions compared to the stepping condition. Divided attention and selective attention were significantly worse in the silent condition compared to the music conditions. No significant differences were found between light and dark conditions. These findings demonstrate that performance on the VPC tests is affected by auditory conditions, movement conditions, and incentives, but not light conditions.

The cognitive impact of light: illuminating ipRGC circuit mechanisms

Ever-present in our environments, light entrains circadian rhythms over long timescales, influencing daily activity patterns, health and performance. Increasing evidence indicates that light also acts independently of the circadian system to directly impact physiology and behaviour, including cognition. Exposure to light stimulates brain areas involved in cognition and appears to improve a broad range of cognitive functions. However, the extent of these effects and their mechanisms are unknown. Intrinsically photosensitive retinal ganglion cells (ipRGCs) have emerged as the primary conduit through which light impacts non-image-forming behaviours and are a prime candidate for mediating the direct effects of light on cognition. Here, we review the current state of understanding of these effects in humans and mice, and the tools available to uncover circuit-level and photoreceptor-specific mechanisms. We also address current barriers to progress in this area. Current and future efforts to unravel the circuits through which light influences cognitive functions may inform the tailoring of lighting landscapes to optimize health and cognitive function.

Effects of calibrated blue-yellow changes in light on the human circadian clock

Evening exposure to short-wavelength light can affect the circadian clock, sleep and alertness. Intrinsically photosensitive retinal ganglion cells expressing melanopsin are thought to be the primary drivers of these effects. Whether colour-sensitive cones also contribute is unclear. Here, using calibrated silent-substitution changes in light colour along the blue-yellow axis, we investigated whether mechanisms of colour vision affect the human circadian system and sleep. In a 32.5-h repeated within-subjects protocol, 16 healthy participants were exposed to three different light scenarios for 1 h starting 30 min after habitual bedtime: baseline control condition (93.5 photopic lux), intermittently flickering (1 Hz, 30 s on-off) yellow-bright light (123.5 photopic lux) and intermittently flickering blue-dim light (67.0 photopic lux), all calibrated to have equal melanopsin excitation. We did not find conclusive evidence for differences between the three lighting conditions regarding circadian melatonin phase delays, melatonin suppression, subjective sleepiness, psychomotor vigilance or sleep.The Stage 1 protocol for this Registered Report was accepted in principle on 9 September 2020. The protocol, as accepted by the journal, can be found at https://doi.org/10.6084/m9.figshare.13050215.v1 .

Enjoying art: an evolutionary perspective on the esthetic experience from emotion elicitors

The ubiquity of human art prompted evolutionary psychologists to explore its origins as a potential adaptation to the environment. Here we focus on emotionally charged art and posit that affective affordances embedded into some artworks play a pivotal role in explaining why these artworks are enjoyed from an evolutionary perspective. Such features, recurring in various art forms, are interpreted as cues to the emotional state of others, enabling art consumers to engage in empathetic experiences and vicarious emotions. We explore the adaptive value of deriving pleasure from vicarious emotions, while also addressing the seemingly counterintuitive enjoyment of artworks that evoke negative emotions. We discuss the appreciation of vicarious emotions irrespective of their valence and maintain this appreciation to hold adaptive significance for three key reasons. Firstly, it aids art consumers in refining their interpretational schemes of internal states, potentially enhancing emotional regulation skills. Secondly, it contributes to a deeper understanding of the emotions of others, thereby fostering emotional intelligence and empathy. Lastly, the enjoyment of affectively charged artworks reinforces social cohesion by harmonizing the emotions of group members. This perspective provides a comprehensive framework for understanding the evolutionary underpinnings of the human capacity for art appreciation and emotional engagement.

Effectiveness of caffeine and blue-enriched light on cognitive performance and electroencephalography correlates of alertness in a spaceflight robotics simulation

Human cognitive impairment associated with sleep loss, circadian misalignment and work overload is a major concern in any high stress occupation but has potentially catastrophic consequences during spaceflight human robotic interactions. Two safe, wake-promoting countermeasures, caffeine and blue-enriched white light have been studied on Earth and are available on the International Space Station. We therefore conducted a randomized, placebo-controlled, cross-over trial examining the impact of regularly timed low-dose caffeine (0.3 mg per kg per h) and moderate illuminance blue-enriched white light (~90 lux, ~88 melEDI lux, 6300 K) as countermeasures, separately and combined, in a multi-night simulation of sleep-wake shifts experienced during spaceflight among 16 participants (7 F, ages 26-55). We find that chronic administration of low-dose caffeine improves subjective and objective correlates of alertness and performance during an overnight work schedule involving chronic sleep loss and circadian misalignment, although we also find that caffeine disrupts subsequent sleep. We further find that 90 lux of blue-enriched light moderately reduces electroencephalogram (EEG) power in the theta and delta regions, which are associated with sleepiness. These findings support the use of low-dose caffeine and potentially blue-enriched white light to enhance alertness and performance among astronauts and shiftworking populations.

Brain activity characteristics of RGB stimulus: an EEG study

The perception of color is a fundamental cognitive feature of our psychological experience, with an essential role in many aspects of human behavior. Several studies used magnetoencephalography, functional magnetic resonance imaging, and electroencephalography (EEG) approaches to investigate color perception. Their methods includes the event-related potential and spectral power activity of different color spaces, such as Derrington-Krauskopf-Lennie and red-green-blue (RGB), in addition to exploring the psychological and emotional effects of colors. However, we found insufficient studies in RGB space that considered combining all aspects of EEG signals. Thus, in the present study, focusing on RGB stimuli and using a data-driven approach, we investigated significant differences in the perception of colors. Our findings show that beta oscillation of green compared to red and blue colors occurs in early sensory periods with a latency shifting in the occipital region. Furthermore, in the occipital region, the theta power of the blue color decreases noticeably compared to the other colors. Concurrently, in the prefrontal area, we observed an increase in phase consistency in response to the green color, while the blue color showed a decrease. Therefore, our results can be used to interpret the brain activity mechanism of color perception in RGB color space and to choose suitable colors for more efficient performance in cognitive activities.

Effect of bright light therapy on cancer-related fatigue and related symptoms: A systematic review and meta-analysis of randomized controlled trials

OBJECTIVE

Cancer-related fatigue (CRF) is a common side effect in cancer patients, possibly due to disrupted circadian rhythms. While bright light therapy (BLT) is known to modulate circadian rhythms, its role in mitigating CRF remains unclear. This study examined the impact of BLT on CRF and other related symptoms.

METHODS

PubMed, Embase, Cochrane Library, and SCOPUS databases were searched. The trials were selected according to the PRISMA guidelines. The severity and quality of CRF and related symptoms were investigated in post-BLT intervention.

RESULTS

Twelve trials involving 691 were included. BLT significantly reduced CRF (SMD = -0.92, 95% CI: -1.45 to -0.40, p < 0.00001, I2 = 90%) and insomnia (SMD = -2.80, 95% CI: -4.61 to -0.98, I2 = 0%). Subgroup analyzes were performed based on various factors including light illuminance and intervention duration. BLT was found to be effective in both preventing and treating CRF, though it did not significantly enhance sleep quality, depression, and quality of life (QoL).

