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Today, 16th May, we celebrate UNESCO's International Day of Light, highlighting the crucial role light plays in our health, happiness and well-being. Good light (daylight or electric light that mimics daylight) is essential for good sleep. But if you think you need darkness for better sleep quality, you are completely right. You need darkness at night. But you also need bright light during the day. Daylight is the best! Consider yourself sitting in a dimly lit room during the afternoon for around half an hour. How would you feel? •             A: Bright, active and full of attention •             B: Awake, but not very alert •             C: Sleepy, hard to keep my eyes open Did you answer not very alert, or even sleepy? So, this is what a lack of light can do to your brain! With more daytime light you feel active and you sleep better at night. So, if you want to improve your sleep, focus on the right light at the right time. Here are 4 simple rules: 1.           Go outside during daytime as much as possible 2.           Use bright light in the morning 3.           Dim your lights towards dinner 4.           Make the night as dark as possible

The International Association of Lighting Designers (IALD) is an internationally recognized organization that supports a network of 1,500 independent lighting design professionals who satisfy its rigorous qualification process. The IALD sets the global standard for lighting design excellence by promoting the advancement and recognition of professional lighting designers. Since 1969, it has advanced the lighting design profession worldwide through leadership and advocacy and serves its members by facilitating education, community, and engagement. "The International Association of Lighting Designers is honored to partner with the Good Light Group in this vital effort,” says Christopher Knowlton, Chief Executive Officer of the IALD. “Together, our organizations are deeply committed to promoting the power of quality lighting design to enhance lives and create a more sustainable future. Through this collaboration, we can amplify our vision and significantly impact the built environment to benefit all humankind."

Last week marked our 19th Good Light Group meeting. We began with a brief update on the progress of the Good Light Group by Jan Denneman. Following this presentations by Roger Sexton, Peter Raynham, and Dave Hollingsbee, concluding with a Q&A session. Research into the acceptance and effectiveness of task lighting for non-image forming effects of light A practical experiment concerning in-workplace task-lighting designed by UCL and executed by Stoane Lighting. The effect on 30 participants of using the 2022 recommendations from Brown et al on mood, alertness and sleep are explored. Roger Sexton, Stoane Lighting covered the background: why is practical in-workspace research needed to complement more disciplined laboratory research. What were the research goals and what apparatus did we make especially for it. Professor Peter Raynham, Emeritus Professor of the Lit Environment, UCL Institute for Environmental Design and Engineering (IEDE) covered his experiment design and went through the results and his analysis. Dave Hollingsbee, Managing Director Stoane Lighting showcased the product developed as a result of the research. ·        Watch the Good Light Group news. ·        Watch the introduction by Roger Sexton ·        Watch the results and analysis by Peter Raynham ·        Watch the product presentation by Dave Hollingsbee ·        Watch the Q&A

On April 16th, our group, in collaboration with the Society for Light Treatment and Biological Rhythms (SLTBR), the Daylight Academy (DLA), and Luger Research (LR), organized and presented the 'deLIGHTed Talks - Time Matters - Shining Light on Metabolic Health' lectures. Introduction Welcome, Introduction by Charna Dibner, Geneva University Charna Dibner, moderator of deLIGHTed Talks 7, provides a brief introduction of the Daylight Academy and our circadian clocks, explaining how they work, what happens if they malfunction, and how they are measured. Watch the introduction ​ From the Real World to the Lab: Why Light Matters for Metabolic Health By Kathryn Reid, Professor at Northwestern University Feinberg School of Medicine in the Division of Sleep Medicine. From the Real World to the Lab: Why Light Matters for Metabolic Health The impact of light is dependent on when it occurs relative to the internal biological clock, and as such the timing of when we get light or dark across 24-hours matters. Light exposure patterns are a modifiable factor that can have significant impact on health and wellbeing. Results from real world and laboratory-controlled studies that examine the impact of light exposure on health will be discussed. From pregnant women to older adults, data from real-world monitoring of light levels suggests that higher levels of light exposure in the few hours before and during sleep are associated with poor metabolic health. Watch this presentation ​ Diabetes in the daylight: metabolic benefits through natural office lighting? By Jan-Frieder Harmsen, since 2023, he is working as a postdoctoral researcher in the Healthy Living Spaces Lab at the University Hospital at RTWH Aachen UniversityRTWH Aachen University. Dr. Harmsen talks about a recently completed study, in which he tested if natural daylight during office hours is more beneficial for metabolic health outcomes of type 2 diabetes patients compared to constant artificial lighting. Watch this presentation ​ Panel discussion Including Q&A with the Audience Panelists: Kathryn Reid & Jan-Frieder Harmse Moderation: Charna Dibner Watch the panel discussion

