Principles of Healthy Lighting

Highlights of TC 6-11 Report

Ottawa Lighting Mini-conference

JAV 07-Oct-2002

National Research Council Canada

Conseil national de recherches Canada

Principles of Healthy Lighting: Highlights of CIE TC 6-11's Forthcoming Report Jennifer A. Veitch, Ph.D. Institute for Research in Construction Canada

This talk is derived from a forthcoming CIE committee report on “Ocular Lighting Effects on Human Physiology, Mood, and Behaviour" (TC 6-11), a committee I chair. I'm indebted to my colleagues on the committee for much of what I am about to say.

Dr. Jennifer A. Veitch

1



JAV 07-Oct-2002

Outline p p p p p

Introduction Principles of healthy lighting Architectural applications Measurement issues Conclusion

The report itself has many other sections; this talk is only 30 minutes, so I’ve chosen to focus on the conclusions.


2



JAV 07-Oct-2002

Lighting Quality

As you know, the old emphasis on lighting for visibility alone has given way to a more comprehensive model of lighting quality, in which lighting must meet many human needs while being integrated with the architecture and respectful of the environment and the economic conditions. Lighting for good health is part of this definition.


3



JAV 07-Oct-2002

Background p

p

p

p

Different retinal receptors process visual and non-visual information One path takes visual information to the visual cortex Another takes information to the hypothalamus Hypothalamus controls many endocrine, metabolic, and higher functions

The background to the creation of TC 6-11 was the recognition of the growing body of scientific knowledge about how light influences human biology, behaviour, and health. Among these findings are evidence that there are two separate functional pathways that carry information about light to higher centres in the brain. The non-visual pathway leads to the hypothalamus, a brain centre that is the coordinator of many functions, including the release of many hormones. Melatonin is among the bestknown of these; it is the chemical signal that regulates circadian rhythms and keeps them in synch with environmental light. Melatonin is secreted in darkness, and suppressed by bright light.


4



JAV 07-Oct-2002

Eye-to-brain Pathways

3

6

5

melatonin secretion

8

4 2

7

1

visual pathway photobiological pathway

1.retina 2.optic nerve 3.visual cortex 4.retinohypothalamic tract (RHT) 5.suprachiasmatic nucleus (SCN) 6.pineal gland (melatonin secretion) 7.spinal cord 8.superior cervical ganglion (sympathetic nervous system)

© Philips Lighting, ALC

This is a schematic of what we know today, although a lot more detail is known. (This slide was given to me by Gerrit van den Beld of Philips Lighting.)


5



JAV 07-Oct-2002

TC 6-11 Report p p

p

Summarizes literature to December 2001 Establishes first set of principles for healthy lighting based on scientific findings First steps towards potential architectural applications

The full committee report summarizes the scientific literature, the cut-off date being last December. This area is rapidly developing and only by establishing a date were we able to achieve a final version. Our goal was, beyond merely providing a summary document, to establish the first principles of healthy lighting and to map out some tentative first steps towards architectural applications arising from these. You will find them very sketchy, as befits an area that is still in its infancy.


6



JAV 07-Oct-2002

First Principle The daily light dose received by people in Western countries might be too low. p Low daily light exposure associated with lower mood p Spending 90% of time indoors might be too much biological darkness, with potentially grave health effects p Necessary dose as yet unknown

Although I would not say that this principle is absolutely confirmed, there is mounting evidence that we in the West do not get enough exposure to very bright light, even if we live in temperate or tropical latitudes where weather and day length are never barriers. This low light exposure seems to be associated with lower mood and feelings of well-being. Because other physiological systems, including immune responses, are also affected by light and by the state of circadian rhythm entrainment, there is potential for more serious health effects.