CONCLUSION

BLT is a promising intervention for managing CRF in cancer patients. Its efficacy in improving sleep quality, and insomnia, reducing depression, and enhancing QoL requires further exploration. A 4-week BLT intervention with ≥10,000 lx is recommended for preventing and treating CRF, with longer or less intense interventions also showing effectiveness. Otherwise, BLT exhibited minimal adverse effects.

Seasonal Variation in the Responsiveness of the Melanopsin System to Evening Light: Why We Should Report Season When Collecting Data in Human Sleep and Circadian Studies

It is well known that variations in light exposure during the day affect light sensitivity in the evening. More daylight reduces sensitivity, and less daylight increases it. On average days, we spend less time outdoors in winter and receive far less light than in summer. Therefore, it could be relevant when collecting research data on the non-image forming (NIF) effects of light on circadian rhythms and sleep. In fact, studies conducted only in winter may result in more pronounced NIF effects than in summer. Here, we systematically collected information on the extent to which studies on the NIF effects of evening light include information on season and/or light history. We found that more studies were conducted in winter than in summer and that reporting when a study was conducted or measuring individual light history is not currently a standard in sleep and circadian research. In addition, we sought to evaluate seasonal variations in a previously published dataset of 72 participants investigating circadian and sleep effects of evening light exposure in a laboratory protocol where daytime light history was not controlled. In this study, we selectively modulated melanopic irradiance at four different light levels (<90 lx). Here, we aimed to retrospectively evaluate seasonal variations in the responsiveness of the melanopsin system by combining all data sets in an exploratory manner. Our analyses suggest that light sensitivity is indeed reduced in summer compared to winter. Thus, to increase the reproducibility of NIF effects on sleep and circadian measures, we recommend an assessment of the light history and encourage standardization of reporting guidelines on the seasonal distribution of measurements.

Influence of the Human Field of View on Visual and Non-Visual Quantities in Indoor Environments

The visual and non-visual effectiveness of light is often determined by measuring the spectrally weighed irradiance on the corneal plane. This is typically achieved using spectral irradiance or illuminance measurements, captured in a hemispheric (2π) geometry with a diffuser. However, the human binocular field of view (FOV) is not a perfect hemisphere, as it is occluded both upward and downward. Previous research on FOV-restricted measurements is limited, leaving the error from using hemispheric measurements for non-visual quantities undefined. In our study, we tackled this issue by designing and 3D printing FOV occlusions as attachments to spectral measurement devices. We took measurements with and without the occlusion in various laboratory (light from different directions) and real-world lighting situations (light typically from above). Our findings reveal a reduction of visual and melanopic values due to the FOV occlusion. These ranged from negligible to more than 60% in realistic scenarios. Interestingly, the reduction was consistent for both visual and melanopic parameters, as the distribution of light in the FOV was generally spectrally homogeneous. An exception occurred in a specific artificial laboratory situation, where the melanopic daylight (D65) efficacy ratio changed by more than a factor of 2 solely because of the FOV occlusion. Additionally, we observed that head orientation had a marked effect on all quantities measured. In conclusion, our results highlight the potential for substantial errors when solely relying on vertical, hemispheric measurements in experiments and non-visual lighting design projects. We encourage the (additional) use of FOV occlusion in eye-level measurements for typical viewing directions, and we are providing open-source 3D-print files to facilitate this practice.

Hilaire MA, Lockley SW, Rahman SA. Supplementation of ambient lighting with a task lamp improves daytime alertness and cognitive performance in sleep-restricted individuals

STUDY OBJECTIVES

We examined the impact of adding a single-high-melanopic-illuminance task lamp in an otherwise low-melanopic-illuminance environment on alertness, neurobehavioral performance, learning, and mood during an 8-h simulated workday.

METHODS

Sixteen healthy young adults [mean(±SD) age = 24.2 ± 2.9, 8F] participated in a 3-day inpatient study with two 8-h simulated workdays and were randomized to either ambient fluorescent room light (~30 melanopic EDI lux, 50 lux), or room light supplemented with a light emitting diode task lamp (~250 melanopic EDI lux, 210 lux) in a cross-over design. Alertness, mood, and cognitive performance were assessed throughout the light exposure and compared between conditions using linear mixed models.

RESULTS

The primary outcome measure of percentage correct responses on the addition task was significantly improved relative to baseline in the supplemented condition (3.15% ± 1.18%), compared to the ambient conditions (0.93% ± 1.1%; FDR-adj q = 0.005). Additionally, reaction time and attentional failures on the psychomotor vigilance tasks were significantly improved with exposure to supplemented compared to ambient lighting (all, FDR-adj q ≤ 0.030). Furthermore, subjective measures of sleepiness, alertness, happiness, health, mood, and motivation were also significantly better in the supplemented, compared to ambient conditions (all, FDR-adj q ≤ 0.036). There was no difference in mood disturbance, affect, declarative memory, or motor learning between the conditions (all, FDR-adj q ≥ 0.308).

CONCLUSIONS

Our results show that supplementing ambient lighting with a high-melanopic-illuminance task lamp can improve daytime alertness and cognition. Therefore, high-melanopic-illuminance task lighting may be effective when incorporated into existing suboptimal lighting environments.

CLINICAL TRIALS

NCT04745312. Effect of Lighting Supplementation on Daytime Cognition. https://clinicaltrials.gov/ct2/show/NCT04745312.

S-Cone Photoreceptors Regulate Daily Rhythms and Light-Induced Arousal/Wakefulness in Diurnal Grass Rats (Arvicanthis niloticus)

Beyond visual perception, light has non-image-forming effects mediated by melanopsin-expressing, intrinsically photosensitive retinal ganglion cells (ipRGCs). The present study first used multielectrode array recordings to show that in a diurnal rodent, Nile grass rats (Arvicanthis niloticus), ipRGCs generate rod/cone-driven and melanopsin-based photoresponses that stably encode irradiance. Subsequently, two ipRGC-mediated non-image-forming effects, namely entrainment of daily rhythms and light-induced arousal, were examined. Animals were first housed under a 12:12 h light/dark cycle (lights-on at 0600 h) with the light phase generated by a low-irradiance fluorescent light (F12), a daylight spectrum (D65) stimulating all photoreceptors, or a narrowband 480 nm spectrum (480) that maximized melanopsin stimulation and minimized S-cone stimulation (λmax 360 nm) compared to D65. Daily rhythms of locomotor activities showed onset and offset closer to lights-on and lights-off, respectively, in D65 and 480 than in F12, and higher day/night activity ratio under D65 versus 480 and F12, suggesting the importance of S-cone stimulation. To assess light-induced arousal, 3-h light exposures using 4 spectra that stimulated melanopsin equally but S-cones differentially were superimposed on F12 background lighting: D65, 480, 480 + 365 (narrowband 365 nm), and D65 - 365. Compared to the F12-only condition, all four pulses increased in-cage activity and promoted wakefulness, with 480 + 365 having the greatest and longest-lasting wakefulness-promoting effects, again indicating the importance of stimulating S-cones as well as melanopsin. These findings provide insights into the temporal dynamics of photoreceptor contributions to non-image-forming photoresponses in a diurnal rodent that may help guide future studies of lighting environments and phototherapy protocols that promote human health and productivity.

