面向入睡准备阶段的照明设计

ABSTRACT Light is the main environmental signal synchronizing circadian rhythms to the 24-hour light-dark cycle. Recent research has identified significant inter-individual variability in the sensitivity of the circadian system to light as measured by, among other indicators, melatonin suppression in response to light. These inter-individual differences in light sensitivity could result in differential vulnerability to circadian disruption and related impacts on health. A growing body of experimental evidence points to specific factors which are associated with variability in the melatonin suppression response; however, no review to date has summarized this research to present a comprehensive summary of current knowledge. The aim of this review is to provide an overview of the state of this evidence, which to date spans demographic, environmental, health-related, and genetic characteristics. Overall, we find that there is evidence of inter-individual differences for the majority of the characteristics examined, although research on many factors remains limited. Knowledge of individual factors that are linked to light sensitivity could inform improved lighting personalization, as well as the use of measures of light sensitivity to determine disease phenotypes and treatment recommendations.

We compared the effects of bedroom-intensity light from a standard fluorescent and a blue- (ie, short-wavelength) depleted LED source on melatonin suppression, alertness, and sleep. …

ABSTRACT Light is necessary for life, and artificial light improves visual performance and safety, but there is an increasing concern of the potential health and environmental impacts of light. Findings from a number of studies suggest that mistimed light exposure disrupts the circadian rhythm in humans, potentially causing further health impacts. However, a variety of methods has been applied in individual experimental studies of light-induced circadian impacts, including definition of light exposure and outcomes. Thus, a systematic review is needed to synthesize the results. In addition, a review of the scientific evidence on the impacts of light on circadian rhythm is needed for developing an evaluation method of light pollution, i.e., the negative impacts of artificial light, in life cycle assessment (LCA). The current LCA practice does not have a method to evaluate the light pollution, neither in terms of human health nor the ecological impacts. The systematic literature survey was conducted by searching for two concepts: light and circadian rhythm. The circadian rhythm was searched with additional terms of melatonin and rapid-eye-movement (REM) sleep. The literature search resulted to 128 articles which were subjected to a data collection and analysis. Melatonin secretion was studied in 122 articles and REM sleep in 13 articles. The reports on melatonin secretion were divided into studies with specific light exposure (101 reports), usually in a controlled laboratory environment, and studies of prevailing light conditions typical at home or work environments (21 studies). Studies were generally conducted on adults in their twenties or thirties, but only very few studies experimented on children and elderly adults. Surprisingly many studies were conducted with a small sample size: 39 out of 128 studies were conducted with 10 or less subjects. The quality criteria of studies for more profound synthesis were a minimum sample size of 20 subjects and providing details of the light exposure (spectrum or wavelength; illuminance, irradiance or photon density). This resulted to 13 qualified studies on melatonin and 2 studies on REM sleep. Further analysis of these 15 reports indicated that a two-hour exposure to blue light (460 nm) in the evening suppresses melatonin, the maximum melatonin-suppressing effect being achieved at the shortest wavelengths (424 nm, violet). The melatonin concentration recovered rather rapidly, within 15 min from cessation of the exposure, suggesting a short-term or simultaneous impact of light exposure on the melatonin secretion. Melatonin secretion and suppression were reduced with age, but the light-induced circadian phase advance was not impaired with age. Light exposure in the evening, at night and in the morning affected the circadian phase of melatonin levels. In addition, even the longest wavelengths (631 nm, red) and intermittent light exposures induced circadian resetting responses, and exposure to low light levels (5–10 lux) at night when sleeping with eyes closed induced a circadian response. The review enables further development of an evaluation method of light pollution in LCA regarding the light-induced impacts on human circadian system.

Light elicits a range of non‐visual responses in humans. Driven predominantly by intrinsically photosensitive retinal ganglion cells (ipRGCs), but also by rods and/or cones, these responses include melatonin suppression. A sigmoidal relationship has been established between melatonin suppression and light intensity; however, photoreceptoral involvement remains unclear.

… This study investigated how light exposure duration affects melatonin suppression, a well-established marker of circadian phase, and whether adolescents (13–18 years) are more …

Significance Using data from 100 healthy young participants studied during a 9-d inpatient protocol, we constructed analytic action spectra for melatonin suppression and circadian phase resetting in response to 6.5-h monochromatic light exposures and fit these action spectra with linear combinations of melanopsin (ipRGC), short-wavelength (S), and combined long and medium-wavelength (L+M) cone functions. First, we demonstrate that melatonin suppression is driven approximately equally by S and L+M cones in the first quarter of light exposure and melanopsin only over longer durations. Second, we demonstrate that S cones may contribute significantly to the overall phase resetting given the nonlinear relationship between light duration and magnitude of resetting. These findings indicate that the spectral sensitivity of circadian light responses changes over time.

… of different lighting conditions on melatonin suppression and … of 19 different polychromatic lighting conditions, for 30 minutes … Therefore, we cannot exclude any circadian phase delaying …

… light level for melatonin suppression such that lighting in homes would not stimulate the circadian … Rea and Figueiro used a CS value of 0.05 (equivalent to 5% melatonin suppression) …

Wavelength comparisons have indicated that circadian phase-shifting and enhancement of subjective and EEG-correlates of alertness have a higher sensitivity to short wavelength visible light. The aim of the current study was to test whether polychromatic light enriched in the blue portion of the spectrum (17,000 K) has increased efficacy for melatonin suppression, circadian phase-shifting, and alertness as compared to an equal photon density exposure to a standard white polychromatic light (4000 K). Twenty healthy participants were studied in a time-free environment for 7 days. The protocol included two baseline days followed by a 26-h constant routine (CR1) to assess initial circadian phase. Following CR1, participants were exposed to a full-field fluorescent light (1 × 1014 photons/cm2/s, 4000 K or 17,000 K, n = 10/condition) for 6.5 h during the biological night. Following an 8 h recovery sleep, a second 30-h CR was performed. Melatonin suppression was assessed from the difference during the light exposure and the corresponding clock time 24 h earlier during CR1. Phase-shifts were calculated from the clock time difference in dim light melatonin onset time (DLMO) between CR1 and CR2. Blue-enriched light caused significantly greater suppression of melatonin than standard light ((mean ± SD) 70.9 ± 19.6% and 42.8 ± 29.1%, respectively, p < 0.05). There was no significant difference in the magnitude of phase delay shifts. Blue-enriched light significantly improved subjective alertness (p < 0.05) but no differences were found for objective alertness. These data contribute to the optimization of the short wavelength-enriched spectra and intensities needed for circadian, neuroendocrine and neurobehavioral regulation.

The human circadian system is primarily regulated by the 24-h LD cycle incident on the retina, and nocturnal melatonin suppression is a primary outcome measure for characterizing the biological clock’s response to those light exposures. A limited amount of data related to the combined effects of light level, spectrum, and exposure duration on nocturnal melatonin suppression has impeded the development of circadian-effective lighting recommendations and light-treatment methods. The study’s primary goal was to measure nocturnal melatonin suppression for a wide range of light levels (40 to 1000 lux), 2 white light spectra (2700 K and 6500 K), and an extended range of nighttime light exposure durations (0.5 to 3.0 h). The study’s second purpose was to examine whether differences existed between adolescents’ and adults’ circadian sensitivity to these lighting characteristics. The third purpose was to provide an estimate of the absolute threshold for the impact of light on acute melatonin suppression. Eighteen adolescents (age range, 13 to 18 years) and 23 adults (age range, 24 to 55 years) participated in the study. Results showed significant main effects of light level, spectrum, and exposure duration on melatonin suppression. Moreover, the data also showed that the relative suppressing effect of light on melatonin diminishes with increasing exposure duration for both age groups and both spectra. The present results do not corroborate our hypothesis that adolescents exhibit greater circadian sensitivity to short-wavelength radiation compared with adults. As for threshold, it takes longer to observe significant melatonin suppression at lower CS levels than at higher CS levels. Dose-response curves (amount and duration) for both white-light spectra and both age groups can guide lighting recommendations when considering circadian-effective light in applications such as offices, schools, residences, and healthcare facilities.