7



JAV 07-Oct-2002

Mood and Well-being Partonen, T., Leppämäki, S., Hurme, J., & Lönnqvist, J. (1998). Randomised trial of physical exercise alone or combined with bright light on mood and health-related quality of life. Psychological Medicine, Medicine, 28 28,, 1359-1364.

p

Effect of exercise and light on mood and quality of life • Exercise groups got more fit than relaxation • Bright-light group showed bigger mood and mental health score improvement than the moderate-light group

This is one example of the literature that underlies the first principle; by no means is it the only study that led us to this conclusion. This is a well-designed and carefully-conducted field experiment undertaken in Helsinki. The experimental report (which was published in a top-notch journal) details the independent and dependent variables, experimental design and statistical tests in detail. Participants were randomly assigned to one of three conditions, for 8 weeks. They took the treatment for three 1-hour sessions each week. There were physiological and psychological measurements taken at the start, after 8 weeks, and then 16 weeks after the end. The three levels of the independent variable were: dim-light relaxation training – no illuminance value given moderate-light fitness training 400-600 lx bright light fitness training 2500-4000 lx What did they find? Participants who worked out all got fit, but the ones in the gym with bright light also showed improvements in standardised mood and mental health measurements, over the 8 weeks of training. However, 4 months later in follow-up the people who had received the bright light showed the biggest declines: the effect seems to rely on continued exposure.


8



JAV 07-Oct-2002

Second Principle Healthy light is inextricably linked to healthy darkness. p Circadian rhythms are maintained by the pattern of light and dark exposure; we need both p Light exposure at night (while sleeping) might disrupt melatonin rhythms p Necessary daily dark dose unknown

Although we might need more light exposure, we should not forget that circadian rhythms are cycles; they need both light and dark for the rhythm to be maintained. Among the more frightening possibilities is the evidence that breast and skin cancers might be linked to light exposure at night. This comes from three lines of investigation: -in vitro experiments, in which melatonin suppressed the growth of tumour cells grown in a Petri dish; -in vivo experiments, in which mice that had implanted tumours had more tumour growth when they were exposed to low-level light at night, than when they were in total darkness (the hypothesis being that the low level of light partly suppressed melatonin secretion) -Epidemiological, retrospective studies of women with breast cancer (there are three in the literature right now that I know of), which have found that women who were exposed to light at night (e.g., because they worked shifts) had a higher risk of developing breast cancer. Here the hypothesis is that even if they spend the other part of the day in darkness, this might have sufficiently disrupted their melatonin rhythms to cause problems. Dark time also is important to maintaining sleep quality. Disrupted sleep in itself is linked to poorer health and well-being.


9



JAV 07-Oct-2002

Melatonin and Health p

p

p

Urban life has almost constant day length, and high night-time light exposure Without electric light, day length varies seasonally and there is little light after dusk Could modern life disrupt rhythms?

Wehr, T. A. (1997). Melatonin and seasonal rhythms. Journal of Biological Rhythms, 12(6), 12(6), 518-527.

Some scientists think that urban environments offer biological darkness by day (in interiors with relatively low illuminances) and unnatural brightness by night (electric lighting extending apparent day length), producing apparently constant day length over the seasons, and having unknown health consequences. If true, many people have disrupted daily and seasonal rhythms that could influence health.


10



JAV 07-Oct-2002

Third Principle Light for biological action should be rich in the regions of the spectrum to which the nonvisual system is most sensitive. p Exact spectrum unknown, but it peaks in the blue-green region p Necessary daily exposure to these wavelengths not yet established p Potential for energy-efficient delivery of healthy light if source spectrum well-chosen

One very active body of research concerns the search for the melatonin action spectrum. There are three currently in the literature, each slightly different from the others, but all peaking in the range of 455-465 nm (blue-green). It appears fairly likely that the photoreceptor for this process is neither a rod or a cone, but some other type of photoreceptive cell (although there are those that think it could be an S-cone). At present, all we can say is that if we want to use this area of knowledge it will make good sense to develop and use light sources that are rich in this region; however, we are a long way from knowing exactly how much of this light is needed to maintain good health. There are many reasons why we should want to know what the action spectrum is, one of which is the possibility of achieving healthy light without requiring excessively high illuminances everywhere.