A review on indoor environmental quality in sports facilities: Indoor air quality and ventilation during a pandemic

Because of COVID-19, the indoor environmental quality (IEQ) in sports facilities has been a concern to environmental health practitioners. To develop an overall understanding of the available guidelines and standards and studies performed on IEQ in sports facilities, an extensive literature study was conducted, with the aim of identifying: (1) indicators that are being used to assess IEQ in different sports facilities; (2) indicators that are potentially interesting to be used to assess indoor air, in particular; (3) gaps in knowledge to determine whether sports facilities are safe, healthy and comfortable for people to stay and perform their activities. The outcome indicates that most current standards and previous investigations on IEQ in sports facilities mainly focused on dose-related indicators (such as ventilation rate), while building-related indicators (such as ventilation regime) and occupant-related indicators (such as IEQ preferences) were rarely considered. Little attention is given to the fact that ventilation systems may play an important role in the air quality of the location, and few investigations have been performed on the transmission of SARS-CoV-2. This study recommends more research into both occupant and building-related indicators as well as cross-modal effects between various IEQ factors for developing future standards on sports facilities.

Disturbances of Hormonal Circadian Rhythms by Light Pollution

The circadian rhythms evolved to anticipate and cope with cyclic changes in environmental conditions. This adaptive function is currently compromised by increasing levels of artificial light at night (ALAN), which can represent a risk for the development of diseases of civilisation. The causal links are not completely understood, and this featured review focuses on the chronodisruption of the neuroendocrine control of physiology and behaviour by dim ALAN. The published data indicate that low levels of ALAN (2-5 lux) can attenuate the molecular mechanisms generating circadian rhythms in the central oscillator, eliminate the rhythmic changes in dominant hormonal signals, such as melatonin, testosterone and vasopressin, and interfere with the circadian rhythm of the dominant glucocorticoid corticosterone in rodents. These changes are associated with a disturbed daily pattern of metabolic changes and behavioural rhythms in activity and food and water intake. The increasing levels of ALAN require the identification of the pathways mediating possible negative consequences on health to design effective mitigation strategies to eliminate or minimise the effects of light pollution.

The Impact of Different Color Temperatures and Sources of Light on Mood and Vision: Acuity and Color Recognition

Background: Light is a physical factor that can influence the mood and vision of people during work and study. According to the importance of these physical factors, the present study aimed to investigate the effect of the source and color temperature on the mood and vision (acuity and color recognition) of students of TUMS and USWR medical universities. Methods: The present study is an applied study, and the research method is quasi-experimental. Twenty subjects were determined by first-type error (0.05) and test power (0.08). The mood was measured using the profile of mood states (POMS), visual acuity in different lighting conditions based on Snellen and FrACT methods, and color recognition by Ishihara’s test. Data were analyzed by SPSS 22, one-way ANOVA, and Greenhouse-Geisser. Results: The results of investigating six subscales of the POMS scale in sunlight, LED, and fluorescent with color temperatures of 4000 K and 3000 K indicated improvement in mood states (P < 0.001). Color recognition under different lighting conditions showed no significant difference (P < 0.05). However, visual acuity with the FrACT method under sunlight showed a significant difference in other lighting conditions (P < 0.001). Conclusions: Light sources can influence mood and vision states (acuity and color recognition) under different lighting conditions. Therefore, using sunlight in educational environments can improve the mood and state of students.

Blue Light-Ocular and Systemic Damaging Effects: A Narrative Review

Light is a fundamental aspect of our lives, being involved in the regulation of numerous processes in our body. While blue light has always existed in nature, with the ever-growing number of electronic devices that make use of short wavelength (blue) light, the human retina has seen increased exposure to it. Because it is at the high-energy end of the visible spectrum, many authors have investigated the theoretical harmful effects that it poses to the human retina and, more recently, the human body, given the discovery and characterization of the intrinsically photosensitive retinal ganglion cells. Many approaches have been explored, with the focus shifting throughout the years from examining classic ophthalmological parameters, such as visual acuity, and contrast sensitivity to more complex ones seen on electrophysiological assays and optical coherence tomographies. The current study aims to gather the most recent relevant data, reveal encountered pitfalls, and suggest future directions for studies regarding local and/or systemic effects of blue light retinal exposures.

The Rapid and International Expansion of Veterinary Clinical Skills Laboratories: A Survey to Establish Recent Developments

Veterinary clinical skills laboratories are used for teaching a wide range of practical, clinical, and surgical skills on models and simulators. A survey conducted in 2015 identified the role of such facilities in veterinary education in North America and Europe. The current study aimed to capture recent changes using a similar survey with three sections to collect data about the structure of the facility, its uses in teaching and assessment, and the staffing. The survey consisted of multiple choice and free text questions, was administered online using Qualtrics and was disseminated in 2021 via clinical skills networks and Associate Deans. Responses were received from 91 veterinary colleges in 34 countries; 68 had an existing clinical skills laboratory and 23 were planning to open one within 1-2 years. Collated information from the quantitative data described the facility, teaching, assessment and staffing. Major themes emerged from the qualitative data relating to aspects of the layout, location, integration in the curriculum, contributions to student learning, and the team managing and supporting the facility. Challenges were associated with budgeting, the ongoing need for expansion and leadership of the program. In summary, veterinary clinical skills laboratories are increasingly common around the world and the contributions to student learning and animal welfare were well recognized. The information about existing and planned laboratories and the tips from those managing the facilities provides valuable guidance for anyone intending to open or expand an existing clinical skills laboratory.

Multilayered optofluidics for sustainable buildings

Indoor climate control is among the most energy-intensive activities conducted by humans. A building facade that can achieve versatile climate control directly, through independent and multifunctional optical reconfigurations, could significantly reduce this energy footprint, and its development represents a pertinent unmet challenge toward global sustainability. Drawing from optically adaptive multilayer skins within biological organisms, we report a multilayered millifluidic interface for achieving a comprehensive suite of independent optical responses in buildings. We digitally control the flow of aqueous solutions within confined milliscale channels, demonstrating independent command over total transmitted light intensity (95% modulation between 250 and 2,500 nm), near-infrared-selective absorption (70% modulation between 740 and 2,500 nm), and dispersion (scattering). This combinatorial optical tunability enables configurable optimization of the amount, wavelength, and position of transmitted solar radiation within buildings over time, resulting in annual modeled energy reductions of more than 43% over existing technologies. Our scalable "optofluidic" platform, leveraging a versatile range of aqueous chemistries, may represent a general solution for the climate control of buildings.

Circadian phase advances in children during camping life according to the natural light-dark cycle

BACKGROUND

It is known that the circadian rhythm phase in adults can be advanced in a natural light-dark cycle without electrical lighting. However, the effect of advanced sleep-wake timing according to the natural light-dark cycle on children's circadian phase is unclear. We investigated the effects of approximately 2 weeks of camping life with little access to artificial lighting on children's circadian phases. We also conducted an exploratory examination on the effects of wake time according to natural sunrise time on the manner of the advance of their circadian phases.

METHODS

Twenty-one healthy children (mean ± SD age, 10.6 ± 1.4 years) participated in a camping program with wake time (4:00) being earlier than sunrise time (EW condition), and 21 healthy children (10.4 ± 1.1 years) participated in a camping program with wake time (5:00) being almost matched to sunrise time (SW condition). Salivary dim light melatonin onset (DLMO) before the camping program and that after approximately 2 weeks of camping were compared.

