面向助眠情境的节律照明产品设计研究

照明在人类生活、工作和学习中发挥着举足轻重的作用, 除了提供基本的视觉作用(对周围事物的大小、颜色、形状等方面的视觉感知)外, 还会对人的生理、心理功能产生显著影响, 如调节褪黑素分泌、影响生物节律, 促进认知加工、调节由季节变化引起的情绪情感障碍(SAD)等。这种对生理、心理活动产生直接或间接的影响即为照明的非视觉作用。近年来, 照明的非视觉作用及其背后的神经机制得到了研究者的广泛关注和大量实证研究, 并取得了丰硕成果。未来研究需从模型建构、动态照明等角度入手进一步探索照明的非视觉作用及其脑神经机制。

目的 探讨星状神经节区光生物调节对乳腺癌患者术后睡眠及疼痛的干预效果。 方法 选取2024年6—12月于保定市第一中心医院择期行全身麻醉下乳腺癌改良根治术的患者114例，年龄18 ~ 65岁，ASA Ⅰ—Ⅲ级，体质量指数18 ~ 30 kg/m2。采用随机数字表法将患者分为对照组（C组）和干预组（T组）。C组患者除常规麻醉操作外，不进行任何干预；T组患者在全身麻醉后接受单次星状神经节区线偏振光照射。照射参数设定为功率80%，照射/间歇周期为2 s/4 s，总时长为40 min。记录两组患者术前1 d（D0）、术后第2天（D2）及术后第5天（D5）的匹兹堡睡眠质量指数（PSQI）评分、总睡眠时间、睡眠效率及夜间觉醒次数，并比较D2时的视觉模拟评分和术后48 h内患者自控镇痛有效按压次数及术后不良事件的发生和患者满意度。 结果 与C组相比，T组患者在D2、D5时的PSQI评分及术后睡眠障碍发生率明显降低（ P < 0.001）；在睡眠客观指标方面，T组患者的总睡眠时间与睡眠效率均显著增加（ P < 0.001），而夜间觉醒次数显著减少（ P < 0.001）。与C组相比，T组在D2的视觉模拟评分显著降低，有效按压次数明显减少（ P < 0.001）；T组恶心呕吐发生率显著降低（ P < 0.001），患者满意度评分显著升高（ P < 0.001）。 结论 星状神经节区光生物调节能有效改善乳腺癌术后患者的睡眠质量，降低术后睡眠障碍发生率，同时有助于减轻术后疼痛，提升患者满意度，且安全性良好。

随着智能建筑与绿色建筑理念的发展，电气照明系统的设计逐渐从单一的照明功能扩展到节能控制与人体舒适度的平衡。传统照明设计在节能与舒适性之间往往难以兼顾，无法满足不同场景下对光照强度、色温、分布均匀性以及动态调节的多样化需求。智能控制系统的引入为照明设计提供了新路径，它通过传感器、控制算法和人机交互界面，实现对照度、色温和光分布的精确调节，并能够依据人的生理节律和视觉心理进行适配。文中通过分析建筑电气照明系统的智能控制设计思路，探讨其在提升能源利用效率与人体舒适度方面的作用，研究多维度调控机制与适配策略，提出优化方案与发展方向。研究结果表明，基于智能控制的电气照明系统不仅能够有效降低能耗，还能改善工作与生活环境，促进人机和谐与建筑功能价值的提升。

目前，在邮轮上大部分的情况是人被动的适应环境。如何把智能环境相关技术与邮轮居住空间设计有机结合起来，让“环境去适应人”从而提高用户的舒适度是本文研究的重点。通过文献归纳和总结，得出邮轮居住空间智能化设计原则；通过对空间布局、光、色彩、温湿度等环境要素的智能控制与人体生理指标的动态适应间的关系进行研究，得出人体生理指标与环境参数间适配的规律；针对某邮轮居住舱室要素进行了智能化设计应用研究，使其环境要素能够根据用户的生理和心理的动态变化做出相应的调整，达到提升乘客居住体验的目的。

光照除了传统的视觉作用外, 还具有一定的非视觉效应, 包括调节昼夜节律、褪黑素分泌和警觉性等生理功能和行为表现。随着光照对生理节律影响研究的不断深入, 近来很多学者开始关注光照的警觉性作用。我们根据最新研究进展总结了：(1)警觉性的测量工具; (2)光照强度、时长、时间点、波长、色温等对光照警觉性作用的影响; (3)光照在治疗情绪障碍、调节生理节律、完善办公照明方面的应用; (4)提出了继续探讨光照警觉性作用的神经机制、优化参数特征和探讨混淆变量的研究方向。

人造光虽然在提高生产效率、丰富夜间生活方面发挥着重要作用，但同时也引发了过度夜间光照这一公共卫生问题。该问题主要表现为对自然光周期的干扰，进而导致人体生物钟紊乱，对睡眠质量、情绪状态以及心血管健康产生负面影响，因此被认定为一种新型的环境污染物。孕妇作为对环境污染高度敏感的群体，其健康状况受到广泛关注。本综述旨在探讨当前夜光暴露的现状、评估方法以及其对孕妇和新生儿可能产生的影响及其潜在机制，以期为预防过度夜光暴露、促进母婴健康提供科学的理论支持。

… circadian rhythm desynchrony and sleep disorders. To explore the effects of different lighting patterns on circadian rhythm and sleep… weeks with one lighting pattern per week. The static …

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 …

Humans live in a 24-hour environment, in which light and darkness follow a diurnal pattern. Our circadian pacemaker, the suprachiasmatic nuclei (SCN) in the hypothalamus, is entrained to the 24-hour solar day via a pathway from the retina and synchronises our internal biological rhythms. Rhythmic variations in ambient illumination impact behaviours such as rest during sleep and activity during wakefulness as well as their underlying biological processes. Rather recently, the availability of artificial light has substantially changed the light environment, especially during evening and night hours. This may increase the risk of developing circadian rhythm sleep–wake disorders (CRSWD), which are often caused by a misalignment of endogenous circadian rhythms and external light–dark cycles. While the exact relationship between the availability of artificial light and CRSWD remains to be established, nocturnal light has been shown to alter circadian rhythms and sleep in humans. On the other hand, light can also be used as an effective and noninvasive therapeutic option with little to no side effects, to improve sleep, mood and general well-being. This article reviews our current state of knowledge regarding the effects of light on circadian rhythms, sleep, and mood.