… The 24-hour light–dark cycle and its light exposure regulate our circadian rhythms and affect our mood, daytime functioning and nighttime sleep. These effects are strongly mediated by …

A better understanding of the spatial sensitivity of the human circadian system to photic stimulation can provide practical solutions for optimized circadian light exposures. Two psychophysical experiments, involving 25 adult participants in Experiment 1 (mean age = 34.0 years [SD 15.5]; 13 females) and 15 adult participants in Experiment 2 (mean age = 43.0 years [SD 12.6]; 12 females), were designed to investigate whether varying only the spatial distribution of luminous stimuli in the environment while maintaining a constant spectrally weighted irradiance at the eye could influence nocturnal melatonin suppression. Two spatial distributions were employed, one where the luminous stimulus was presented On-axis (along the line of sight) and one where two luminous stimuli were both presented Off-axis (laterally displaced at center by 14°). Two narrowband LED light sources, blue (λmax = 451 nm) for first experiment and green (λmax = 522 nm) for second experiment, were used in both the On-axis and the Off-axis spatial distributions. The blue luminous stimulus targeting the fovea and parafovea (On-axis) was about three times more effective for suppressing melatonin than the photometrically and spectrally matched stimulus targeting the more peripheral retina (Off-axis). The green luminous stimulus targeting the fovea and parafovea (On-axis) was about two times more effective for suppressing melatonin than the photometrically and spectrally matched stimulus targeting the more peripheral retina (Off-axis).

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

A physiologically based model of arousal dynamics is improved to incorporate the effects of the light spectrum on circadian phase resetting, melatonin suppression, and subjective sleepiness. To account for these nonvisual effects of light, melanopic irradiance replaces photopic illuminance that was used previously in the model. The dynamic circadian oscillator is revised according to the melanopic irradiance definition and tested against experimental circadian phase resetting dose‐response and phase response data. Melatonin suppression function is recalibrated against melatonin dose‐response data for monochromatic and polychromatic light sources. A new light‐dependent term is introduced into the homeostatic weight component of subjective sleepiness to represent the direct alerting effect of light; the new term responds to light change in a time‐dependent manner and is calibrated against experimental data. The model predictions are compared to a total of 14 experimental studies containing 26 data sets for 14 different spectral light profiles. The revised melanopic model shows on average 1.4 times lower prediction error for circadian phase resetting compared to the photopic‐based model, 3.2 times lower error for melatonin suppression, and 2.1 times lower error for subjective sleepiness. Overall, incorporating melanopic irradiance allowed simulation of wavelength‐dependent responses to light and could explain the majority of the observations. Moving forward, models of circadian phase resetting and the direct effects of light on alertness and sleep need to use nonvisual photoreception‐based measures of light, for example, melanopic irradiance, instead of the traditionally used illuminance based on the visual system.

The influence of light exposure on human circadian rhythms has been widely recognized. This effect is mediated by a phototransduction process projected by the intrinsically photosensitive retinal ganglion cells (ipRGCs). The process also involves signal inputs from visual photoreceptors. However, the relative contributions of each photoreceptor to this process remain unclear; accordingly, two different types of circadian lighting models have been proposed: (i) the melanopic illuminance model based solely on ipRGC activation, including melanopic equivalent daylight D65 illuminance (m-EDI) and equivalent melanopic illuminance (EML), and (ii) the circadian stimulus (CS) model, which considers the participation of both ipRGC and visual photoreceptors. However, the two models can yield conflicting predictions. In this study, we assessed and compared the accuracies of these circadian lighting models by fitting a substantial amount of experimental data extracted from multiple laboratory studies. Upon evaluating the results across all exposure durations, data-fitting accuracy of the intricate CS model did not surpass that of the much simpler melanopic illuminance model. Consequently, the latter appears to be the more suitable model for lighting applications. Moreover, a recurring limitation of prior research was revealed: the lighting spectra were not tailored to effectively reflect the fundamental distinctions between the two types of models. Therefore, drawing clear conclusions regarding the accuracies of the models is challenging. To address this problem, we introduced a method for designing contrast-spectra pairs. This method can provide lighting spectra to highlight the difference in circadian illuminance based on one model while keeping the circadian illuminance of others constant.

This study investigates the effects of melanopic illuminance on pupil diameter under constant indirect corneal illuminance. A total of 45 participants were recruited and exposed to four lighting conditions: a dim light control (12.3 lx, m-EDI = 1.9 lx) and three experimental conditions with the same corneal illuminance (75 lx) but different m-EDI levels (13.1 lx, 22.1 lx, and 33.3 lx). The experiment was conducted at night, starting at 7:30 PM and ending at 9:30 PM. Participants were exposed to dim light for 1 hour, and then randomly assigned to one of the four lighting conditions for another 1 hour. Pupil diameter was recorded at the end of each phase. Results showed that even under constant indirect corneal illuminance, variations in m-EDI could significantly modulate steady-state pupil responses.

Natural and artificial lighting have the ability to produce visual and non-visual effects on human beings. There are four well-known photoreceptors: cones on one hand, and L, M, and S type rods on the other, which are associated with the visual system and allow for a differentiation of color and tone of objects based on reflected light. On the other hand, non-visual effects depend on another recently discovered photoreceptor known as Intrinsically Photosensitive Retinal Ganglion Cells (ipRGC), which when excited primarily suppress melatonin, a hormone that regulates Circadian Rhythms (CR), and can also affect biological and psychological processes. This work presents a study on integrative lighting, focused on the analysis of methods and parameters for calculating factors used in lighting design, such as Circadian Stimulus (CS), Equivalent Melanopic Lux (EML), etc., and their combination with traditional lighting design parameters such as Color Rendering Index (CRI), Correlated Color Temperature (CCT), chromatic coordinates, TM-30 color standard, among others. Furthermore, emphasis is placed on the use of the CIE-S-026:2018 standard, which establishes sensitivity curves associated with photoreceptors of the human visual system. It is determined that the Melanopic Illuminance parameter (m-EDI) is currently the determining factor for evaluating non-visual effects. Thus, a parameterization methodology is proposed in order to design a Human-Centered Integrative Lighting System (HCILS).