Tone Elise Henriksen Tone Elise Henriksen is a Science Advisor of the Good Light Group. She works as a consultant psychiatrist at Valen Hospital and postdoctoral fellow at the Department of Research and Innovation, Fonna Health Trust, Norway. Right light at the right time is health-promoting and important for all people, but possibly even more so for people with psychiatric disorders. Light during daytime activates the brain and rest of the body at a time we are adapted to be active and awake. To seek light during the day also helps reinforce our circadian rhythms to be synchronised both internally and with the natural 24-hour light/dark cycle of the environment. Light at night promotes activity and wake when the body should rest. Also, light at night has the potential to disrupt the circadian rhythms by sending the wrong daytime signal to the brain’s master-clock. This may happen even if you are sleeping with your eyes shut. The to-date largest naturalistic study on day and night light exposure and the associations with psychiatric disorders, published in Nature Mental Health in 2023, used data from impressive 86 722 participants (from the UK biobank). The paper describes how various levels of light exposure in individuals in free-living conditions are associated with the incidence of a broad span of psychiatric disorders. The authors found that more light exposure during the night was associated with increased self-reporting of the most common and debilitating psychiatric disorders, major depressive disorder, bipolar disorder, post traumatic stress disorder (PTSD), generalized anxiety disorder, psychosis, and self-harm behavior. Higher daytime light-exposure was associated with less reported major depressive disorder, PTSD, psychosis, and self-harm behavior. Moreover, recordings of darker days and brighter nights were associated with poorer mood and well-being.  The strongest associations were found in the brightest night-time light group with a near 30% higher risk of reporting major depressive disorder and self-harm behavior. The authors also found that the day and night light conditions contributed independently and additive to the altered risks of the psychiatric disorder syndromes. Photo by Jongsun Lee on Unsplash The one-week recordings were made with a wrist-worn combined activity and light-recorder in the period 2013-2015. It is of note that the study population was on average 62 years. This means that the participants were middle-aged adults before they were exposed to LED-lights and acquired their first smartphone. After controlling for sleep quality and duration, and several lifestyle and demographic factors, the associations remained significant. Based on the data from this cross-sectional study alone, it is not possible to establish if there is a causal relationship between light exposure and the development of the disorders, whether the light exposure is a consequence of the disorders or whether there is another mediating factor. For example, patients high in anxiety such as PTSD, general anxiety disorder or psychosis may choose to sleep with the lights on, and patients with manic symptoms tend to have lights on when awake at night. However, whether cause or consequence, it is however safe to interpret that many patients reporting psychiatric disorders were exposed to unhealthy light conditions, when they should not. We know that wrong light at wrong time counteracts recovery from psychiatric disorders.  Light exposure interventions are successfully used as treatment for major depression and bipolar disorders. We also know that unhealthy light promotes weight gain, which is a risk factor for the most common cancer types and cardiovascular disorders. These somatic disorders are the main cause of the increased mortality for people with psychiatric disorders, with consistent findings of shockingly 20-25 shorter life expectancy as compared to the general population. Unlike most other known environmental factors affecting health, light conditions can be optimized with low cost and minimal risk. This study is yet another wake-up call that we should talk about light - both in the treatment context of each individual patient and at a societal level.