… the relationship between nighttime sleep quality and a range of circadian, physical and … was the relative potential of these factors to act as predictors of sleep quality in this cohort. …

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.

The regular rise and fall of the sun resulted in the development of 24-h rhythms in virtually all organisms. In an evolutionary heartbeat, humans have taken control of their light environment with electric light. Humans are highly sensitive to light, yet most people now use light until bedtime. We evaluated the impact of modern home lighting environments in relation to sleep and individual-level light sensitivity using a new wearable spectrophotometer. We found that nearly half of homes had bright enough light to suppress melatonin by 50%, but with a wide range of individual responses (0–87% suppression for the average home). Greater evening light relative to an individual’s average was associated with increased wakefulness after bedtime. Homes with energy-efficient lights had nearly double the melanopic illuminance of homes with incandescent lighting. These findings demonstrate that home lighting significantly affects sleep and the circadian system, but the impact of lighting for a specific individual in their home is highly unpredictable.

Exposure to light is an important factor in regulating sleep and sleep quality, especially for elderly people with a high risk of sleep problems. A systematic literature review was conducted to explore the current understanding of the relationship between light and sleep quality of the elderly, and to identify methodological gaps and soundness of existing studies to inform the design of future experimental studies. Specific focus is given to healthcare centres and similar settings due to their controlled environment and the high prevalence of sleep disturbances. Out of 406 publications screened from four databases—namely Google Scholar, Semantic Scholar, Lens.Org, and Scopus—380 studies remained after removing duplicates, and 19 studies published after 2002 that were relevant to the review topic were selected based on the PRISMA 2020 guidelines. The selected studies were analysed using six key aspects, which reflect typical components of experimental design such as participants’ characteristics, experiment and exposure duration, mode of light exposure, lighting and light interventions, experiment procedure, and data collection methods. The results indicated that many studies have limitations in terms of the accuracy and generalisability of findings in representing the entire elderly population due to issues with experimental design or control of the participants’ attendance. The results suggest that future studies should increase the duration of light intervention to around 21–35 days and the number of participants to around 14 and 47. The issues identified from the experimental designs of the selected studies provide valuable insights for establishing guidelines and recommendations for future studies.

We investigated the effectiveness of a lighting intervention tailored to maximally affect the circadian system as a nonpharmacological therapy for treating problems with sleep, mood, and behavior in persons with Alzheimer disease and related dementias (ADRD). This 14-week randomized, placebo-controlled, crossover design clinical trial administered an all-day active or control lighting intervention to 46 patients with ADRD in 8 long-term care facilities for two 4-week periods (separated by a 4-week washout). The study employed wrist-worn actigraphy measures and standardized measures of sleep quality, mood, and behavior. The active intervention significantly improved Pittsburgh Sleep Quality Index scores compared to the active baseline and control intervention (mean ± SEM: 6.67 ± 0.48 after active intervention, 10.30 ± 0.40 at active baseline, 8.41 ± 0.47 after control intervention). The active intervention also resulted in significantly greater active versus control differences in intradaily variability. As for secondary outcomes, the active intervention resulted in significant improvements in Cornell Scale for Depression in Dementia scores (mean ± SEM: 10.30 ± 1.02 at baseline, 7.05 ± 0.67 after active intervention) and significantly greater active versus control differences in Cohen-Mansfield Agitation Inventory scores (mean ± SEM: −5.51 ± 1.03 for the active intervention, −1.50 ± 1.24 for the control intervention). A lighting intervention tailored to maximally entrain the circadian system can improve sleep, mood, and behavior in patients with dementia living in controlled environments. Registry: ClinicalTrials.gov, title: Methodology Issues in a Tailored Light Treatment for Persons With Dementia, URL: https://clinicaltrials.gov/ct2/show/NCT01816152, identifier: NCT01816152. Figueiro MG, Plitnick B, Roohan C, Sahin L, Kalsher M, Rea MS. Effects of a tailored lighting intervention on sleep quality, rest–activity, mood, and behavior in older adults with Alzheimer disease and related dementias: a randomized clinical trial. J Clin Sleep Med. 2019;15(12):1757–1767.

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.

BACKGROUND If patients in the intensive care unit are constantly exposed to artificial light, various problems related to sleep, and circadian rhythm may develop. OBJECTIVES The aim of this study was to determine the effect of light in the ICU on sleep quality and physiological parameters of patients. DESIGN Experimental and randomized-controlled trial. METHODS The study was conducted in the ICU of a training and research hospital between May 2019-March 2021. The patients hospitalized in the ICU constituted the population of the study, and 148 patients constituted the sample calculated by power analysis. In individuals allocated into the experimental and control groups according to randomization, a cyclic lighting system was organized in isolation rooms for the experimental group, and a standard ICU lighting system was used in the control group. RESULTS The durations of deep sleep, light sleep and total sleep in the experimental group were statistically significantly higher compared to the control group (P < .05). No statistically significant difference was found in terms of systolic and diastolic blood pressure, peak heart rate and body temperature values in the experimental and control groups according to 48-hour sleep duration (P > .05). The 48-hour respiratory rate values in the ICU were statistically significantly higher in the control group compared to the experimental group (P < .05). CONCLUSION It was determined that the light in the ICU affected the sleep quality and physiological parameters of individuals. It is recommended to make environmental arrangements for light according to human biorhythm and to reduce exposure to artificial light in order to increase sleep quality and sleep duration in the ICU. TRIAL REGISTRATION NUMBER NCT0466142.