RESULTS

DLMO was advanced by approximately 2 h after the camping program compared with the circadian phase in daily life in both conditions. In addition, the advances in DLMO were significantly correlated with mid-sleep points before the camp in both conditions (EW: r = 0.72, p < 0.01, SW: r = 0.70, p < 0.01). These correlations mean that the phase advance was greater for the children with delayed sleep habits in daily life. Furthermore, in the EW condition, mean DLMO after the camp (18:09 ± 0:33 h) was earlier than natural sunset time and there was no significant decrease in interindividual variability in DLMO. On the other hand, in the SW condition, mean DLMO after the camp (18:43 ± 0:20 h) matched natural sunset time and interindividual variability in DLMO was significantly lower than that before the camp.

CONCLUSIONS

Camping with advanced sleep and wake timing under natural sunlight advances children's circadian phases. However, DLMO earlier than sunset in an early waking condition may lead to large interindividual variability in the circadian rhythm phase.

Melatonin suppression does not automatically alter sleepiness, vigilance, sensory processing, or sleep

Presleep exposure to short-wavelength light suppresses melatonin and decreases sleepiness with activating effects extending to sleep. This has mainly been attributed to melanopic effects, but mechanistic insights are missing. Thus, we investigated whether two light conditions only differing in the melanopic effects (123 vs. 59 lx melanopic EDI) differentially affect sleep besides melatonin. Additionally, we studied whether the light differentially modulates sensory processing during wakefulness and sleep. Twenty-nine healthy volunteers (18-30 years, 15 women) were exposed to two metameric light conditions (high- vs. low-melanopic, ≈60 photopic lx) for 1 h ending 50 min prior to habitual bed time. This was followed by an 8-h sleep opportunity with polysomnography. Objective sleep measurements were complemented by self-report. Salivary melatonin, subjective sleepiness, and behavioral vigilance were sampled at regular intervals. Sensory processing was evaluated during light exposure and sleep on the basis of neural responses related to violations of expectations in an oddball paradigm. We observed suppression of melatonin by ≈14% in the high- compared to the low-melanopic condition. However, conditions did not differentially affect sleep, sleep quality, sleepiness, or vigilance. A neural mismatch response was evident during all sleep stages, but not differentially modulated by light. Suppression of melatonin by light targeting the melanopic system does not automatically translate to acutely altered levels of vigilance or sleepiness or to changes in sleep, sleep quality, or basic sensory processing. Given contradicting earlier findings and the retinal anatomy, this may suggest that an interaction between melanopsin and cone-rod signals needs to be considered. Clinical Trial Registry: German Clinical Trials Register, DRKS00023602, https://www.drks.de/drks_web/navigate.do?navigationId=trial.HTML&TRIAL_ID=DRKS00023602.

Human circadian rhythm studies: Practical guidelines for inclusion/exclusion criteria and protocol

As interest in circadian rhythms and their effects continues to grow, there is an increasing need to perform circadian studies in humans. Although the constant routine is the gold standard for these studies, there are advantages to performing more naturalistic studies. Here, a review of protocols for such studies is provided along with sample inclusion and exclusion criteria. Sleep routines, drug use, shift work, and menstrual cycle are addressed as screening considerations. Regarding protocol, best practices for measuring melatonin, including light settings, posture, exercise, and dietary habits are described. The inclusion/exclusion recommendations and protocol guidelines are intended to reduce confounding variables in studies that do not involve the constant routine. Given practical limitations, a range of recommendations is provided from stringent to lenient. The scientific rationale behind these recommendations is discussed. However, where the science is equivocal, recommendations are based on empirical decisions made in previous studies. While not all of the recommendations listed may be practical in all research settings and with limited potential participants, the goal is to allow investigators to make well informed decisions about their screening procedures and protocol techniques and to improve rigor and reproducibility, in line with the objectives of the National Institutes of Health.

Effects of dynamic lighting on circadian phase, self-reported sleep and performance during a 45-day space analog mission with chronic variable sleep deficiency

Spaceflight exposes crewmembers to circadian misalignment and sleep loss, which impair cognition and increase the risk of errors and accidents. We compared the effects of an experimental dynamic lighting schedule (DLS) with a standard static lighting schedule (SLS) on circadian phase, self-reported sleep and cognition during a 45-day simulated space mission. Sixteen participants (mean age [±SD] 37.4 ± 6.7 years; 5 F; n = 8/lighting condition) were studied in four-person teams at the NASA Human Exploration Research Analog. Participants were scheduled to sleep 8 h/night on two weekend nights, 5 h/night on five weekday nights, repeated for six 7-day cycles, with scheduled waketime fixed at 7:00 a.m. Compared to the SLS where illuminance and spectrum remained constant during wake (~4000K), DLS increased the illuminance and short-wavelength (blue) content of white light (~6000K) approximately threefold in the main workspace (Level 1), until 3 h before bedtime when illuminance was reduced by ~96% and the blue content also reduced throughout (~4000K × 2 h, ~3000K × 1 h) until bedtime. The average (±SE) urinary 6-sulphatoxymelatonin (aMT6s) acrophase time was significantly later in the SLS (6.22 ± 0.34 h) compared to the DLS (4.76 ± 0.53 h) and more variable in SLS compared to DLS (37.2 ± 3.6 min vs. 28.2 ± 2.4 min, respectively, p = .04). Compared to DLS, self-reported sleep was more frequently misaligned relative to circadian phase in SLS RR: 6.75, 95% CI 1.55-29.36, p = .01), but neither self-reported sleep duration nor latency to sleep was different between lighting conditions. Accuracy in the abstract matching and matrix reasoning tests were significantly better in DLS compared to SLS (false discovery rate-adjusted p ≤ .04). Overall, DLS alleviated the drift in circadian phase typically observed in space analog studies and reduced the prevalence of self-reported sleep episodes occurring at an adverse circadian phase. Our results support incorporating DLS in future missions, which may facilitate appropriate circadian alignment and reduce the risk of sleep disruption.

Rise and shine: The use of polychromatic short-wavelength-enriched light to mitigate sleep inertia at night following awakening from slow-wave sleep

Sleep inertia is the brief period of performance impairment and reduced alertness experienced after waking, especially from slow-wave sleep. We assessed the efficacy of polychromatic short-wavelength-enriched light to improve vigilant attention, alertness and mood immediately after waking from slow-wave sleep at night. Twelve participants (six female, 23.3 ± 4.2 years) maintained an actigraphy-confirmed sleep schedule of 8.5 hr for 5 nights, and 5 hr for 1 night prior to an overnight laboratory visit. In the laboratory, participants were awakened from slow-wave sleep, and immediately exposed to either dim, red ambient light (control) or polychromatic short-wavelength-enriched light (light) for 1 hr in a randomized crossover design. They completed a 5-min Psychomotor Vigilance Task, the Karolinska Sleepiness Scale, and Visual Analogue Scales of mood at 2, 17, 32 and 47 min after waking. Following this testing period, lights were turned off and participants returned to sleep. They were awakened from their subsequent slow-wave sleep period and received the opposite condition. Compared with the control condition, participants exposed to light had fewer Psychomotor Vigilance Task lapses (χ² [1] = 5.285, p = 0.022), reported feeling more alert (Karolinska Sleepiness Scale: F_1,77  = 4.955, p = 0.029; Visual Analogue Scale_alert : F_1,77  = 8.226, p = 0.005), and reported improved mood (Visual Analogue Scale_cheerful : F_1,77  = 8.615, p = 0.004). There was no significant difference in sleep-onset latency between conditions following the testing period (t₁₀  = 1.024, p = 0.330). Our results suggest that exposure to polychromatic short-wavelength-enriched light immediately after waking from slow-wave sleep at night may help improve vigilant attention, subjective alertness, and mood. Future studies should explore the potential mechanisms of this countermeasure and its efficacy in real-world environments.