… cells (ipRGCs) play a … illuminance and the accuracy of the m-EDI and EML metrics, we designed a pair of general-lighting spectra with equivalent melanopic and photopic illuminance …

In the context of intelligent and integrative lighting, in addition to the need for color quality and brightness, the non-visual effect is essential. This refers to the retinal ganglion cells (ipRGCs) and their function, first proposed in 1927. The melanopsin action spectrum has been published in CIE S 026/E: 2018 with the corresponding melanopic equivalent daylight (D65) illuminance (mEDI), melanopic daylight (D65) efficacy ratio (mDER) and 4 other parameters. Due to the importance of mEDI and mDER, this work synthesizes a simple computational model of mDER as the main research objective, based on a database of 4214 practical spectral power distributions (SPDs) of daylight, conventional, LED, and mixed light sources. In addition to the high correlation coefficient R2 of 0.96795 and the 97% confidence offset of 0.0067802, the feasibility of the mDER model in intelligent and integrated lighting applications has been extensively tested and validated. The uncertainty between the mEDI calculated directly from the spectra and that obtained by processing the RGB sensor and applying the mDER model has reached ± 3.3% after an appropriate matrixing process and proper illumination characterization combined with the successful mDER calculation model. This result opens the potential of low-cost RGB sensors for applications in intelligent and integrative lighting systems to optimize and compensate the non-visual effective parameter mEDI using daylight and artificial light in indoor spaces. The goal of the research on RGB sensors and the corresponding processing method are also presented and their feasibility is methodically demonstrated. A comprehensive investigation with a huge amount of color sensor sensitivities is necessary in a future work of other researches.

ABSTRACT Intrinsic circadian clocks control the sleep patterns of most species on the earth. Having a natural period ~10’ longer than 24 h, they must be reset to the natural day/night cycle daily. The critical input (Zeitgeber) “resetting” this internal clock is the temporal variation of the spectrum and intensity of light across the 24-h day. To develop artificial lighting that mirrors sunlight in an individually tailored, dynamic way to control melatonin suppression correctly and provide adequate vision on a 24-h circadian cycle, open-source code is needed to adjust and optimize the weighting of the various LEDs chosen for the system. Spectral differences between batches of LEDs and differences in room layout require code to fine tune the weightings of the LEDs. Making use of existing spreadsheets (CIE α-opic, CIE1931, CCT, Duv Tolerance (Duv (T)) (CIE 2017)) and the data concerning the LEDs spectral power distribution (SPD), power consumption, cost and spectra, open-source C-code was written to build spectra, calculate a spectrum’s visual and nonvisual optical parameters along with power consumption (a key practical concern). An evaluation function, suitable for use in either brute-force or AI-assisted optimization, was written. As an example, this was used to optimize parameters to aid in establishing tailored 24-h dynamic white lighting systems. Hardware was developed to implement the optimized spectra, and the lighting system was deployed in a long-term care environment.

Recent studies have highlighted the key role of lighting in regulating circadian rhythms and its impact on human health. Exposure to blue light, especially at specific times of day, is now quantified using the melanopic Equivalent Daylight Illuminance (m-EDI) parameter, defined in the CIE S 026 standard. This parameter is proportional to the integral, in the visible range, of the spectral power distribution and the melanopic sensitivity function, which peaks near 490 nm, and is similar to a Gaussian distribution. Low-cost spectrometric sensors using photodiode arrays and narrowband filters offer a cost-effective way to estimate m-EDI through a weighted sum of channel responses. However, due to inherent sensor variability, individual calibration is recommended. The standard approach involves multiple linear regression to fit the sensor’s output to reference values using a set of test light sources. This method is easy to implement but depends heavily on the selection of calibration illuminants, which must outnumber the channels. This paper analyzes the sensitivity of this method to the sensor’s spectral response and the choice of calibration sources. A revised calibration approach is proposed, selectively discarding channels to reduce deviations from the target response. Applied to several sensors, this method significantly improves calibration accuracy and robustness, reducing the RMS error for several test LEDs from 17.6 to 1.36 lux.

… However, the effects of different dynamic transition patterns, particularly variations in melanopic equivalent daylight illuminance (m-EDI) intensity and duration, on non-visual and visual …

Abstract Study Objectives Blue-depleted lighting reduces the disruptive effects of evening artificial light on the circadian system in laboratory experiments, but this has not yet been shown in naturalistic settings. The aim of the current study was to test the effects of residing in an evening blue-depleted light environment on melatonin levels, sleep, neurocognitive arousal, sleepiness, and potential side effects. Methods The study was undertaken in a new psychiatric hospital unit where dynamic light sources were installed. All light sources in all rooms were blue-depleted in one half of the unit between 06:30 pm and 07:00 am (melanopic lux range: 7–21, melanopic equivalent daylight illuminance [M-EDI] range: 6–19, photopic lux range: 55–124), whereas the other had standard lighting (melanopic lux range: 30–70, M-EDI range: 27–63, photopic lux range: 64–136), but was otherwise identical. A total of 12 healthy adults resided for 5 days in each light environment (LE) in a randomized cross-over trial. Results Melatonin levels were less suppressed in the blue-depleted LE (15%) compared with the normal LE (45%; p = 0.011). Dim light melatonin onset was phase-advanced more (1:20 h) after residing in the blue-depleted LE than after the normal LE (0:46 h; p = 0.008). Total sleep time was 8.1 min longer (p = 0.032), rapid eye movement sleep 13.9 min longer (p < 0.001), and neurocognitive arousal was lower (p = 0.042) in the blue-depleted LE. There were no significant differences in subjective sleepiness (p = 0.16) or side effects (p = 0.09). Conclusions It is possible to create an evening LE that has an impact on the circadian system and sleep without serious side effects. This demonstrates the feasibility and potential benefits of designing buildings or hospital units according to chronobiological principles and provide a basis for studies in both nonclinical and clinical populations.

Background: Insomnia is increasingly recognized for its marked impact on public health and is often associated with various adverse health outcomes, including cardiovascular diseases and mental health disorders. The aim of this study was to investigate the efficacy of pre-sleep dim light therapy (LT) as a non-pharmacological intervention for insomnia in adults, assessing its influence on sleep parameters and circadian rhythms. Methods: A randomized, open-label, two-arm clinical trial was conducted over two weeks with 40 participants aged 20–60 years, all of whom had sleep disorders (CRIS, KCT0008501). They were allocated into control and LT groups. The LT group received exposure to warm-colored light, minimizing the blue spectrum, before bedtime. The study combined subjective evaluation via validated, sleep-related questionnaires, objective sleep assessments via actigraphy, and molecular analyses of circadian clock gene expression in peripheral blood mononuclear cells. Baseline characteristics between the two groups were compared using an independent t-test for continuous variables and the chi-squared test for categorical variables. Within-group differences were assessed using the paired t-test. Changes between groups were analyzed using linear regression, adjusting for each baseline value and body mass index. The patterns of changes in sleep parameters were calculated using a linear mixed model. Results: The LT group exhibited significant improvements in sleep quality (difference in difference [95% CI]; −2.00 [−3.58, −0.43], and sleep efficiency (LT: 84.98 vs. control: 82.11, p = 0.032), and an advanced Dim Light Melatonin Onset compared to the control group (approximately 30 min). Molecular analysis indicated a significant reduction in CRY1 gene expression after LT, suggesting an influence on circadian signals for sleep regulation. Conclusions: This study provides evidence for the efficacy of LT in improving sleep quality and circadian rhythm alignment in adults with insomnia. Despite limitations, such as a small sample size and short study duration, the results underscore the potential of LT as a viable non-pharmacological approach for insomnia. Future research should expand on these results with larger and more diverse cohorts followed over a longer period to validate and further elucidate the value of LT in sleep medicine. Trial registration: The trial was registered with the Clinical Research Information Service (KCT0008501).