Patients in an intensive care unit (ICU) may risk disruption of their circadian rhythm. In an intervention research project a cycled lighting system was set up in an ICU room to support patients' circadian rhythm. Part I aimed to compare experiences of the lighting environment in two rooms with different lighting environments by lighting experiences questionnaire. The results indicated differences in advantage for the patients in the intervention room (n=48), in perception of daytime brightness (p=0.004). In nighttime, greater lighting variation (p=0.005) was found in the ordinary room (n=52). Part II aimed to describe experiences of lighting in the room equipped with the cycled lighting environment. Patients (n=19) were interviewed and the results were presented in categories: "A dynamic lighting environment", "Impact of lighting on patients' sleep", "The impact of lighting/lights on circadian rhythm" and "The lighting calms". Most had experiences from sleep disorders and half had nightmares/sights and circadian rhythm disruption. Nearly all were pleased with the cycled lighting environment, which together with daylight supported their circadian rhythm. In night's actual lighting levels helped patients and staff to connect which engendered feelings of calm.

Summary Light is a potent circadian entraining agent. For many people, daily light exposure is fundamentally dysregulated with reduced light during the day and increased light into the late evening. This lighting schedule promotes chronic disruption to circadian physiology resulting in a myriad of impairments. Developmental changes in sleep-wake physiology suggest that such light exposure patterns may be particularly disruptive for adolescents and further compounded by lifestyle factors such as early school start times. This narrative review describes evidence that reduced light exposure during the school day delays the circadian clock, and longer exposure durations to light-emitting electronic devices in the evening suppress melatonin. While home lighting in the evening can suppress melatonin secretion and delay circadian phase, the patterning of light exposure across the day and evening can have moderating effects. Photic countermeasures may be flexibly and scalably implemented to support sleep-wake health; including manipulations of light intensity, spectra, duration and delivery modality across multiple contexts. An integrative approach addressing physiology, attitudes, and behaviors will support optimization of light-driven sleep-wake outcomes in adolescents.

In modern society, the average person spends more than 90% of their time indoors. However, despite the growing scientific understanding of the impact of light on biological mechanisms, the existing light in the built environment is designed predominantly to meet visual performance requirements only. Lighting can also be exploited as a means to improve occupant health and well-being through the circadian functions that regulate sleep, mood, and alertness. The benefits of well-lit spaces map across other regularly occupied building types, such as residences and schools, as well as patient rooms in healthcare and assisted-living facilities. Presently, Human Centric Lighting is being offered based on generic insights on population average experiences. In this paper, we suggest a personalized bio-adaptive office lighting system, controlled to emit a lighting recipe tailored to the individual employee. We introduce a new mathematical optimization for lighting schedules that align the 24-h circadian cycle. Our algorithm estimates and optimizes parameters in experimentally validated models of the human circadian pacemaker. Moreover, it constrains deviations from the light levels desired and needed to perform daily activities. We further translate these into general principles for circadian lighting. We use experimentally validated models of the human circadian pacemaker to introduce a new algorithm to mathematically optimize lighting schedules to achieve circadian alignment to the 24-h cycle, with constrained deviations from the light levels desired for daily activities. Our suggested optimization algorithm was able to translate our findings into general principles for circadian lighting. In particular, our simulation results reveal: (1) how energy constrains drive the shape of optimal lighting profiles by dimming the light levels in the time window that light is less biologically effective; (2) how inter-individual variations in the characteristic internal duration of the day shift the timing of optimal lighting exposure; (3) how user habits and, in particular, late-evening light exposure result in differentiation in late afternoon office lighting.

The study investigated the effect of bright blue-enriched versus blue-suppressed indoor light on sleep and wellbeing of healthy participants over 65 years. Twenty-nine participants in 20 private houses in a uniform settlement in Copenhagen were exposed to two light epochs of 3 weeks with blue-enriched (280 lux) and 3 weeks blue-suppressed (240 lux) indoor light or vice versa from 8 to 13 pm in a randomized cross-over design. The first light epoch was in October, the second in November and the two light epochs were separated by one week. Participants were examined at baseline and at the end of each light epoch. The experimental indoor light was well tolerated by the majority of the participants. Sleep duration was 7.44 (95% CI 7.14–7.74) hours during blue-enriched conditions and 7.31 (95% CI 7.01–7.62) hours during blue-suppressed conditions (p = 0.289). Neither rest hours, chromatic pupillometry, nor saliva melatonin profile showed significant changes between blue-enriched and blue-suppressed epochs. Baseline Pittsburgh Sleep Quality Index (PSQI) was significantly worse in females; 7.62 (95% CI 5.13–10.0) versus 4.06 (95% CI 2.64–5.49) in males, p = 0.009. For females, PSQI improved significantly during blue-enriched light exposure (p = 0.007); no significant changes were found for males. The subjective grading of indoor light quality doubled from participants habitual indoor light to the bright experimental light, while it was stable between light epochs, although there were clear differences between blue-enriched and blue-suppressed electrical light conditions imposed. Even though the study was carried out in the late autumn at northern latitude, the only significant difference in Actiwatch-measured total blue light exposure was from 8 to 9 am, because contributions from blue-enriched, bright indoor light were superseded by contributions from daylight.

Sleep and circadian rhythm are reported to be severely abnormal in critically ill patients. Disturbed sleep can lead to the development of delirium and, as a result, can be associated with prolonged stay in the intensive care unit (ICU) and increased mortality. The standard criterion method of sleep assessment, polysomnography (PSG), is complicated in critically ill patients due to the practical challenges and interpretation difficulties. Several PSG sleep studies in the ICU reported the absence of normal sleep characteristics in many critically ill patients, making the standard method of sleep scoring insufficient in this patient group. Watson et al proposed a modified classification for sleep scoring in critically ill patients. This classification has not yet been validated. Sleep disturbance in the ICU is a multifactorial problem. The ICU environment, mechanical ventilation, medication, as well as the critical illness itself have been reported as important sleep disturbing factors. Secretion of sleep hormone, melatonin, expressing circadian rhythmicity was found abolished or phase delayed in critically ill patients. Various interventions have been tested in several studies aiming to improve sleep quality and circadian rhythm in the ICU. The results of these studies were inconclusive due to using the sleep assessment methods other than PSG or the absence of a reliable sleep scoring tool for the analysis of the PSG findings in this patient population. Development of a valid sleep scoring classification is essential for further sleep research in critically ill patients.