Alerting effects of light in healthy individuals: a systematic review and meta-analysis

Light plays an essential role in psychobiological and psychophysiological processes, such as alertness. The alerting effect is influenced by light characteristics and the timing of interventions. This meta-analysis is the first to systematically review the effect of light intervention on alertness and to discuss the optimal protocol for light intervention. In this meta-analysis, registered at PROSPERO (Registration ID: CRD42020181485), we conducted a systematic search of the Web of Science, PubMed, and PsycINFO databases for studies published in English prior to August 2021. The outcomes included both subjective and objective alertness. Subgroup analyses considered a variety of factors, such as wavelength, correlated color temperature (CCT), light illuminance, and timing of interventions (daytime, night-time, or all day). Twenty-seven crossover studies and two parallel-group studies were included in this meta-analysis, with a total of 1210 healthy participants (636 (52%) male, mean age 25.62 years). The results revealed that light intervention had a positive effect on both subjective alertness (standardized mean difference (SMD) = –0.28, 95% confidence interval (CI): –0.49 to –0.06, P = 0.01) and objective alertness in healthy subjects (SMD = –0.34, 95% CI: –0.68 to –0.01, P = 0.04). The subgroup analysis revealed that cold light was better than warm light in improving subjective alertness (SMD = –0.37, 95% CI: –0.65 to –0.10, P = 0.007, I² = 26%) and objective alertness (SMD = –0.36, 95% CI: –0.66 to –0.07, P = 0.02, I² = 0). Both daytime (SMD = –0.22, 95% CI: –0.37 to –0.07, P = 0.005, I² = 74%) and night-time (SMD = –0.32, 95% CI: –0.61 to –0.02, P = 0.04, I² = 0) light exposure improved subjective alertness. The results of this meta-analysis and systematic review indicate that light exposure is associated with significant improvement in subjective and objective alertness. In addition, light exposure with a higher CCT was more effective in improving alertness than light exposure with a lower CCT. Our results also suggest that both daytime and night-time light exposure can improve subjective alertness.

Experimental Study: Children's Perceptions Expressed Through Drawings and Coloring

A large body of literature has addressed processes underlying human perception, with some assertions that children do not perceive space or colors in the same way as adults. Since children express themselves easily and acquire knowledge through graphic symbols, when determining psycho-motor maturity and perceptions of a preschool aged children, observers must evaluate their use of non-verbal graphics. Thus, we used young children's drawings to examine their use of color and spatial perception, as well as to identify differences between children in rural and urban communities. Of 94 participants from rural and urban communities, 46 were kindergarten aged (5.5-6.5 years), and 48 were preschool aged (4.5-5.5 years). Comparing children from urban and rural areas, there were significant differences in their perception of different colors and spatial relations. Motor abilities were significantly different between children of different ages and gender. We argue that the applied assessment methods, such as children's drawings, could be a basis for measuring effective learning and practicing of children's abilities as expressed in the classroom, and that tools may be useful for creating individualized educational plans and programs for developing children's skills through play.

A review of the current state of research on artificial blue light safety as it applies to digital devices

Light is necessary for human health and well-being. As we spend more time indoors, we are being increasingly exposed to artificial light. The development of artificial lighting has allowed us to control the brightness, colour, and timing of our light exposure. Yet, the widespread use of artificial light has raised concerns about the impact of altering our light environment on our health. The widespread adoption of personal digital devices over the past decade has exposed us to yet another source of artificial light. We spend a significant amount of time using digital devices with light-emitting screens, including smartphones and tablets, at close range. The light emitted from these devices, while appearing white, has an emission spectrum with a peak in the blue range. Blue light is often characterised as hazardous as its photon energy is higher than that of other wavelengths of visible light. Under certain conditions, visible blue light can cause harm to the retina and other ocular structures. Blue light can also influence the circadian rhythm and processes mediated by melanopsin-expressing intrinsically photosensitive retinal ganglion cells. While the blue component of sunlight is necessary for various physiological processes, whether the low-illuminance artificial blue light emitted from digital devices presents a risk to our health remains an ongoing area of debate. As technological advancements continue, it is relevant to understand how new devices may influence our well-being. This review examines the existing research on artificial blue light safety and the eye, visual performance, and circadian functions.

The Effect of Correlated Colour Temperature on Physiological, Emotional and Subjective Satisfaction in the Hygiene Area of a Space Station

The hygiene area is one of the most important facilities in a space station. If its environmental lighting is appropriately designed, it can significantly reduce the psychological pressure on astronauts. This study investigates the effect of correlated colour temperature (CCT) on heart rate, galvanic skin response, emotion and satisfaction in the hygiene area of a space station. Forty subjects participated in experiments in a hygiene area simulator with a controlled lighting environment. The lighting conditions included 2700 K, 3300 K, 3600 K, 5000 K and 6300 K; physiological responses (heart rate, galvanic skin response), as well as emotion and satisfaction, were recorded. The results showed that CCT significantly influenced the participants’ physiological and subjective responses in the space station hygiene area. 6300 K led to the best emotion and satisfaction levels, the highest galvanic skin response and the lowest heart rate. The opposite was true for 2700 K.

The Long-Term Effect of Blue-Light Blocking Spectacle Lenses on Adults’ Contrast Perception

Purpose

To evaluate the long-term effect of two different degrees of blue-light blocking (BB) spectacle lenses on adults’ contrast perception under various lighting conditions.

Methods

In total, 144 healthy adults aged 24.70 (±4.32 years) were recruited to this randomized controlled trial. The participants were randomly divided into three groups and used three different spectacle lenses (15% BB: 15% blue-blocking spectacle lenses; 30% BB: 30% blue-blocking spectacle lenses; RC: regular clear lenses serving as control). Contrast sensitivity under four light conditions (scotopic and photopic, both with/without glare) was measured using standard clinical tests at baseline, 1 month, 3 months and 6 months of use. The area under the log contrast sensitivity function (AULCSF) was also computed as an index for their overall contrast sensitivity across spatial frequencies.

Results

There was no significant difference in AULCSFs among the three types of spectacle lenses under any light condition (all P > 0.81). No statistical difference was found in the AULSCF among the four time points (all P > 0.39), with no interaction between the effects of group and time (all P > 0.42).

Conclusion

Wearing blue-light blocking lens had no clinically significant effect on adults’ long-term contrast perception under scotopic or photopic conditions, or with glare.

Impact of Upgraded Lighting on Falls in Care Home Residents

OBJECTIVES

Falls in care home residents have major health and economic implications. Given the impact of lighting on visual acuity, alertness, and sleep and their potential influence on falls, we aimed to assess the impact of upgraded lighting on the rate of falls in long-term care home residents.

DESIGN

An observational study of 2 pairs of care homes (4 sites total). One site from each pair was selected for solid-state lighting upgrade, and the other site served as a control.