We've got a new participant, UPRtek. They are pioneers in developing high-quality solutions for light meters, flicker frequency meters, spectrometers, and spectroradiometers. “We hope to join The Good Light Group in promoting the importance of good lighting to the world, as UPRtek's mission aligns with that of The Good Light Group. Here, there are many pioneers in the lighting industry, and we believe that good lighting also requires excellent professional measuring instruments to complement it.” Hedy Lee | Deputy Sales Manager UPRtek More info about UPRtek

16 April, 15:00 - 16:30 CEST ​ The Good Light Group, together with the Society for Light Treatment and Biological Rhythms (SLTBR), the Daylight Academy (DLA), and Luger Research (LR), are organizing and presenting the “deLIGHTed Talks” lectures. The lectures are free to join. ​ Programme ​15.00 Introduction Welcome, Introduction by Charna Dibner, Geneva University ​ 15.10 by Kathryn Reid, Northwestern University ​ 15:30 Diabetes in the daylight: metabolic benefits through natural office lighting? by Jan-Frieder Harmsen, RTWH Aachen University ​ 15:50 Panel discussion Including Q&A with the Audience Panelists: Kathryn Reid & Jan-Frieder Harmse Moderation: Charna Dibner More info

Renske Lok, Ph.D. Stanford University, Department of Psychiatry and Behavioral Sciences Beyond its role in vision, light plays a significant role in shaping our physiology and behavior. Light exposure at night influences alertness, cognitive functioning, and melatonin production. The effects of light on these non-visual functions are contingent upon factors such as intensity, timing, temporal pattern, and spectral properties of light exposure, and there is compelling evidence that these dependencies may vary with age. Photo by Renske Lok Aging and light intensity Numerous studies investigating the non-image-forming effects of light intensities have been conducted in young, healthy adults (18-40 years). However, an increasing number of studies underscore that such effects may not be the same over the lifespan. For example, when investigating how evening light of different intensities (ranging from 5 to 5000 lux) relates to melatonin suppression in preschool-aged children (~3 to 5 years), researchers found that melatonin levels were suppressed across the full range of intensities examined (Hartstein et al., 2022). In contrast, in those aged 18-44, half of the fitted maximal melatonin-suppressing effect of light is estimated to be induced by ∼50 – 130 lux (Cajochen et al., 2000). While there wasn't a clear intensity-dependent response in preschool children, the lowest quartile of light intensities (5–40 lux) showed a notably lower average melatonin suppression than the higher quartiles, indicating that the chosen light intensities might have been too high for this age group. On the other side of the spectrum, older adults (~60 years and up) exhibit a lower sensitivity to light compared to their younger counterparts, suggesting that older individuals may require increased light exposure to attain the same benefits experienced by the younger population (Duffy et al., 2007). Age-related ocular conditions, such as cataracts, lens yellowing, and behavioral changes, contribute to decreased light exposure for older individuals. This population often resides in dimly lit environments and has restricted access to natural daylight, ultimately diminishing circadian light sensitivity by limiting the amount of light reaching the retina. Aging and light spectrum The prevailing consensus is that the circadian system exhibits its highest sensitivity to light at approximately 480 nm in wavelength. This particular wavelength maximally stimulates the melanopsin-sensitive photoreceptor, which plays a predominant role in the non-visual effects of light. While other photoreceptors, such as those sensitive to shorter wavelengths (S-cone) or longer wavelengths (M-cone or L-cone), also contribute to non-image forming effects, their impact is comparatively less significant than that of the melanopsin-sensitive light cells. A recent study proposes that the involvement of other photoreceptors in the non-image-forming effects of light may change over the lifespan (Najjar et al., 2024). In a within-subject design, researchers exposed young and older individuals to narrow-band lights ranging from 420 to 620 nm for 60 minutes at night to assess the effects on melatonin suppression. The study found a straightforward pattern in young adult participants (~25 years): melanopsin solely drove melatonin suppression at all time intervals. The peak sensitivity was identified at 485.3 nm after just 15 minutes of light exposure. However, in the older group (~59 years), the process was jointly driven by melanopsin, the short-wavelength-sensitive (S)-cone and medium-wavelength (M)-cone, with a stable peak sensitivity around 500 nm at 30, 45, and 60 minutes of light exposure. This suggests that as humans age, there's a shift from a reliance on melanopsin alone to a more intricate interplay of photoreceptors in regulating melatonin suppression. Future perspectives Collectively, these studies mark the initial strides toward a nuanced comprehension of the non-image-forming effects of light across diverse life stages. The shift from the reliance on melanopsin in youth to the intricate interplay of photoreceptors in older age, along with the notable impact of low-intensity evening light on children versus higher-intensity lighting in adults, opens doors for tailored approaches to light therapy. It underscores the crucial role of a well-considered lighting environment at every stage of life and emphasizes the significance of careful sample selection in research studies. However, a need remains to unravel how a combination of different light intensity and spectral composition variations influence melatonin suppression and whether these lighting effects extend to other non-image-forming effects, such as mood and cognitive performance. Further exploration in these areas will contribute to a more comprehensive understanding of the intricate, multifaceted relationship between light and well-being across the lifespan. References Cajochen, C., Zeitzer, J.M., Czeisler, C.A., Dijk, D.J., 2000. Dose-response relationship for light intensity and ocular and electroencephalographic correlates of human. Behavioural Brain Research 115, 75–83. Duffy, J.F., Zeitzer, J.M., Czeisler, C.A., 2007. Decreased sensitivity to phase-delaying effects of moderate intensity light in older subjects. Neurobiology of Aging 28, 799–807. Hartstein, L.E., Behn, C.D., Akacem, L.D., Stack, N., Wright Jr, K.P., LeBourgeois, M.K., 2022. High sensitivity of melatonin suppression response to evening light in preschool‐aged children. Journal of pineal research 72 (2), e12780. Najjar, R.P., Prayag, A.S., Gronfier, C., 2024. Melatonin suppression by light involves different retinal photoreceptors in young and older adults. Journal of pineal research 76 (1), e12930.