… lighting has been beneficial to society, but unnecessary light … -night bedside light can affect sleep quality and brain activity. … Light is the major synchronizer of circadian rhythm for a …

AIM Elderly multimorbid care home dwellers are a heterogenic group of frail individuals that exhibit sleep disturbances and a range of co-morbidities. The project aimed to study the possible effect of indoor circadian-adjusted LED-lighting (CaLED) in the elderly residents' care home on their sleeping patterns and systemic biomarkers associated with inflammation. METHODS A 16-week trial study was performed to follow the intervention and control groups using the Pittsburgh Sleep Quality Index (PSQI) and Epworth Sleepiness Scale (ESS) to monitor sleep and daytime sleepiness, and biomarkers IL-6, TNF-α and suPAR, to estimate the levels of inflammation. RESULTS There was no significant impact on sleep improvement after the short intervention time when analyzing the PSQI and ESS results. However, we found several challenges using these tools for this specific group of individuals. Thus, important knowledge was gained for future studies in elderly care home dwellers. The inflammation state throughout the entire study period was stable for most of the elderly and no significant change was detected from before to after the intervention. This study represents a first-to-date attempt to ameliorate the adverse effects of sleep disturbances that characterize a randomly chosen group of elderly multimorbid subjects, by using circadian-adjusted LED-lighting in a natural care home environment. CONCLUSION In this pragmatic randomized study of home dwelling individuals we were not able to demonstrate an improved sleep pattern as judged by PSQI, ESS or a change in inflammatory state.

Artificial lighting is omnipresent in contemporary society with disruptive consequences for human sleep and circadian rhythms because of overexposure to light, particularly in the evening/night hours. Recent evidence shows large individual variations in circadian photosensitivity, e.g. melatonin suppression, due to artificial light exposure. Despite the emerging body of research indicating that the effects of light on sleep and circadian rhythms vary dramatically across individuals, recommendations for appropriate light exposure in real-life scenarios rarely consider such individual effects. This review addresses recently identified links between individual traits, e.g. age, sex, chronotype, genetic haplotypes, and the effects of evening/night light on sleep and circadian hallmarks, based on human laboratory and field studies. Target biological mechanisms for individual differences in light sensitivity include differences occurring within the retina and downstream, such as the central circadian clock. This review also highlights that there are wide gaps of uncertainty, despite the growing awareness that individual differences shape the effects of evening/night light on sleep and circadian physiology. These include i. why do certain individual traits differentially affect the influence of light on sleep and circadian rhythms; ii. What is the translational value of individual differences in light sensitivity in populations exposed to light at night, such as night shift workers; and iii. What is the magnitude of individual differences in light sensitivity in large population-based studies? Collectively, the current findings provide strong support for considering individual differences when defining optimal lighting specifications, thus allowing for personalized lighting solutions that promote quality of life and health.

This narrative review synthesizes interdisciplinary evidence on how indoor environmental factors, thermal conditions, lighting, noise, and air quality affect sleep quality and evaluates interventions to optimize these factors in energy‐efficient buildings. We analyzed peer‐reviewed studies (2000–2024) from Web of Science, ScienceDirect, PubMed, Scopus, and Wiley, selected through a structured screening process focusing on human studies in nonclinical settings. Evidence synthesis suggests that (1) moderate thermal environments, generally ranging between 18°C and 22°C, support sleep continuity in most healthy adults, though optimal thresholds may vary by age, region, and season. (2) Evening exposure to short‐wavelength blue light, typically above 30–50 lux at 460–480 nm, disrupts circadian timing, particularly in adolescents and sensitive populations. (3) Nighttime noise levels above ~35 dB (A) are linked to rapid eye movement (REM) sleep disruption, with sensitivity varying by individual and noise source. (4) PM2.5 and CO2 accumulation in poorly ventilated bedrooms contribute to increased sleep fragmentation. Strategies like broadened HVAC setpoints and nighttime ventilation offer energy‐saving potential without compromising sleep quality, but empirical support is sparse. Promising interventions, including dynamic lighting, acoustic insulation, and intelligent ventilation, need further validation in real‐world settings. This review highlights the need for sleep‐centric building standards and policies that prioritize both occupant health and energy efficiency. Future research should focus on personalized interventions and longitudinal studies to address mechanistic gaps.

Sleep is an essential physiological process, and residential lighting environments significantly impact sleep quality. To address circadian phase delays exacerbated by pre-sleep smartphone use in youth, this study developed targeted lighting interventions. Through laboratory simulations, the effects of color temperature, illuminance, and horizontal blue light ratio on multisensory responses (visual, psychological, physiological) and sleep quality were examined. A rhythmic lighting strategy for healthy environments was proposed. Key findings: (1) Lighting factors revealed a hierarchy of influence on sleep quality—color temperature had the greatest influence on sleep quality, followed by illuminance and horizontal blue light ratio. Optimal conditions include cycling color temperature, 800 lx illuminance, and 25% blue light ratio. (2) Context-specific interventions were proposed—high illuminance with low color temperature enhances comfort in healthcare/leisure spaces, while medium–high color temperature, high illuminance, and cycling blue light ratios improve efficiency in office/study environments. (3) A time-sequenced rhythmic lighting scheme aligned with daily routines was implemented. This study establishes a novel health evaluation framework for residential lighting, combining sleep quality, psychological, and physiological metrics, redefines research paradigms for light-induced health effects, and provides actionable insights for optimizing workplace lighting.