SETTING AND PARTICIPANTS

Two pairs of care homes with 758 residents (126,479 resident-days; mean age (±SD) 81.0 ± 11.7 years; 57% female; 31% with dementia).

METHODS

One "experimental" site from each pair had solid-state lighting installed throughout the facility that changed in intensity and spectrum to increase short-wavelength (blue light) exposure during the day (6 am-6 pm) and decrease it overnight (6 pm-6 am). The control sites retained standard lighting with no change in intensity or spectrum throughout the day. The number of falls aggregated from medical records were assessed over an approximately 24-month interval. The primary comparison between the sites was the rate of falls per 1000 resident-days.

RESULTS

Before the lighting upgrade, the rate of falls was similar between experimental and control sites (6.94 vs 6.62 falls per 1000 resident-days, respectively; rate ratio [RR] 1.05; 95% CI 0.70-1.58; P = .82). Following the upgrade, falls were reduced by 43% at experimental sites compared with control sites (4.82 vs 8.44 falls per 1000 resident-days, respectively; RR 0.57; 95% CI 0.39-0.84; P = .004).

CONCLUSIONS AND IMPLICATIONS

Upgrading ambient lighting to incorporate higher intensity blue-enriched white light during the daytime and lower intensity overnight represents an effective, passive, low-cost, low-burden addition to current preventive strategies to reduce fall risk in long-term care settings.

Dynamic ensemble prediction of cognitive performance in spaceflight

During spaceflight, astronauts face a unique set of stressors, including microgravity, isolation, and confinement, as well as environmental and operational hazards. These factors can negatively impact sleep, alertness, and neurobehavioral performance, all of which are critical to mission success. In this paper, we predict neurobehavioral performance over the course of a 6-month mission aboard the International Space Station (ISS), using ISS environmental data as well as self-reported and cognitive data collected longitudinally from 24 astronauts. Neurobehavioral performance was repeatedly assessed via a 3-min Psychomotor Vigilance Test (PVT-B) that is highly sensitive to the effects of sleep deprivation. To relate PVT-B performance to time-varying and discordantly-measured environmental, operational, and psychological covariates, we propose an ensemble prediction model comprising of linear mixed effects, random forest, and functional concurrent models. An extensive cross-validation procedure reveals that this ensemble outperforms any one of its components alone. We also identify the most important predictors of PVT-B performance, which include an individual's previous PVT-B performance, reported fatigue and stress, and temperature and radiation dose. This method is broadly applicable to settings where the main goal is accurate, individualized prediction of human behavior involving a mixture of person-level traits and irregularly measured time series.

The Common Effects of Sleep Deprivation on Human Long-Term Memory and Cognitive Control Processes

Sleep deprivation is known to have adverse effects on various cognitive abilities. In particular, a lack of sleep has been reported to disrupt memory consolidation and cognitive control functions. Here, focusing on long-term memory and cognitive control processes, we review the consistency and reliability of the results of previous studies of sleep deprivation effects on behavioral performance with variations in the types of stimuli and tasks. Moreover, we examine neural response changes related to these behavioral changes induced by sleep deprivation based on human fMRI studies to determine the brain regions in which neural responses increase or decrease as a consequence of sleep deprivation. Additionally, we discuss about the possibility that light as an environmentally influential factor affects our sleep cycles and related cognitive processes.

Research on the Application of the Dynamic Assisted Sleep Light to Smart Mobile Devices

With the rapid development of science and technology, social competition becomes more and more fierce, and work pressure becomes more and more intense. The problem of sleep has become a disease of modern civilization, and in order to alleviate sleep problems and improve sleep quality, related research methods are constantly updated, and there are more and more ways to address these problems. In this paper, we propose a dynamic assisted sleep light that adjusts the color temperature, illuminance, and frequency of change by controlling the backlight of the smart mobile device, so that the user experiences an improved quality of sleep. In this study, the methods of subjective questionnaire survey and non-subjective physiological parameter measurement were adopted for analysis. The results showed that the continuous use of the light source could continuously enhance the user’s delta energy during sleep and promote the improvement of sleep quality.

Cross-sectional study of intraocular cataract lens replacement, circadian rest–activity rhythms, and sleep quality in older adults

Study Objectives

Age-related cataract decreases light transmission at the most sensitive spectrum for circadian photoentrainment, with negative ramifications for human health. Here, we assessed whether intraocular lens replacement (IOL) in older patients with previous cataract was associated with increased stability and amplitude of circadian rest–activity rhythms, and improved sleep quality.

Methods

Our cross-sectional study included sixteen healthy older individuals without ocular diseases (controls; 55–80 years; 63.6 ± 5.6y; 8 women) and 13 patients with previous cataract and bilateral IOL (eight with blue-blocking [BB] lens and five with ultraviolet-only [UV] blocking lens; 55–80 years; 69.9 ± 5.2y; 9 women). The study comprised three weeks of at home rest–activity assessments using wrist-worn actigraphs, and each week preceded a laboratory protocol. Primary outcomes were actigraphy-derived interdaily stability, intradaily variability, and relative amplitude of circadian rest–activity rhythms. Secondary outcomes were actigraphy-assessed sleep quality (i.e. time in bed, sleep duration, sleep efficiency, mean wake bout time and fragmentation index).

Results

Patients with IOL had significantly higher interdaily stability (“Group” effect: pFDR =.001), but not intradaily variability (“Group” effect: pFDR = n.s.), and significantly higher relative amplitude of rest–activity rhythms (“Group” effect: pFDR &lt; .001). Moreover, patients with IOL had significantly higher activity levels during the day and lower levels during the evening, as compared to healthy older controls (“Group” effect: pFDR = .03). Analyses of actigraphy-derived sleep parameters yielded no significant differences across groups (“Group” effect: all pFDR &gt; .1).

Conclusions

Our cross-sectional study suggests that enhancing spectral lens transmission in patients with cataract may benefit their circadian health.

The role of melanopsin photoreception on visual attention linked pupil responses

A decision during a visual task is marked by a task‐evoked pupil dilation (TEPD) that is linked to the global cortical arousal state. Melanopsin expressing intrinsically photosensitive retinal ganglion cells (ipRGCs) form the afferent pathway for this pupil response. Melanopsin activation also influences mood and arousal and increases activity in decision‐making brain areas that receive direct ipRGC projections. Here, an optical photostimulation method controlled the excitations of all five photoreceptor classes in the human eye to isolate melanopsin‐mediated photoreception. We hypothesised that the TEPD can be driven by directing active visual covert attention through the ipRGC pathway. When observers are completely certain of the stimulus presence, melanopsin‐directed stimulation produces a TEPD of similar amplitude to a cone‐directed stimulation, with their combination producing larger amplitudes. This dilation is satisfactorily modelled by linear addition with a higher melanopsin weighting in ipRGCs. Visual reaction times were longest in response to melanopsin‐directed lights. Next, we asked whether the afferent photoreceptor input and decision certainty, controlled by priming the observer's a priori expectation, interact to drive the TEPD. Signal detection analysis showed that by fixing the predecision certainty (bias), the phasic arousal and TEPD amplitude vary with observer criterion (c′) and sensitivity (d′) but not with preferential activation of melanopsin. The signature feature of the melanopsin response during attention was a biphasic TEPD. We conclude that active covert attention can be modulated by visual information mediated via ipRGCs, but that phasic arousal responses marked using the TEPD are not increased by higher levels of melanopsin activation.