Abstract The sleep-wake and circadian cycles are influenced by light, particularly in the short-wavelength portion of the visible spectrum. Most personal light-emitting electronic devices are enriched in this so-called “blue” light. Exposure to these devices in the evening can disturb sleep. Interventions to reduce short-wavelength light exposure before bedtime may reduce adverse effects on sleep. We conducted a systematic review and meta-analysis to examine the effect of wearing color-tinted lenses (e.g. orange or amber) in frames to filter short-wavelength light exposure to the eye before nocturnal sleep. Outcomes were self-reported or objective measures of nocturnal sleep. Relatively few (k = 12) studies have been done. Study findings were inconsistent, with some showing benefit and others showing no effect of intervention. Meta-analyses yielded a small-to-medium magnitude combined effect size for sleep efficiency (Hedge’s g = 0.31; 95% CI: −0.05, 0.66; I2 = 38.16%; k = 7), and a small-to-medium combined effect size for total sleep time (Hedge’s g = 0.32; 95% CI: 0.01, 0.63; I2 = 12.07%; k = 6). For self-report measures, meta-analysis yielded a large magnitude combined effects size for Pittsburgh Sleep Quality Index ratings (Hedge’s g = −1.25; 95% CI: −2.39, −0.11; I2 = 36.35%; k = 3) and a medium combined effect size for total sleep time (Hedge’s g = 0.51; 95% CI: 0.18, 0.84; I2 = 0%; k = 3), Overall, there is some, albeit mixed, evidence that this approach can improve sleep, particularly in individuals with insomnia, bipolar disorder, delayed sleep phase syndrome, or attention-deficit hyperactive disorder. Considering the ubiquitousness of short-wavelength-enriched light sources, future controlled studies to examine the efficacy of this approach to improve sleep are warranted. Systematic review registration: PROSPERO 2018 CRD42018105854.

ABSTRACT Objectives This study examined the effects of bedroom lighting with pre-bedtime activities two hours before bedtime on sleepiness and polysomnography (PSG) sleep in community-dwelling adults with poor sleep. Methods A balanced crossover design was used with 24 healthy adults. Four lighting conditions under two activity situations (unrestricted (A1) and restricted (A2) electronic device use two hours before bedtime) were tested using adjustable LED lights: (E2: 3000K, 160 lux; E3: 5000K → 3000K, 160 → 30 lux; E4: 5000K, 160 lux) and compared to standard fluorescent lighting (E1: 5000K, 160 lux). The protocol lasted 8 nights (4 lightings × 2 activity conditions), with the whole night PSGmeasure, subjective sleep perception at wake-up, and sleepiness (Stanford Sleepiness Scale) measured hourly 2 hr before bedtime. Results Results showed that sleep latency was 10.62 min longer when exposed to 5000k LED light than to 5000k FL. Exposure to other lower color temperature lights did not have a significant difference in sleepiness and PSGsleep. However, participants felt drowsier and had a shorter PSG sleep latency of 6.08 min when the use of electronic devices was not allowed. Conclusion A 5000k LED light leads to longer sleep latency compared to a 5000k fluorescent light. Restriction of electronic device use before bedtime improves sleep onset in healthy adults. Managing ambient light exposure with lower color temperature LED light and reducing electronic device use 2 hr before bedtime may improve sleep quality in healthy adults.

… lighting pre-sleep environment can reduce sleep latency, wakefulness, and light sleep, and … , and the appropriate CCT should consider the impact of blue light. This research provides a …

… and applied research on the non-visual effects of light in the last more than 20 years, but lighting … We investigated the effects of three-hour pre-sleep lighting intervention on melatonin, …

This study assesses the effectiveness of pre-sleep dim light therapy (LT) as a non-pharmacological intervention for insomnia in adults, focusing on its impact on sleep quality and circadian rhythms. Conducted over two weeks, the randomized trial involved 40 adults with sleep disorders. Participants were divided into a control group and an LT group, the latter receiving warm-colored light exposure before bedtime. The methodology combined subjective sleep questionnaires, objective sleep assessments through actigraphy, and molecular analyses of circadian clock gene expression in blood cells. Key results indicated significant improvements in the LT group’s sleep quality and efficiency, and a 30-minute advancement in Dim Light Melatonin Onset compared to the control group. Molecular analysis revealed a notable reduction in CRY1 gene expression, implicating LT’s influence on circadian sleep regulation. While the study’s small sample size and short duration limit its scope, the findings suggest LT’s potential as an effective, non-drug approach for insomnia treatment. The study advocates for expanded research with larger, more diverse cohorts over longer periods to further validate LT’s efficacy in sleep medicine.

… pre-sleep use of light-emitting devices to higher rates of insomnia in various countries. Amber lenses that block blue light … the importance of reducing blue light exposure for NICU nurses…

Increased blue-enriched morning light is often said to support circadian rhythm synchronization. Through a better sleep quality, one's cognitive and emotional functioning can also be enhanced. However, it is unclear which light characteristics (especially illuminance at eye level) are necessary to obtain a wellbeing effect in employees. This field study investigated different lighting conditions in a truck factory. 71 shift workers participated in the study during their morning shift (6 am - 2 pm). Measurements of sleep (MotionWatch8), attention (D2 attention task, go no-go computer task) and visual comfort (questionnaire) were administered before and after changing the lighting conditions. A Human Centric Lighting-condition (HCL; vertical melanopic equivalent daylight illuminance (MEDI) = 250 lux, CCT=5000 K; N = 33) was compared with a control LED-condition (MEDI = 44 lux, CCT=4000K; N = 38). Results show that workers in the HCL-condition showed a larger improvement in sleep efficiency (p=.057) and concentration (p=.01) than the control LED-group. No differences were found in visual comfort between groups. Preliminary results are promising and show that 250 MEDI might be a sufficient cut-off to stimulate workers' sleep and cognition. The high illuminance level was not detrimental in the HCL condition for the perceived visual comfort. Blue-enriched morning light supports sleep and concentration in shift workers. High illuminance levels are not detrimental for the perceived visual comfort.

The global phenomenon of population aging presents a significant challenge, affecting both the increasing number of older individuals and their duration of living with disability. Tailored care services are crucial for improving the quality of life of older adults, particularly those with disabilities residing in nursing homes. However, ensuring personalized care and mitigating the risks associated with institutionalization are essential in optimizing care quality. One particular challenge in nursing homes is maintaining residents' personal routines and addressing sleep disturbances linked to neurodegenerative disorders. Non-pharmacological interventions are increasingly recognized as preventive and management strategies for behavioral and psychiatric symptoms in nursing home residents. Sleep disruptions, such as reduced duration and increased nocturnal awakenings, are prevalent among nursing home residents. Excessive nocturnal lighting and frequent caregiver interventions contribute to these disturbances. This study aimed to investigate the impact of implementing smart humancentric lighting on the sleep efficiency of nursing home residents. Data from pressure sensors embedded in mattresses were collected to assess sleep efficiency. The findings suggest that smart humancentric lighting can significantly reduce sleep disturbances and improve sleep quality in nursing home residents. Future research should delve into specific symptoms, care burden, and psychotropic agent utilization to validate the effectiveness of this intervention.