In our fast-paced and ever-evolving world, the importance of obtaining high-quality rest cannot be overstated. The repercussions of inadequate sleep patterns, such as insomnia, stress, and chronic health conditions, have become increasingly evident. In response to these challenges and a commitment to promoting overall health, this initiative aims to harness the potential of Internet of Things (IoT) technology to create a sophisticated sleeping environment. The envisioned smart bedroom will dynamically adapt to the user's surroundings, ultimately leading to an enhancement of sleep quality and an overall boost in well-being. This research is focused on developing an intelligent bedroom utilizing IoT technology to improve sleep quality and bolster general health which aligns seamlessly with the United Nations Sustainable Development Goal (SDG) 3 - “Ensuring Health and Promoting Well-being.” SDG 3 emphasizes the pursuit of robust health and the nurturing of overall well-being for individuals of all age groups. By integrating IoT technology with a specific focus on enhancing sleep quality and overall health, this initiative not only addresses immediate healthcare needs but also makes a substantial contribution to the broader global mission of advancing health and well-being, following the principles of SDG 3.

With the rising attention towards improving the quality of life and mental health, sleep hygiene and sleep quality have recently been the main topics of numerous studies. Quality of sleep not only affects our physical status but also plays a pivotal role in our psychological and emotional states. Sleep deprivation can increase the risk of cardiovascular and metabolic diseases along with the risk of impaired concentration and consequent road injury and accidents. As technology has become a main figure in our daily lives, technological advances have paid a great interest in improving the quality of sleep by enhancing the detection of sleep-related disorders and sleep abnormalities, particularly in the setting of smart homes and the Internet of Things (IoT). Smartphone applications, portable wearable gadgets, and devices along with more sophisticated and precise algorithms are now endeavoring to help us improve our quality of sleep and subsequently our quality of life. Hence, this review aims to illustrate a vivid picture of recent advancements in smart homes and their related technologies for improving sleep quality.

Background Typical hospital lighting is rich in blue-wavelength emission, which can create unwanted circadian disruption in patients when exposed at night. Despite a growing body of evidence regarding the effects of poor sleep on health outcomes, physiologically neutral technologies have not been widely implemented in the US healthcare system. Objective The authors sought to determine if rechargeable, proximity-sensing, blue-depleted lighting pods that provide wireless task lighting can make overnight hospital care more efficient for providers and less disruptive to patients. Design Non-randomised, controlled interventional trial in an intermediate-acuity unit at a large urban medical centre. Methods Night-time healthcare providers abstained from turning on overhead patient room lighting in favour of a physiologically neutral lighting device. 33 nurses caring for patients on that unit were surveyed after each shift. 21 patients were evaluated after two nights with standard-of-care light and after two nights with lighting intervention. Results Providers reported a satisfaction score of 8 out of 10, with 82% responding that the lighting pods provided adequate lighting for overnight care tasks. Among patients, a median 2-point improvement on the Hospital Anxiety and Depression Scale was reported. Conclusion and relevance The authors noted improved caregiver satisfaction and decreased patient anxiety by using a blue-depleted automated task-lighting alternative to overhead room lights. Larger studies are needed to determine the impact of these lighting devices on sleep measures and patient health outcomes like delirium. With the shift to patient-centred financial incentives and emphasis on patient experience, this study points to the feasibility of a physiologically targeted solution for overnight task lighting in healthcare environments.

Noise and light levels during hospitalizations can disrupt sleep and circadian health, resulting in worsened health outcomes. This study describes patterns of noise and light for inpatient children undergoing stem cell transplants. Objective meters tracked noise and light levels every minute for 6 months. Median overnight sound was 55dB (equivalent to conversational speech). There were 3.4 loud noises (>80dB) per night on average. Children spent 62% of the 24-hour cycle in non-optimal lighting, with daytime light dimmer than recommended 98% of the time. Over the 6-month period, the lowest overnight noise level recorded exceeded World Health Organization recommendations for sleep, with frequent spikes into ranges known to cause wakings. During the day, children were rarely exposed to light sufficient to preserve healthy circadian rhythms. Hospitals should address systematic environmental and workflow disruptors to improve the sleep and circadian health of patients, particularly those already at elevated risk for health morbidities.

Electric lighting has decreased dependence on natural light to illuminate the workplace. Humans are genetically predisposed to be day-oriented (diurnal) and depend on daylight to regulate circadian rhythms. Shift work will force workers to sleep and work at non-biological times, inducing circadian disruption with implications for workers’ safety and health. The scientific literature may be used in practice in shift work settings to improve safety, performance and health in the workplace by reducing circadian misalignment. Alertness profiles at work and degree of melatonin suppression may indicate degree of circadian disruption among workers. However, when considering lighting solutions at night, there are several factors that need consideration. Light measures based on biological effectiveness should be used rather than room illuminance giving better predictions of performance and long-term health among workers. Also, large individual differences in light sensitivity and preferences suggest not only to rely on common lighting alone but also to implement complementary individual lighting solutions at work. Lighting advice should consider shift scheduling characteristics such as speed of turnover and shift timing to guide decisions of preferred circadian phase influence. Lighting should also include the flexibility to be fit for morning, afternoon and evening work.