Recommendations for daytime, evening, and nighttime indoor light exposure to best support physiology, sleep, and wakefulness in healthy adults

Ocular light exposure has important influences on human health and well-being through modulation of circadian rhythms and sleep, as well as neuroendocrine and cognitive functions. Prevailing patterns of light exposure do not optimally engage these actions for many individuals, but advances in our understanding of the underpinning mechanisms and emerging lighting technologies now present opportunities to adjust lighting to promote optimal physical and mental health and performance. A newly developed, international standard provides a SI-compliant way of quantifying the influence of light on the intrinsically photosensitive, melanopsin-expressing, retinal neurons that mediate these effects. The present report provides recommendations for lighting, based on an expert scientific consensus and expressed in an easily measured quantity (melanopic equivalent daylight illuminance (melaponic EDI)) defined within this standard. The recommendations are supported by detailed analysis of the sensitivity of human circadian, neuroendocrine, and alerting responses to ocular light and provide a straightforward framework to inform lighting design and practice.

Influence of Wearing Blue Lenses on Melatonin Production and Performance in Volleyball Players

We analyzed the effects of wearing blue lenses on melatonin level, physical and cognitive performance. Fifteen youth volleyball players (15.0±1.5 yrs) attended the laboratory on 3 occasions (48-h interval): on the 1 ^st visit they were familiarized with the procedures of the study, and on 2 ^nd and 3 ^rd visits they were submitted to the testing protocol wearing transparent (control) or blue lens glasses in a counterbalanced crossover design. The protocol consisted of 10 min in “total darkness,” 30 min of light stimulation (wearing blue or transparent lenses), followed by an attentional test, and an agility T-test (without wearing the glasses). Samples of saliva (to determine melatonin concentration) were obtained pre- and post-exposure (30 min) to artificial light, wearing the lenses. Sleepiness, alertness, attention, mood, and perceived recovery status and performance variables (reaction time and T-test) were assessed after lens exposure. Melatonin levels did not differ within and between groups (blue lenses, pre: 0.79±0.73 and post: 1.19±1.374 pg/dl, p=0.252, effect size (ES)=0.38; control, pre: 0.97±1.00 and post: 0.67±0.71 pg/dl, p=0.305, ES=–0.35). Nonetheless, melatonin differences were significantly correlated with physical sedation for glasses with blue lenses (r=−0.526; p=0.04). No other variables differed (p>0.05) between protocols, including T-test performance (p=0.07; ES=0.41). Blue lenses do not influence melatonin levels, cognitive/physical performance, and mood status in amateur youth volleyball players.

Social, Biological and Behavioral Factors Associated with Social Jet Lag and Sleep Duration in University Students from a Low Urbanized City

Introduction

Sleep deprivation and social jet lag are observed in college students from highly urbanized cities. However, does these consequences also present in college students from a low urbanization city?

Objective

To evaluate the prevalence and social, biological and behavioral factors associated with sleep deprivation and social jet lag in university students from a low urbanized city of Brazil.

Methods

A total of 298 university students participated in the study through application of the Health and Sleep and the Munich Chronotype Questionnaires. Multiple linear regression with stepwise-forward method was adopted to assess the associations of the factors with the outcome variables.

Results

Doing leisure activities (LA) (B = 23.24) and academic demand (AD) before bedtime (B = 19.51), both on the weekend, and doing household chores (HC) before bedtime (B = 17.61) in the week were associated with an increase in social jet lag, while stimulating drinks (SD) were associated with a decrease (B = −15.17). Shorter sleep duration in the week was related to chronotype (B = −0.56), male (B = −26.51), doing LA (B = −27.63), poor perception about sleeping place (PPSP) (B = −43.02) and daily commute (B = −68.97). The shorter sleep duration in the weekend was associated to male (B = −36.36), PPSP (B = −58.16), have recreational and religious activities (B = −31.11), doing LA (B = −25.10) and AD (B = −23.60). Just chronotype was associated with longer sleep duration in the weekend (B = 0.25).

Conclusion

University students from a low urbanized city present social jet lag, shorter sleep duration on school days and longer sleep duration on free days as a result of biological and social factors, and mostly behavioral factors.

Characteristics of light pollution - A case study of Warsaw (Poland) and Fukuoka (Japan)

Artificial light has been present in human life for decades but our knowledge of its effects is still insufficient. Lighting lets us be active longer, gives us a sense of security and provides aesthetic experiences. Despite all of these advantages, in urban areas artificial light also has a negative effects on the environment and human life. Although light pollution is one of the most common forms of anthropogenic environmental change, this phenomenon remains insufficiently investigated. The present work thus focuses on night sky brightness and artificial factors impacting the level of the phenomenon using Warsaw (Poland) and Fukuoka (Japan) as an example. The basis of the study is the new World Atlas of Artificial Night Sky Brightness. Moreover, we used image data from the Visible Infrared Imaging Radiometer Suite Day/Night Band and data from field research to analyse the primary artificial light characteristics in the two cities: illumination, colour temperature, peak wavelength, dominant wavelength, stimulation of photoreceptors, design of lighting fixtures and radiance. The results indicate that Warsaw (area: 517.2 km²; population: 1 777 972) is characterized by higher light pollution than Fukuoka (area: 343.5 km²; population: 1 554 229). Skyglow is primarily influenced by the number of light sources; however, local differentiation of the phenomenon depends on the spectral characteristics and design of lighting fixtures. Moreover, environmental features may affect light pollution through scattering, reflection and absorption. Outdoor lighting in Warsaw was characterized by a higher value of light illumination and greater stimulation of photoreceptors sensitive to long and medium waves. However, the lighting infrastructure in Fukuoka was also unsuitable, as it was characterised by high values of colour temperature and stimulation of photoreceptors sensitive to short waves and ganglion cells, which may be detrimental to the human body.

Effects of Light on Attention and Reaction Time: A Systematic Review

BACKGROUND

Accuracy, speed, efficiency, and applicability of activities in the workplace are among the most important effective factors on people's productivity, which is in turn affected by environmental factors, such as light. Therefore, the present research aimed to review the studies performed about the effects of light on attention and reaction time.

METHODS

This review study systematically searched articles from 2000-2019 in databases of Google Scholar, ISC, SID, Magiran, Web of Science, Science Direct, PubMed, and Scopus using keywords of light, lighting, attention, and reaction time. The titles and abstracts of articles containing relevant results over the past 20 years were extracted. Thereafter, they were categorized and analyzed according to the title, author name, publication year, study method, study type, and evaluation results.

RESULTS

Based on the results, the light with shorter wavelengths, higher intensity, and higher color temperature led to suppressed melatonin, higher consciousness, less somnolence, increased attention, and faster reaction time. Simultaneous exposure to harmful levels of environmental factors affects cognitive and physiological parameters, acting independently with a separate mechanism or synergistically with a similar mechanism. The best light in the regulation of psychological, biological, and cognitive processes is bright daylight in the morning with a short wavelength, high intensity, and more lasting effects.

CONCLUSION

As evidenced by the obtained results,  light is a powerful modulator of non-visual performance in cognitive tasks. The wavelength, color temperature, and light intensity modulate brain responses to cognitive tasks, including attention and reaction time. Therefore, these parameters, along with personal and environmental factors, should be considered in designing and using light.