Smart Buildings with connected lighting and sensors have become one of the first large-scale applications of the Internet of Things. However, existing efforts to make buildings smarter focus mainly on energy conservation and cutting costs. In this paper, we further address the beneficial effects of light upon humans. People nowadays spend more than 90% indoors and as such the indoor environment becomes paramount for people’s health and wellbeing. We present a Human Centric Lighting solution that supports human health through the estimation of the biological effects of light. It exploits the possibility that IoT offers to monitor humans and their experience and to control internet-connected lights. Despite the existence of well-established and extensively tested models of the circadian mechanism, benefits of those models are not yet harvested in practical applications. We envision an application that controls the lighting system based on a suitable model that predicts the human response to light. Our work confirms that the statistical signal processing approach of a Particle Filter can account for sensor and model uncertainties. We show how the response of the biological clock to light depends largely on individual characteristics, such as the intrinsic characteristic duration of the day, and therefore we include such person characterization into our system design.

… lighting design strategies. Although the dataset 34 used did not permit personalized lighting … the development of personalized light environment models and advance human-centric 745 …

Human centric lighting is an umbrella concept which covers human health and well-being in general. As the conventional lighting techniques are based on horizontal workplane illuminance, it drives from the vertical eye level illuminance and its spectral distribution triggering the non-visual effects on humans. That is named as melanopic illuminance consequently. Its metrics have taken their place in lighting design literature and applications, with emergence of related standards subsequently. This literature overview contributes about the understanding the meaning human centric lighting due to transition from visual to non-visual effects of light, and how they direct recent research through light's impacts on human performance, emotions health and well-being, and relations to energy saving even. The shift from the concept of human centric lighting to circadian lighting design is obvious in very current studies.

Beyond visual function, specialized light-sensitive retinal circuits involving the photopigment melanopsin drive critical aspects of human physiology and behavior, including sleep–wake rhythms, hormone production, mood, and cognition. Fundamental discoveries of visual neurobiology dating back to the 1990s have given rise to strong interest from the lighting industry in optimizing lighting to benefit health. Consequently, evidence-based recommendations, regulations, and policies need to translate current knowledge of neurobiology into practice. Here, reviewing recent advances in understanding of NIF circuits in humans leads to proposed strategies to optimize electric lighting. Highlighted knowledge gaps must be addressed urgently, as well as the challenge of developing personalized, adaptive NIF lighting interventions accounting for complex individual differences in physiology, behavior, and environment. Finally, lighting equity issues appear in the context of marginalized groups, who have traditionally been underserved in research on both fundamental visual processes and applied lighting. Biologically optimal light is a fundamental environmental right.

Background and purpose Maternal circadian rhythms are important for maintaining maternal and fetal homeostasis. The maternal circadian system coordinates the internal clock of the fetus with environmental lighting conditions via the melatonin signal. The intensity and wavelength of daylight influence nocturnal melatonin production. This study aims to evaluate the effect of environmental lighting conditions on melatonin production in pregnant women with reduced mobility during hospitalization. Methods We installed a human-centric lighting system with biodynamic effects (BDL, biodynamic lighting) in the patient rooms. The pregnant women in the patient rooms with standard indoor conditions served as a control group. The illuminance (lux) and dose of effective circadian irradiation (Hec) were recorded every 10 seconds by light dosimeters (Lucerne University, Switzerland) attached to the patients` clothing. Results We analyzed the illuminance status of 47 pregnant women with a median (IQR) gestational age of 29.9 (25.4-32.3) weeks of gestation. The median illuminance in the control group was significantly lower (p<0.05) than in the BDL group in the morning and afternoon from day 1 to 5. BDL patients had a significantly higher effective circadian irradiation in the morning. The effective circadian irradiation showed a significant daily rhythm only in the BDL group. The BDL group had a significantly higher melatonin production on day 3 (p=0.006) and day 5 (p=0.012) than the control group median (IQR) nocturnal 6-Sulfatoxymelatonin excretion 15840 (10140-22160) ng/12h vs. 6141 (2080-11328) ng/12h on day 3 and 18780 (11320-23562) ng/12h vs. 6380 (3500-17600) ng/12h on day 5). Conclusion We have demonstrated that dramatically altered lighting conditions of hospitalized pregnant women may be optimized by installing biodynamic lighting systems in the patient rooms resulting in the maintenance of nocturnal melatonin production in pregnant women.

ABSTRACT As many aspects of animal, human and plant behavior and survival are being perturbed by widespread exposure to artificial light at night (ALAN), lighting professionals are in the middle, attempting to make design decisions that directly affect these life forms. Research shows any light exposure higher than the nighttime natural environment will have a negative impact on various life forms during the nocturnal phase. This paper aims to provide a design process for “life-centric” lighting with good human and non-human outcomes for all life-sustaining behaviors on earth driven by phototropism, phototaxis, photoperiodism and circadian entrainment as the foundational consideration. Fundamental understandings of how light information is used by these life forms in a way crucial for development, growth and survival is provided in the paper. Key references are consolidated and synthesized using PRISMA 2020 with goals of supporting knowledge translation into pragmatic lighting strategies in a manner useful for lighting professionals. A process for life-centric lighting design using an existing process for human-centric lighting design involving lighting intensity and spectrum along with spatial and temporal patterns is provided, which can dovetail with decision-making processes that are within the workflow of lighting professionals. Well-designed studies with a wider range of light intensities and spectrum and well-defined lighting properties, along with better modes of communication between lighting professionals and ALAN researchers are recommended to facilitate the realization of biodynamic lighting solutions that will support good human and non-human outcomes.

Abstract Dementia can disturb the circadian rhythm more than in normal ageing people. And their biological clock is often not enough stimulated by light. Sleep disturbances form a high burden for informal caregivers and is the main reason for institutionalization. The effect of biodynamic lighting with varying intensity and colour resembling a daylight curve has hardly been objectively researched. In this study, we evaluate the exposure to biodynamic lighting on circadian functioning of 13 patients with dementia admitted to a psychiatric hospital. Three biodynamic lighting armatures designed for home use were placed in the common area for a period of three weeks and then removed for the same period. These periods were intermittent in an AB-phase design. Objective data of the sleeping pattern were collected using a bed sensor. During exposure the average frequency of night-time bed wandering significantly decreased from 11 to 5 times (P = 0.002). The average frequency of daytime napping significantly decreased from 16 to 7 times (P = 0.004). The average total night-time sleep significantly increased from 408 to 495 min (P = 0.007). The average total time out of bed at night significantly decreased from 180 to 104 min (P = 0.006). This pilot study found promising evidence (effect sizes >0.5) that biodynamic lighting, tailored to stimulate circadian entrainment, could be helpful in decreasing sleeping disturbances in patients with dementia. This biodynamic lighting setup could easily be used as a non-pharmacological intervention in a home situation.