… specifically designed to promote a sleep-friendly hospital … institutions reported having no sleep-friendly practices in place… exposed to a cyclic lighting system simulating natural light …

… melatonin production in humans and animals caused by environmental lighting, especially short wavelength lighting … light may prevent the suppression of melatonin, which could help to …

Light‐induced melatonin suppression in children is reported to be more sensitive to white light at night than that in adults; however, it is unclear whether it depends on spectral distribution of lighting. In this study, we investigated the effects of different color temperatures of LED lighting on children's melatonin secretion during the night. Twenty‐two healthy children (8.9 ± 2.2 years old) and 20 adults (41.7 ± 4.4 years old) participated in this study. A between‐subjects design with four combinations, including two age groups (adults and children) and the two color temperature conditions (3000 K and 6200 K), was used. The experiment was conducted for two consecutive nights. On the first night, saliva samples were collected every hour under a dim light condition (<30 lx). On the second night, the participants were exposed to either color temperature condition. Melatonin suppression in children was greater than that in adults at both 3000 K and 6200 K condition. The 6200 K condition resulted in greater melatonin suppression than did the 3000 K condition in children (P < 0.05) but not in adults. Subjective sleepiness in children exposed to 6200 K light was significantly lower than that in children exposed to 3000 K light. In children, blue‐enriched LED lighting has a greater impact on melatonin suppression and it inhibits the increase in sleepiness during night. Light with a low color temperature is recommended at night, particularly for children's sleep and circadian rhythm.

… suppressing nocturnal melatonin than monochromatic blue light matched for melanopsin stimulation, implying that the melatonin suppression … composition of polychromatic lights for use …

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.

Artificial light at night can be harmful to the environment, and interferes with fauna and flora, star visibility, and human health. To estimate the relative impact of a lighting device, its radiant power, angular photometry and detailed spectral power distribution have to be considered. In this paper we focus on the spectral power distribution. While specific spectral characteristics can be considered harmful during the night, they can be considered advantageous during the day. As an example, while blue-rich Metal Halide lamps can be problematic for human health, star visibility and vegetation photosynthesis during the night, they can be highly appropriate during the day for plant growth and light therapy. In this paper we propose three new indices to characterize lamp spectra. These indices have been designed to allow a quick estimation of the potential impact of a lamp spectrum on melatonin suppression, photosynthesis, and star visibility. We used these new indices to compare various lighting technologies objectively. We also considered the transformation of such indices according to the propagation of light into the atmosphere as a function of distance to the observer. Among other results, we found that low pressure sodium, phosphor-converted amber light emitting diodes (LED) and LED 2700 K lamps filtered with the new Ledtech’s Equilib filter showed a lower or equivalent potential impact on melatonin suppression and star visibility in comparison to high pressure sodium lamps. Low pressure sodium, LED 5000 K-filtered and LED 2700 K-filtered lamps had a lower impact on photosynthesis than did high pressure sodium lamps. Finally, we propose these indices as new standards for the lighting industry to be used in characterizing their lighting technologies. We hope that their use will favor the design of new environmentally and health-friendly lighting technologies.

We compared the effects of bedroom-intensity light from a standard fluorescent and a blue- (i.e., short-wavelength) depleted LED source on melatonin suppression, alertness, and sleep. Sixteen healthy participants (8 females) completed a 4-day inpatient study. Participants were exposed to blue-depleted circadian-sensitive (C-LED) light and a standard fluorescent light (FL, 4100K) of equal illuminance (50 lux) for 8 h prior to a fixed bedtime on two separate days in a within-subject, randomized, cross-over design. Each light exposure day was preceded by a dim light (<3 lux) control at the same time 24 hours earlier. Compared to the FL condition, control-adjusted melatonin suppression was significantly reduced. Although subjective sleepiness was not different between the two light conditions, auditory reaction times were significantly slower under C-LED conditions compared to FL 30 minutes prior to bedtime. EEG-based correlates of alertness corroborated the reduced alertness under C-LED conditions as shown by significantly increased EEG spectral power in the delta-theta (0.5–8.0 Hz) bands under C-LED as compared to FL exposure. There was no significant difference in total sleep time (TST), sleep efficiency (SE%), and slow-wave activity (SWA) between the two conditions. Unlike melatonin suppression and alertness, a significant order effect was observed on all three sleep variables, however. Individuals who received C-LED first and then FL had increased TST, SE% and SWA averaged across both nights compared to individuals who received FL first and then C-LED. These data show that the spectral characteristics of light can be fine-tuned to attenuate non-visual responses to light in humans.

Evening residential illumination possesses the capacity to impair sleep quality via the suppression of endogenous melatonin production, a process largely driven by short-wavelength (blue) light. In this investigation, we characterized the light emissions from 52 distinct examples across three common lamp technologies: light-emitting diodes (LED), incandescent, and compact fluorescent (CFL) lamps. To estimate the differential circadian impact of these sources, we determined the Melatonin Suppression Value (MSV), melanopic illuminance, and photopic illuminance for each. Our findings reveal that “cool” white LED (median 12.3% MSV) and “cool” white CFL (12.1% MSV) lamps induce considerably greater melatonin suppression than “warm” white LED (3.6%), “warm” white CFL (2.6%), or traditional incandescent (1.5%) lamps. As potential countermeasures, we examined the efficacy of tunable Correlated Color Temperature (CCT) lamps and “blue-light–filtering” (BLF) lenses. The four tunable LED lamps demonstrated a profound ability to mitigate circadian disruption, reducing estimated melatonin suppression from 10% at a 5700 K (cool white) setting to 0.1% at 2100 K (warm white). An analysis of eight BLF lenses identified variable performance; while six had moderate impacts compared to uncorrected vision, their benefit was limited relative to standard clear lenses. Only two BLF lenses, distinguished by a “brown” tint, proved highly effective, reducing estimated suppression to below 0.3%. These results suggest that cool white CFL and LED lamps may exert a greater disruptive influence on sleep physiology than other lamp types. Conversely, tunable lamps adjusted to warm settings and “brown”-tinted BLF lenses represent beneficial strategies for ameliorating this effect. (Detailed measurement methodologies are available in a previously published study, with supplementary calculations provided separately).