To determine if you’re living and working in good light, its’ best to spend at least 2 hours outdoors in daylight each day. Daylight is always good for people. However, if you are indoors, how can you ensure you have sufficient light indoors? To determine if indoor lighting is sufficient to improve your health, sleep and happiness,  we need to measure the intensity of light that reaches our eyes. Light levels are typically measured in ‘lux’ which quantifies the amount of light per square meter and thus indicates the intensity of light perceived by our eyes. Lux helps to understand the brightness or dimness of a space. The recommendation is to have indoors at least 500 lux light in your eyes, which is rather easy if you are close to a window. If you are further away of a window you need to compensate the lacl of daylight with electric light to get to 500 lux. Think of it like this: if you're in a room with large windows and plenty of sunlight coming in, it will have a high lux level. But if you're in a dimly lit basement with only a small lamp, it will have a low lux level. Because our eyes adjust to the lux level of a room, they aren’t a reliable measurement tool. That's why we use a mobile app or a lux meter to measure light. Lux is important because it affects visibility and can influence productivity, health and mood. For example, in workplaces, having the right amount of light at the right time can help you work more efficiently and boost your mood. Our recommendation is to aim for at least 500 lux during the day and less than 10 lux during the night.

This Friday March 15th, marks World Sleep Day. The theme of this year is Sleep Equity for Global Health. Good light (daylight or electric light that mimics daylight) is essential for good sleep. If you think you need darkness for better sleep quality, you are completely right. You need darkness at night. But you also need bright light during the day. Daylight is the best! Consider yourself sitting in a dimly lit room during the afternoon for around half an hour. How would you feel? •             A: Bright, active and full of attention •             B: Awake, but not very alert •             C: Sleepy, hard to keep my eyes open Photo by Clint Patterson on Unsplash Did you answer not very alert, or even sleepy? So, this is what a lack of light can do to your brain! With more daytime light you feel active and you sleep better at night. So, if you want to improve your sleep, focus on the right light at the right time. Here are 4 simple rules: 1.           Go outside during daytime as much as possible 2.           Use bright light in the morning 3.           Dim your lights towards dinner 4.           Make the night as dark as possible More info on our try page