Background Bright Light Therapy is effective in improving sleep and circadian rhythms. However, little is known regarding the effects of BioDynamic Lighting. The current study examined whether BioDynamic Lighting is effective for improving sleep and rest-activity rhythms in nursing home residents with dementia, and compared its effects with those of Bright Light Therapy and standard light. Methods Forty-two residents with dementia were included in this nonrandomized 12-month crossover trial. Residents were exposed to BioDynamic Lighting, Bright Light Therapy, and standard light (twice), each for 3-months. The sleep parameters were measured via wrist-actigraphy and bed sensors. Results Multilevel regression analyses revealed no significant changes in the 24-h rest-activity and sleep variables intradaily variability, interdaily stability, amplitude, sleep efficiency, sleep onset latency, number of awakenings, duration of nocturnal awakenings, total sleep duration or night-time bed exits after 3 months of BioDynamic Lighting or Bright Light Therapy exposure compared to baseline. After BioDynamic Lighting discontinuation, we observed a significant increase in the number of nocturnal awakenings (d=0.35, p=.01), and a decrease in sleep onset latency (d=-0.47, p=.003). No significant differences were observed in the effects of BioDynamic Lighting and Bright Light Therapy. Conclusions Neither 3-month BioDynamic Lighting nor Bright Light Therapy had significant effects on night-time sleep, 24-h rest-activity rhythm (actigraphy), or bed exits during the night (bed sensors). Elements that may have influenced our results include suboptimal sleep hygiene, such as long bed episodes, daytime napping and scheduled afternoon rest periods. Future studies in larger, adequately powered samples are needed to confirm these results. Trial Registration Dutch Trial Register (NTR7480, Registration Date: 1-10-2018). Supplementary Information The online version contains supplementary material available at 10.1186/s12877-026-07365-2.

Exposure to natural daylight has a positive impact on human health and wellbeing. The non-visual effects of daylight stimulate a response in the circadian system which oversees fundamental mechanisms within the human body, such as metabolism, hormone balance and sleep-wake cycles. For people with dementia, the working capacity and regularity of these processes becomes further compromised as their exposure to daylight is reduced, due largely to age-contributing factors such as increased eye sensitivity and reduced mobility. In light of this, artificial lighting has been revolutionised to enable tailored output based on the photobiological demands of humans. This is known as biodynamic lighting which encompasses varying light intensity and spectral composition. Within dementia cohorts, this design concept has not been well studied, making it difficult to optimally administer and quantify related benefits. Fortunately, by building on the recent progression in the fields of machine learning and the internet of things, the potential for simultaneous behaviour monitoring and actuation of lighting intervention technologies is possible, enabling production of a viable biodynamic lighting solution. To this end, the present study provides a review of related work in the field of biodynamic technology designed to improve wellbeing in dementia, and identifies areas where improvements may be made. Following this, a proposed solution for future study designs and technologies is suggested. The proposed solution exists in the prototype stage, with a route to deploying in care facilities in the near future.

… of circadian response to melatonin production, we do not … Biodynamic Lighting (a new term is recently used in lieu of … important considerations about what “biodynamic” really means and …

… in secretion of the hormone melatonin and cortisol. … lighting system with installed tunable white luminaires controlled to simulate natural conditions can be called biodynamic lighting. …

… to the concepts of circadian lighting or biodynamic illumination introduced in previous years. … Evaluating potential spectral impacts of various artificial lights on melatonin suppression, …

Integrative lighting considers light for both visual and non-visual impact and can therefore benefit human health and well-being. More specifically, it can benefit circadian-related well-being, an umbrella term which within dementia cohorts considers factors such as sleep, rest-activity, mood, agitation and activities of daily living. As people living with dementia experience disruptions to their circadian rhythms and spend large amounts of time indoors, the understanding of how integrative interior lighting could influence their body clock could help support their well-being. A review of 18 studies found that papers are difficult to compare due to unsystematic study designs and reporting of study characteristics, light characteristics and participant characteristics. The findings at most imply that indoor integrative lighting could be beneficial to these aspects of well-being. This review finds suggestion that for this cohort there may be a relationship between colour variation and mood and agitation, alongside a relationship between intensity variation and sleep, and that the influence on rest-activity may be more unpredictable. These findings are inferred and due to heterogeneous study designs they are inconclusive. The outcome of this review therefore recommends future studies that follow systematic checklists for study designs which seek to test these inferred hypotheses within this cohort.

Due to the proven effect of light on human circadian rhythms, nowadays researchers and developers of lighting systems (LS) concentrate on the non-visual parameters of light and methods of ensuring a safe comfortable light environment. This requires optimisation of spectral power distribution (SPD). In this view the most promising and functional are RGBW systems due to their ability to change dynamically SPD and, hence, light parameters. In this work we explore two RGBW (red-greenblue-white) systems with different white LEDs (warm white and neutral white) and the space of visual and non-visual parameters that they can ensure. Visual parameters are studied in terms of colour rendering index, colour fidelity index and visual corneal illuminance while non-visual parameters are studied in terms of circadian light, circadian stimulus and circadian action factor. These parameters are calculated for different contribution of the components in a correlated colour temperature (CCT) range of 2500 – 7000K. In addition, acceptable criterion of the colour fidelity index above 85 is used. It is shown that under this condition the circadian action factor in the range of 0.33-0.98 can be obtained by changing the CCT and (or) colour fidelity index. Also an achievable area of the circadian stimulus versus corneal illuminance space for RGBW systems is found. It enables to choose optimal combination of CCT, circadian stimulus and corneal illuminance to provide the desired level of circadian effect with sufficient visual comfort depending on the daytime and field of system's implementation. This data is useful for LS manufacturers and lighting designers to create a comfortable lighting environment. Keywords - RGBW colour mixing, tunable white light, circadian effect, colour rendering, colour fidelity index.

… light's circadian stimulus based on the characteristics of light incident on human eyes. With the light… design, it is now possible to tune lighting's circadian and visual effects to suit the uses …

Optimization of solid-state lighting spectra is performed to achieve beneficial and tunable circadian effects. First, the minimum spectral circadian action factor (CAF) of 2700 K white light-emitting diodes (LEDs) is studied for applications where biologically active illumination is undesirable. It is found that white-LEDs based on (i) RGB chips, (ii) blue & red chips plus green phosphor, and (iii) blue chip plus green & red phosphors are the corresponding minimum-CAF solutions at color-rendering index (CRI) requirements of 80, 90, and 95, respectively. Second, maximum CAF tunability of LED clusters is studied for dynamic daylighting applications. A dichromatic phosphor-converted blue-centered LED, a dichromatic phosphor-converted green-centered LED, and a monochromatic red LED are grouped to obtain white spectra between 2700 K and 6500 K. A maximum CAF tunability of 3.25 times is achieved with CRI above 90 and luminous efficacy of radiation of 313 - 373 lm/W. We show that our approaches have advantages over previously reported solutions on system simplicity, minimum achievable CAF value, CAF tunability range, and light source efficacy.

… Circadian lighting means lighting that coincides with our … temperatures ranging from 4000 K to about 10,000 K. This period … , ranging from below 2700 K to 3500 K, represent the daylight …

Innovations in LED lighting technology have led to tremendous adoption rates and vastly improved the metrics by which they are traditionally evaluated–including color quality, longevity, and energy efficiency to name a few. Additionally, scientific insight has broadened with respect to the biological impact of light, specifically our circadian rhythm. Indoor electric lighting, despite its many attributes, fails to specifically address the biological responses to light. Traditional electric lighting environments are biologically too dim during the day, too bright at night, and with many people spending much of their lives in these environments, it can lead to circadian dysfunction. The lighting industry’s biological solution has been to create bluer days and yellower nights, but the technology created to do so caters primarily to the cones. A better call to action is to provide biologically brighter days and biologically darker nights within the built environment. However, current lighting design practices have specified the comfort and utility of electric light. Brighter intensity during the day can often be uncomfortable or glary, and reduced light intensity at night may compromise visual comfort and safety, both of which will affect user compliance. No single lighting solution will effectively create biologically brighter days and biologically darker nights, but rather a variety of parameters need to be considered. This paper discusses the contributions of spectral power distribution, hue or color temperature, spatial distribution, as well as architectural geometry and surface reflectivity, to achieve biologically relevant lighting.