… Because we did not strictly control the lighting condition during daytime in the present study, exposure to natural bright light such as sunlight during the daytime might have diminished …

… melatonin suppression with different polychromatic light sources [fluorescent lamps] found significant melatonin suppression with … of light-induced melatonin suppression. Light-induced …

Five intensities of artificial light were examined for the effect on nocturnal melatonin concentrations. Maximum suppression of melatonin following 1 hr of light at midnight was 71%, 67%, 44%, 38%, and 16% with intensities of 3,000, 1,000, 500, 350, and 200 lux (lx), respectively. In contrast to some previous reports, light of 1,000 lx intensity was sufficient to suppress melatonin to near daytime levels, and intensities down to 350 lx were shown to significantly suppress nocturnal melatonin levels below prelight values. On the basis of these data, it is suggested that when examining the melatonin sensitivity of patient groups (such as bipolar affective disorders) to artificial light, an appropriate light intensity should be established in each laboratory. Light of less intensity (e.g., 200–350 lx) may be more suitable to dichotomize patient groups from control subjects.

Studies with monochromatic light stimuli have shown that the action spectrum for melatonin suppression exhibits its highest sensitivity at short wavelengths, around 460 to 480 nm. Other studies have demonstrated that filtering out the short wavelengths from white light reduces melatonin suppression. However, this filtering of short wavelengths was generally confounded with reduced light intensity and/or changes in color temperature. Moreover, it changed the appearance from white light to yellow/orange, rendering it unusable for many practical applications. Here, we show that selectively tuning a polychromatic white light spectrum, compensating for the reduction in spectral power between 450 and 500 nm by enhancing power at even shorter wavelengths, can produce greatly different effects on melatonin production, without changes in illuminance or color temperature. On different evenings, 15 participants were exposed to 3 h of white light with either low or high power between 450 and 500 nm, and the effects on salivary melatonin levels and alertness were compared with those during a dim light baseline. Exposure to the spectrum with low power between 450 and 500 nm, but high power at even shorter wavelengths, did not suppress melatonin compared with dim light, despite a large difference in illuminance (175 vs. <5 lux). In contrast, exposure to the spectrum with high power between 450 and 500 nm (also 175 lux) resulted in almost 50% melatonin suppression. For alertness, no significant differences between the 3 conditions were observed. These results open up new opportunities for lighting applications that allow for the use of electrical lighting without disturbance of melatonin production.

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 sensitive to short-wavelength (blue) light than adults (32–51 years). Twenty-four participants (12 adolescents, 12 adults) were exposed to three lighting conditions during successive 4-h study nights that were separated by at least one week. In addition to a dim light (<5 lux) control, participants were exposed to two light spectra (warm (2700 K) and cool (5600 K)) delivering a circadian stimulus of 0.25 at eye level. Repeated measures analysis of variance revealed a significant main effect of exposure duration, indicating that a longer duration exposure suppressed melatonin to a greater degree. The analysis further revealed a significant main effect of spectrum and a significant interaction between spectrum and participant age. For the adolescents, but not the adults, melatonin suppression was significantly greater after exposure to the 5600 K intervention (43%) compared to the 2700 K intervention (29%), suggesting an increased sensitivity to short-wavelength radiation. These results will be used to extend the model of human circadian phototransduction to incorporate factors such as exposure duration and participant age to better predict effective circadian stimulus.

… (<SO0 lux) lighting. In man, room lighting clearly did not suppress secretion at night (15) … , we had developed insensitivity to the artificial lighting conditions ‘we impose upon ourselves. …

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.

Bright nocturnal light has been known to suppress melatonin secretion. However, bright light exposure during the day-time might reduce light-induced melatonin suppression (LIMS) at night. The effective proportion of day-time light to night-time light is unclear; however, only a few studies on accurately controlling both day- and night-time conditions have been conducted. This study aims to evaluate the effect of different day-time light intensities on LIMS. Twelve male subjects between the ages of 19 and 23 years (mean ± S.D., 20.8 ± 1.1) gave informed consent to participate in this study. They were exposed to various light conditions (<10, 100, 300, 900 and 2700 lx) between the hours of 09:00 and 12:00 (day-time light conditions). They were then exposed to bright light (300 lx) again between 01:00 and 02:30 (night-time light exposure). They provided saliva samples before (00:55) and after night-time light exposure (02:30). A one-tailed paired t test yielded significant decrements of melatonin concentration after night-time light exposure under day-time dim, 100- and 300-lx light conditions. No significant differences exist in melatonin concentration between pre- and post-night-time light exposure under day-time 900- and 2700-lx light conditions. Present findings suggest the amount of light exposure needed to prevent LIMS caused by ordinary nocturnal light in individuals who have a general life rhythm (sleep/wake schedule). These findings may be useful in implementing artificial light environments for humans in, for example, hospitals and underground shopping malls.

… however, we cannot conclude that the light sensitivity in terms of melatonin suppression of … room lights used at home (300-500 lx) had almost no effect on the nocturnal melatonin level, …

… light will cause 50% of the melatonin suppressive effect induced by exposure to 10,000 lux, 1 … measured by acute melatonin suppression and phase shifting of dim light melatonin onset (…

This article appears in The Journal of Clinical Endocrinology &amp; Metabolism, published December 30, 2010, 10.1210/jc.2010-2098

OBJECTIVES Because light can regulate sleep rhythms, numerous studies have investigated whether light therapy can improve sleep disorders in older people, but its efficacy remains controversial. Therefore, this systematic review aimed to examine and summarize current evidence about the efficacy of light therapy to improve sleep for older people in residential long-term care. DESIGN Systematic review. SETTING AND PARTICIPANTS Older people living in long-term care settings. METHODS Systematic searches were conducted in the databases PubMed, Web of Science, Cochrane, EMBASE, CINAHL, China National Knowledge Infrastructure, China Science and Technology Journal Database, WanFang, Chinese Biomedical Literature Database, and in reference lists within relevant articles. Studies were eligible for inclusion if they evaluated light therapy for older people with sleep disorders in long-term care settings. RESULTS This systematic review includes 21 articles, summarizing light therapy with different durations and intensities. The light intervention was typically administered between 7:00 and 12:00 am for 30-120 minutes. The interventions lasted from 1 week to several months, and the intensity of the light intervention usually ranged from 2500 to 10,000 lux. Short-term exposure (30-60 minutes) with high light levels (≥10,000 lux), relatively long-term exposure (1-2 hours) with moderate light levels (2500-10,000 lux), or long-term exposure (1-4 hours or full day) with low light levels (≤2500 lux) were associated with improved sleep indicators for older people in long-term care settings. CONCLUSIONS AND IMPLICATIONS The efficacy of light therapy in long-term care settings may be affected by the duration of exposure, time and length of intervention, intensity of light, and equipment used to administer the therapy. Further research must be conducted to optimize light therapy parameters. Large, high-quality randomized controlled trials are needed to deepen our understanding of the effects of light therapy on sleep in older people living in long-term care settings.