The Influence of Intraocular Lens Implantation and Alterations in Blue Light Transmittance Level on the Brain Functional Network Architecture Reorganization in Cataract Patients

BACKGROUND

Cataract is one of the most common age-related vision deteriorations, leading to opacification of the lens and therefore visual impairment as well as blindness. Both cataract extraction and the implantation of blue light filtering lens are believed to improve not only vision but also overall functioning.

METHODS

Thirty-four cataract patients were subject to resting-state functional magnetic resonance imaging before and after cataract extraction and intraocular lens implantation (IOL). Global and local graph metrics were calculated in order to investigate the reorganization of functional network architecture associated with alterations in blue light transmittance. Psychomotor vigilance task (PVT) was conducted.

RESULTS

Graph theory-based analysis revealed decreased eigenvector centrality after the cataract extraction and IOL replacement in inferior occipital gyrus, superior parietal gyrus and many cerebellum regions as well as increased clustering coefficient in superior and inferior parietal gyrus, middle temporal gyrus and various cerebellum regions. PVT results revealed significant change between experimental sessions as patients responded faster after IOL replacement. Moreover, a few regions were correlated with the difference in blue light transmittance and the time reaction in PVT.

CONCLUSION

Current study revealed substantial functional network architecture reorganization associated with cataract extraction and alteration in blue light transmittance.

Context dependence of head bobs in gerbils and potential neural contributions

Headbobs are up-down movements of the cranium associated with the use of motion parallax for depth perception. Mongolian gerbils (aka jirds; Meriones unguiculatus) often execute a series of headbobs prior to jumping between surfaces. Gerbils were tested in a jumping stand task and headbobs videotaped under three light levels approximating low daylight, dawn/dusk, and moonlight across a range of distances to target. Headbobs per trial increased linearly with increasing distance to the target platform, whereas headbob frequency (rate of headbobbing pre-jump on the start platform) increased with gap distance up to an intermediate level and then decreased. Overall, gerbils made the most headbobs per trial under the darkest conditions, whereas their headbobbing rate was highest for medium illumination, especially for medium-long gap distances. There was a positive correlation between headbob frequency and volume of the superior colliculus (SC), but no relationship between headbobs and relative size of the temporo-posterior (TP) visual cortex. The results suggest that gerbils employ a specific visuomotor strategy for depth perception differentially under different conditions. We suggest that the deployment of headbobs under specific conditions may be part of an SC-driven vigilant state, of which more rapid sampling of the visual environment using headbobs for depth estimation is one component. Moreover, the findings highlight the importance of considering ecological factors in designing studies of visual behavior and its underpinnings in rodents.

Development of a Home-Based Light Therapy for Fatigue Following Traumatic Brain Injury: Two Case Studies

Background and Objectives: Fatigue and sleep disturbance negatively impact quality of life following brain injury and there are no established treatments. Building on research showing efficacy of blue light therapy delivered via a lightbox in reducing fatigue and daytime sleepiness after traumatic brain injury (TBI), this paper describes the development and implementation of a novel in-home light therapy to alleviate fatigue and sleep disturbance in two case studies. Methods: During the 8-week lighting intervention, participants' home lighting was adjusted to provide high intensity, blue-enriched (high melanopic) light all day as a stimulant and dimmer, blue-depleted (low melanopic) light for 3 h before sleep as a soporific. The sham 8-week control condition resembled participants' usual (baseline) lighting conditions (3,000-4,000 K all day). Lighting conditions were crossed-over. Outcomes were measures of fatigue, subjective daytime sleepiness, sleep quality, insomnia symptoms, psychomotor vigilance and mood. Case study participants were a 35-year old male (5 years post-TBI), and a 46-year-old female (22 years post-TBI). Results: The relative proportion of melanopic lux was greater in Treatment lighting than Control during daytime, and lower during evenings. Participants found treatment to be feasible to implement, and was well-tolerated with no serious side effects noted. Self-reported compliance was >70%. Both cases demonstrated reduced fatigue, sleep disturbance and insomnia symptoms during the treatment lighting intervention. Case 2 additionally showed reductions in daytime sleepiness and depressive symptoms. As expected, symptoms trended toward baseline levels during the control condition. Discussion: Treatment was positively received and compliance rates were high, with no problematic side-effects. Participants expressed interest in continuing the ambient light therapy in their daily lives. Conclusions: These cases studies demonstrate the acceptability and feasibility of implementing a personalized in-home dynamic light treatment for TBI patients, with evidence for efficacy in reducing fatigue and sleep disturbance. Clinical Trial Registration:www.anzctr.org.au, identifier: ACTRN12617000866303.

Daily Morning Blue Light Therapy Improves Daytime Sleepiness, Sleep Quality, and Quality of Life Following a Mild Traumatic Brain Injury

OBJECTIVE

Identify the treatment effects of 6 weeks of daily 30-minute sessions of morning blue light therapy compared with placebo amber light therapy in the treatment of sleep disruption following mild traumatic brain injury.

DESIGN

Placebo-controlled randomized trial.

PARTICIPANTS

Adults aged 18 to 45 years with a mild traumatic brain injury within the past 18 months (n = 35).

MAIN OUTCOME MEASURES

Epworth Sleepiness Scale, Pittsburgh Sleep Quality Index, Beck Depression Inventory II, Rivermead Post-concussion Symptom Questionnaire, Functional Outcomes of Sleep Questionnaire, and actigraphy-derived sleep measures.

RESULTS

Following treatment, moderate to large improvements were observed with individuals in the blue light therapy group reporting lower Epworth Sleepiness Scale (Hedges' g = 0.882), Beck Depression Inventory II (g = 0.684), Rivermead Post-concussion Symptom Questionnaire chronic (g = 0.611), and somatic (g = 0.597) symptoms, and experiencing lower normalized wake after sleep onset (g = 0.667) than those in the amber light therapy group. In addition, individuals in the blue light therapy group experienced greater total sleep time (g = 0.529) and reported improved Functional Outcomes of Sleep Questionnaire scores (g = 0.929) than those in the amber light therapy group.

CONCLUSION

Daytime sleepiness, fatigue, and sleep disruption are common following a mild traumatic brain injury. These findings further substantiate blue light therapy as a promising nonpharmacological approach to improve these sleep-related complaints with the added benefit of improved postconcussion symptoms and depression severity.

The Effect of Blue-enriched White Light on Cognitive Performances and Sleepiness of Simulated Shift Workers: A Randomized Controlled Trial

BACKGROUND

Shift work is associated with reduced performance and efficiency, the current study aimed at investigating whether blue-enriched white light could improve workers' performance.

METHODS

The study, which adopted a randomized controlled trial, was conducted among 48 simulated shift workers. The participants performed sustained attention task, working memory task, and sleepiness task during night shift work. The data was analyzed using two-way repeated measure ANOVA.

RESULTS

The results indicated that, compared to conventional light, participants' correct responses of the sustained attention significantly increased when they were exposed to blue-enriched white light, correspondingly, the commission errors and omission errors declined. Furthermore, the blue-enriched white light had a significant effect on the decrease of sleepiness. However, the working memory was not significantly affected.

CONCLUSION

Exposing to blue-enriched white light can improve sustained attention and reduce sleepiness.