We have a new partner! Utilicht, with over 35 years of experience in lighting advisory and plan development for diverse projects and clients – ranging from individuals to hospitality, retail, and large utility projects. Through collaboration with our group, Utilicht can offer innovative and effective lighting solutions tailored to the preferences and requirements of different users while giving the health and well-being of the users also a priority. Utilicht also supports our mission to enhance the quality of life for millions of people worldwide by good light. utilicht.nl

Jan Denneman says, "There's hardly a living creature that willingly stays indoors, with a few exceptions." We're all familiar with the benefits of exercise, a balanced diet, and enough relaxation for good health. But did you know that light plays an equally crucial role? Those who maintain a healthy exposure to good light tend to sleep better, experience reduced stress, more energy and happiness. "The influence of light on our health," Jan Denneman informs you about the effects of light on human well-being and shares practical advice. The masterclass is in Dutch, for the link please see the end of this article. In winter, when daylight hours are shorter, how does this impact us as humans? "At this time of year, we often feel more tired, down, and our circadian rhythms are frequently disrupted. Scientifically proven, people tend to be less happy during the winter compared to summer, simply because you get insufficient daylight." Why is daylight essential for a happier life? "It's how nature operates. Just as a compass aligns with the Earth's magnetic field, humans are designed for daylight. All life on Earth – plants, animals, and even microbes in the sea – relies on daylight. With a few exceptions (like moles), no living creature voluntarily chooses to stay indoors. However, centuries ago, humans started spending more time indoors, which goes against our natural instincts and internal body clocks." How does our biological clock function? "The biological clock, located in our brain, prepares our bodies for upcoming events, such as a good night's sleep. Synchronization with real-time is crucial for a properly functioning biological clock. If you naturally wake at 7 am and sleep at 11 pm, your biological clock is likely in good shape. But, if you consistently wake up tired and rely on an alarm clock, your biological clock may be disrupted. Scientific studies indicate that you can only synchronize your biological clock with light. Apart from rods and cones, which enable vision, our eyes also contain spheres linked to the biological clock and mood regulation. These cells require more light than those responsible for vision. Therefore, I always carry a light meter to ensure I'm exposed to sufficient light to stimulate these cells." How do we know if we're receiving sufficient light, and if these spheres are doing their job? "According to research, during daylight hours (between 7 am and 6 pm), you should receive at least 250 lux of natural light or 400 lux of artificial light through your eyes. Convenient apps like Light Meter for the iPhone can measure illuminance. Outdoors, you'll naturally receive 250 lux or more when the sun is up, but indoors, unless you're near a window, you'll need to adjust lighting. However, in the evening, aim for much lower light levels, ideally less than 10 lux, to prepare your body for sleep." What are some practical tips for increasing daylight exposure during dark days? "Morning light is most effective, so go outside when the sun rises. Even on dark, rainy days, outdoor light is significantly stronger than indoor light and adequate for our eye spheres. Staying indoors? Ensure sufficient artificial lighting. Secondly, opt for a workspace with a window view, as you can benefit from daylight without stepping outside. Also, take regular breaks to gaze out the window for at least 20 seconds every 20 minutes; it relaxes your eyes and provides light exposure. Do you struggle to wake without an alarm clock? Consider using a light-based alarm clock. This allows your body to awaken naturally from deep sleep without being startled of the jarring sound of a traditional alarm." And thirdly, install extra light during the day if you are not able to be close to a window with natural daylight. You should at least get a light intensity of 400 lux in your eyes during the whole day, and less than 10 in the evening. What's the goal of The Good Light Group foundation? "To raise awareness about the impact of light. I believe it should be integrated into every wellness program because it's as important as healthy eating, exercise, and relaxation. Plus, getting enough light requires less effort than hitting the gym, doesn't it? So, go for it!” Original Dutch tekst by: Djaydee Kraus Watch the masterclass (in Dutch)