… -wake is misaligned with the patient’s circadian system or the external environment, resulting … light can reset the timing of sleep and wake to the desired times, and improve sleep quality …

… help us to see by differentiating contrast in lighting and colors, respectively, ipRGCs send a … In that valley, a display manufacturer typically designs to have the best separation between …

Aims: Interruption of sleep-wake behavioural patterns and circadian rhythms has been associated with the development and worsening of a range of mental health disorders, including depression, bipolar disorder, and schizophrenia, and specific high-risk outcomes such as aggression and suicidality. In full knowledge of the above, we aimed to improve patients’ self-reported sleep quality in an acute male ward, by 20% by the end of January 2025. Methods: An initial survey was conducted for patients to rate their sleep quality on a Numeric Rating Scale (1–10, where 1 = a worst night sleep and 10 = a best night sleep). This survey included close- and open-ended questions for patients to identify perceived barriers to good sleep. Responses were collected over one week from all consenting patients on the ward (10/18 patients). Insights from the survey were used to design targeted interventions addressing the key contributors to poor sleep. These interventions included: a) Offering earplugs to patients; b) Posters with QR codes for a free white noise app to mask disruptive noises; c) Sleep hygiene education through leaflets, with practical tips to improve sleep. A following survey was conducted after two weeks to measure the results of our interventions. Results: Initial survey results included: a) 6/10 median sleep rating reported by our patients, pre-intervention; b) 5/10 of our patients reported their sleep to be disturbed by noise on the ward; c) none of our patients reported sleep to be disturbed by the temperature or lighting of the room; d) 2/10 reported psychiatric symptoms such as auditory hallucinations to disturb their sleep. Results after interventions included: a) all of our patients stated that they received the sleep hygiene booklet, were counselled about the tips, and saw the posters around the ward; b) 11/16 included in the post-intervention survey reported that they found the tips useful; c) 10/16 had used the earplugs and 7/10 of these had found them helpful; d) 1/16 downloaded and used the white noise app; e) 7/10 median sleep rating was reported post-intervention. Conclusion: Non-pharmacological interventions such as earplugs and sleep hygiene education proved to be effective in improving patients’ quality of sleep. The development of a standardized protocol that includes these sleep-friendly practices has been implemented on the ward. Methods’ limitations such as baseline sleep medications and the complexity of contributing factors were taken into consideration.

… Start by designing a sleep-friendly bedroom: opt for blackout curtains … Lighting is a critical aspect of creating a sleep-friendly environment that often gets overlooked. The kind of lighting …

The transition from non‐rapid eye movement (NREM) to rapid eye movement (REM) sleep is considered a transitional or intermediate stage (IS), characterised by high amplitude spindles in the frontal cortex and theta activity in the occipital cortex. Early reports in rats showed an IS lasting from 1 to 5 s, but recent studies suggested a longer duration of this stage of up to 20 s. To further characterise the IS, we analysed its spectral characteristics on electrocorticogram (ECoG) recordings of the olfactory bulb (OB), primary motor (M1), primary somatosensory (S1), and secondary visual cortex (V2) in 12 Wistar male adult rats. By comparing the IS with consolidated NREM/REM epochs, our results reveal that the IS has specific power spectral patterns that fall out of the NREM and REM sleep state power distribution. Specifically, the main findings were that sigma (11–16 Hz) power in OB, M1, S1, and V2 increased during the IS compared with NREM and REM sleep, which started first in the frontal part of the brain (OB −54 s, M1 −53 s) prior to the last spindle occurrence. The beta band (17–30 Hz) power showed a similar pattern to that of the sigma band, starting −54 s before the last spindle occurrence in the M1 cortex. Notably, sigma infraslow coupling (~0.02 Hz) increased during the IS but occurred at a slower frequency (~0.01 Hz) compared with NREM sleep. Thus, we argue that the NREM to REM transition contains its own local spectral profile, in accordance with previous reports, and is more extended than described previously.

BACKGROUND AND OBJECTIVES In standard practice, sleep is classified into distinct stages by human observers according to specific rules as for instance specified in the AASM manual. We here show proof of principle for a conceptualization of sleep stages as attractor states in a nonlinear dynamical system in order to develop new empirical criteria for sleep stages. METHODS EEG (single channel) of two healthy sleeping participants was used to demonstrate this conceptualization. Firstly, distinct EEG epochs were selected, both detected by a MLR classifier and through manual scoring. Secondly, change point analysis was used to identify abrupt changes in the EEG signal. Thirdly, these detected change points were evaluated on whether they were preceded by early warning signals. RESULTS Multiple change points were identified in the EEG signal, mostly in interplay with N2. The dynamics before these changes revealed, for a part of the change points, indicators of generic early warning signals, characteristic of complex systems (e.g., ecosystems, climate, epileptic seizures, global finance systems). CONCLUSIONS The sketched new framework for studying critical transitions in sleep EEG might benefit the understanding of individual and pathological differences in the dynamics of sleep stage transitions. Formalising sleep as a nonlinear dynamical system can be useful for definitions of sleep quality, i.e. stability and accessibility of an equilibrium state, and disrupted sleep, i.e. constant shifting between instable sleep states.