… Therefore, light sources with correlated colour temperature from 2700 to 3000 K, colour rendering index superior to 80 and luminous flux around 400 lm were chosen for comparison. …

Humans can undergo circadian disruption and misalignment when living in closed environments without sufficient daylight. Therefore, it is of great significance to investigate the effects of artificial light on the circadian rhythm. In this work, the red, green, blue, warm white, and cool white (RGBWW) five-channel light-emitting diodes (LEDs) were fabricated as the only light sources in the closed environment. The LED mixed lighting showed a high color rendering index (CRI) all the time. During the day, the light simulated the daylight and increased the tunability of the circadian action factor (CAF) and correlated color temperature (CCT). At night, it maintained low CAF and CCT. Three subjects did irregular shift work in the closed environment for 38 days. Their plasma melatonin and daily activity were measured to assess the circadian rhythm. After 38 days, the subjects' peak melatonin times did not shift significantly (p = 0.676), while their peak melatonin concentrations increased apparently (p = 0.005). The start times of the least active 5-h period (L5) in one day fluctuated in a small range. The standard deviation (SD) was <15.11 min in most times. These results demonstrated that the subjects' rhythms maintained stable and were enhanced. The periods of circular cross-correlation between activity and CAF oscillated around 24 h (SD = 15.4 min), indicating the entrainment of light on the stable 24-h rhythm. It was concluded that the daylight-like LED lighting effectively entrained and enhanced the circadian rhythm in the closed environment.

… in sleep following evening wear of blue blocking glasses is mediated through the ipRGCs. The PIPR was utilised as an indirect measure of ipRGC activity to understand its contribution …

The circadian rhythms which govern the timing of our sleep– wake cycles synchronize most strongly with blue light. Because of this, blue light is enhanced in seasonal affective disorder therapeutic “happy” lights for morning use, and blue wavelengths are filtered from screens of many smart devices in the evening to reduce phase delays of sleep onset. It has been known for decades that visual photoreceptors are not required for the synchronization of circadian cycles to environmental light or “photoentrainment.” Both humans and mice which lack visual signals from dysfunctional or missing rods and cones continue to photoentrain and show other nonvisual light-driven phenomena, such as the pupillary light reflex (1, 2). As early as the 1920’s, Clyde Keeler identified a strain of mice with a mutation which rendered them visually blind but noted that their irises retained the ability to constrict when exposed to light (3, 4). It was not until 2002 that the responsible photoreceptor, named “melanopsin,” was identified in the mammalian retina outside of the visual rods and cones (5). Melanopsin responds most strongly to blue light (about 480 nm) and is expressed in a subset of retinal ganglion cells (RGCs) that send axons directly into the brain’s central circadian clock, the suprachiasmatic nucleus (6). These ganglion cells are called intrinsically photoreceptive RGCs (ipRGCs) (Fig. 1). In PNAS, St Hilaire et al. shed new light on the contribution of blue light-sensing cones into ipRGC pathways to regulate the circadian photoentrainment pathways in humans (7). The retina utilizes redundant photoreceptors that drive nonvisual light effects such as circadian entrainment, pupillary light reflexes, and acute melatonin suppression. Mice lacking any one class of photoreceptor—either mice without melanopsin or mice without rod/cone signaling—still photoentrain (8, 9). Only animals lacking a combination of outer-layer photoreceptors (rods/cones) and melanopsin lose the ability to synchronize their behavior to light. Mice which have only cones or only rods are also able to photoentrain, although the lighting conditions must be specifically tailored to the remaining photoreceptor (10, 11). However, all rod and cone signals sufficient for circadian photoentrainment pass exclusively through the ipRGCs (12). Thus, multiple photoreceptors feed nonvisual photic information to the brain in a serial pathway. The ipRGCs are peculiar compared to other RGCs in a number of ways. The dendrites of conventional RGCs make their terminal input connections with bipolar cells in discreet ON or OFF anatomical bands in the retina’s inner plexiform layer (IPL). As a general rule, the ganglion cells with synaptic connections closest to the ganglion cell layer respond when a light turns on (ON cells), and ganglion cells with dendritic arborizations terminating in the farther sublamina respond when a light turns off (OFF cells). While various classes of ipRGCs terminate in either or both of ON and OFF layers of the IPL, all intrinsic light responses are of the ON type—that is, action potentials are fired while a light is on (13). A further peculiarity of ipRGCs is their capacity for sustained firing of action potentials. While conventional ganglion cells quickly adapt and cease firing during prolonged light exposures, many ipRGCs will consistently produce action potentials under light exposures with durations as long as 10 h, and they continue to fire for minutes after the light has ceased (14, 15). Much work on ipRGCs has been carried out in mice without rods and cones, or in experiments in which the outer photoreceptors have been pharmacologically silenced. In both primate and mouse retinas, cones contribute to the electric responses of various types of ipRGC (16–18). The upstream circuitry by which cones communicate with ipRGCs is still being uncovered. Pathways have been identified in primate retinas which allow for short-wavelength sensitive cones (S-cones) to give excitatory input to one class of ipRGC and inhibitory to another (19, 20). So, while melanopsin is the most proximal photoreceptor to the brain and gives only an ON signal, its message is shaped by the outer photoreceptors. What does this mean functionally? What function do photoreceptors with overlapping spectral sensitivities uniquely contribute to a single circuit? One apparent difference between melanopsin and visual pigments is the rate of adaptation. In the pupillary light response, there are transient-fast responses mediated by visual photoreceptors and sustained-slow responses mediated by melanopsin activation (21, 22). It seems that a similar phenomenon is at play in the nonvisual light response of circadian photoentrainment. St Hilaire et al. now find similar transient vs. sustained functions of ipRGCs in human circadian phase shifting (7). Subjects were administered a 6.5-h light stimulation during a heroic 9-d temporal isolation. By establishing a baseline pattern of each of the 100 subjects’ melatonin rhythms, the authors were able to analyze changes throughout the light stimulation and during the following days. Circadian responses to various intensities of near-monochromatic light across the visible spectrum were

… morning is associated with better nocturnal sleep quality and whether higher light intensities … Participants reported sleep quality after each nocturnal sleep. Sleep quality was measured …

Exposure to light during overtime work at night in confined spaces may disrupt the normal circadian clock, affect hormone secretion, sleep quality and performance, thereby posing great risks to the physical and mental health of night workers. Integrative lighting should be adopted to reduce the disturbance of normal physiological rhythm, while meeting the visual requirements of work. Through adjustable LED (CCT 6000 K/2700 K) and different vertical illuminance, five lighting patterns with different circadian stimuli (CS = 0.60, 0.30. 0.20, 0.10 and 0.05) were conducted, respectively, in a sleep lab using a within-subject design. Each lighting pattern lasted for 5 h every night. Eight healthy adults were recruited to complete the night work and their salivary melatonin, Karolinska sleepiness scale (KSS), Psychomotor Vigilance Task (PVT) and sleep quality were tested. The results showed that subjective sleepiness and melatonin concentration increased rapidly under low intervention (CS = 0.05) with the best sleep quality, while they decreased in high intervention (CS = 0.60) at night and led to significantly higher levels of sleepiness the next morning (p < 0.05). For the PVT, the middle intervention (CS = 0.30) showed the lowest response time and least errors (p < 0.05), suggesting that appropriate illuminance can improve visual performance. To reduce biorhythm disruptions, lower lighting stimulation is preferred during night work. For difficult visual tasks, high illuminances may not improve visual performance; just a slight increase in the existing lighting levels is adequate. Lighting interventions have a clear impact on sleep improvement and work capacity for those working overtime, and they may be translatable to other shift work scenarios.

This study investigated the effects of two whole-day ambient lighting interventions applied in living rooms on the objective and subjective sleep quality in older adults. Both lighting …

… nocturnal light environment could boost performance on the cognitive tasks and promote sleep quality after … the effects of nocturnal light environments on the cognitive performances and …

Exposure to artificial light-at-night (ALAN) is increasing globally, and there are concerns around how ALAN may impact sleep, psychological and physical health. However, there is a lack of evidence in the literature on how individuals perceive ALAN relative to their sleeping environment and habits, and how such perceptions correspond to objectively assessed night-time illuminance at the level of the residence. This cross-sectional study examined how such perceptions associate with sleep quality, sleep timing, psychological distress and cognitive failures. Further we examined the association between illuminance levels calculated as the biologically-relevant melatonin-suppression index (MSI) and the self-report of perception of ALAN. Five hundred and fifty two adult participants completed a survey addressing perception of ALAN in sleep environment along with the Pittsburgh Sleep Quality Index, Munich Chronotype Questionnaire, Cognitive Failure Questionnaire and the General Health Questionnaire. We report that perception of external ALAN in the sleeping environment was associated with poorer sleep quality, more cognitive failures and greater psychological distress, when controlling for age, sex, house location and MSI. No associations were found between the perception of external ALAN and MSI scores, and MSI scores were not associated with scores on any of the self-report measures. Internal lighting passing into the sleeping environment was associated with poorer sleep quality but not with psychological wellbeing. Habitual use of light-emitting devices was associated with poorer psychological wellbeing but not with sleep quality and sleep timing. Perception of environmental noise annoyance at night was associated with higher psychological distress and poorer quality sleep, and the perception of noise annoyance was associated with perception of ALAN. These results may suggest heightened attentional bias towards ALAN associated with poor sleep quality and higher levels of psychological distress, and highlight the need for more granular approaches in the study of ALAN and sleep and psychological health in terms of levels individual ALAN exposure, and an interpretation that seeks to integrate biological and psychological perspectives.

People in closed spaces without daylight for a long time are prone to circadian rhythm desynchrony and sleep disorders. To explore the effects of different lighting patterns on circadian …

BACKGROUND Sleep disturbance in bipolar disorder (BD) is common and is associated with a risk for mood episode recurrence. Thus, it is important to identify factors that are related to sleep disturbance in BD. This cross-sectional study investigated the association between exposure to light at night (LAN) and sleep parameters in patients with BD. METHODS The sleep parameters of 175 outpatients with BD were recorded using actigraphy at their homes for seven consecutive nights and were evaluated using the Insomnia Severity Index (ISI). The average LAN intensity in the bedroom during bedtime and rising time was measured using a portable photometer, and the participants were divided into two groups: "Light" (≥5 lx) and "Dark" (<5 lx). The association between LAN and sleep parameters was tested with multivariable analysis by adjusting for potential confounder such as age, gender, current smoker, mood state, day length, daytime light exposure, and sedative medications. RESULTS After adjusting for potential confounder, the actigraphy sleep parameters showed significantly lower sleep efficiency (mean, 80.1%vs. 83.4%; p = 0.01), longer log-transformed sleep onset latency (2.9 vs. 2.6 min; p = 0.01), and greater wake after sleep onset (51.4 vs. 41.6 min; p = 0.02) in the Light group than in the Dark group. Whereas, there were no significant differences in the ISI scores between the groups. LIMITATIONS This was a cross-sectional study; therefore, the results do not necessarily imply that LAN causes sleep disturbance. CONCLUSIONS Reducing LAN exposure may contribute to improved sleep quality in patients with BD.

Evening exposure to electric light can acutely suppress melatonin levels and adversely affect subsequent sleep. We conducted a systematic review with meta-analysis investigating the influence of evening illuminance levels on polysomnographically (PSG)-assessed sleep. We also explored how melanopsin (expressed in melanopic equivalent daylight illuminance (EDI) affects human sleep features. We included polysomnographic laboratory sleep studies with healthy humans for effects of illuminance and exposure duration, for pre-sleep exposures between 6:00 p.m. to 1:00 a.m. From 440 identified articles, 114 met eligibility criteria for screening, and 21 also reported type of light source/spectral characteristics, with 12 identified as eligible for review. Meta-analysis showed evening light affects sleep latency, sleep efficiency and slow wave sleep, with overall effect sizes (95% confidence interval) of 0.69 (−0.50; 1.88), 0.34 (−0.13; 0.82) and −0.61 (−1.85; 0.62), respectively. Estimated melanopic EDI in the range of 100–1000 lx yielded clear dose–response relationships for sleep latency and sleep efficiency, but not for slow wave sleep. Whilst illuminance and duration indicated no apparent effects for a single evening light exposure on PSG-assessed sleep latency, sleep efficiency and slow wave sleep, we observed evidence for a relationship between light exposure and sleep effects based on melanopic EDI. Hence, melanopic EDI may provide a robust predictor of non-visual responses on human sleep.

ABSTRACT Psychiatric inpatient units often maintain a degree of lighting at night to facilitate the observation of patients, but this has the potential to disrupt sleep. Certain wavelengths of light may be less likely to disturb sleep and if such lighting permitted adequate observations, patient wellbeing may be improved. AIMS AND METHOD: This study explored the effects of changing night‐lights from broad‐band white to narrow‐band red on the amount of sleep observed, ‘as required’ medication administered and number of falls, in an old age psychiatry inpatient setting. Qualitative data was also gathered with a staff questionnaire. We hypothesised that compared to the use of white lights, red lights would be associated with a greater amount of recorded sleep, lesser use of ‘as required’ medication and no increase in the number of falls (reflecting comparable safety). RESULTS: Whilst there were no significant differences in quantitative measures recorded, there were more observations of sleep during the red light period than the white light period (14.1 versus 13.9 times per night) (U = 627.5, z = − 0.69, p = 0.49) and fewer ‘as required’ medication administrations during the red light period compared to the white light period (3.3 versus 4.8 times per night) (U = 640.0, z = 0.56, p = 0.57). Qualitatively, the staff of the organic assessment unit reported that patients were sleeping better and less agitated at night. CLINICAL IMPLICATIONS: Larger and more in‐depth studies are required to examine the full effectiveness of using safe, sleep‐enhancing lighting on wards at night. HIGHLIGHTSIn this small study, the use of red lights at night was compared with white lights.The lighting change was not associated with a significant increase in sleep or a reduction in the use of sedative drugs.Subjectively, staff on an organic assessment unit reported that their patients were sleeping better and less agitated.Lighting can be changed without great expense and this simple intervention should be the subject of further research.

… , improve shift workers' circadian rhythm and improve patients… members' perception of a circadian lighting system (CLS) … pre-existing lighting (PeL) and circadian lighting system (CLS…