11



JAV 07-Oct-2002

Fourth Principle The important consideration in determining light dose is the light received at the eye, both directly from the light source and reflected off surrounding surfaces. p Horizontal illuminance is not the important measurement

This principle is one that will directly influence how we use lighting design to support health. Bathing everyone in very high-intensity blue-green light is NOT what this committee is recommending. Once we know the necessary daily light dose, we need to find out the best ways to deliver it to the eye, not to the desk. Remember, this is not about visibility – it’s more akin to getting your vitamins. There are practical and measurement implications of this too, which I’ll get to later.


12



JAV 07-Oct-2002

Fifth Principle The timing of light exposure influences the effects of the dose. p Nervous system varies in sensitivity over the course of the day p Light effects at night differ from those in the daytime, and recommendations should reflect this

There are three important characteristics of light for biological action: intensity, spectrum, and timing. The effect of a light stimulus depends on the state of the system. Thus, bright light at night, before the low point in core body temperature, has the effect of delaying the circadian rhythm (the low point will come later than it would have). Bright light in the morning, after the low point of core body temperature, will advance the rhythm (the low point will come earlier on the following night than it would have). The same light exposure in the middle of the day might have very littler effect at all. Our recommendations for healthy light need to be precise about the timing as well as the intensity and spectrum.


13



JAV 07-Oct-2002

Architectural Applications p

Lighting Quality Principles • Colours and reflectances of room surfaces are part of the lighting system • Bright vertical room surfaces are generally preferred over dark ones • Control glare

• Controlled used of daylighting • Limit glare and solar heat gain

Those are the principles that our report articulates. I’m now going to discuss what little we know right now about how these principles might influence architectural applications. First, let me say that we are doing this firmly in the spirit of achieving good lighting quality. Our principles for healthy lighting should also respect other lighting quality principles. We neither want to reduce visibility or comfort with glare, nor to cause excess energy use.


14



JAV 07-Oct-2002

Daytime Applications p p p

Put the light where the eye is Control glare (don't create new problems) Provide local control - more light isn't always needed or wanted

One conundrum is how to provide more biologically-effective light without blowing the energy budget or creating glare. According to some recent work we can achieve biological effects with lower illuminances, provided we make sure people really get the dosage. Trouble is, how do you get people to use a head rest or a fixed gaze? The answer is to put light where people will see it – highlighting important things they have to look at, for example. In the Finnish study I described, the researchers gave people higher doses of light using 3 1-hr visits a week to a specially lit gym. Perhaps we don't need more light all the time, but just some of the time - and perhaps not everywhere. This would be a good thing in terms of energy consumption, because to increase illuminance everywhere is unsupportable. The carbon dioxide emissions alone would be prohibitive! As our knowledge expands, this will mean more work for designers to make sure that we get good value for installations: Dark surfaces will negate the benefits of providing additional luminaires, and are likely to result in an unsatisfactory luminous environment in which there is little indirect or reflected light. Bright room surfaces are generally preferred over dark ones, provided that glare is controlled . The room surfaces are, in effect, part of the lighting system. We also argue that local control is needed; biologically-active light might conflict with other needs, or the space might be unoccupied. Turn the lights off or down when necessary.


15



JAV 07-Oct-2002

Daytime Applications p

Daylighting in buildings • • • •

well-being light dose spectrum view

Controlled used of daylighting, limiting glare and solar heat gain to avoid compromising comfort, is an energy-efficient strategy for providing more light where it is wanted and, perhaps, needed - although, of course, it is not a light source available for night shift lighting. It could meet the requirements for intensity and spectrum, although it’s not clear yet if the times of day when daylight is most available are also times of day when the light dose is best use. There's evidence that having a view is in itself beneficial, that it provides opportunities for restorative experiences that relieve people from the demands of work or home.


16



JAV 07-Oct-2002

Daytime Applications

p

Combination task/ambient systems: • might avoid need for excessive general illuminances • could prevent some design problems

This is another possible approach, making sure we don't put too much light everywhere. These systems are of course also a way to achieve good energy efficiency (the photo shows a system at 0.77 W/sq. ft including task lighting). Again, however, we don’t know enough about the necessary light dose to state confidently that any of the bright areas in this scene are bright enough, or likely to be viewed long enough to deliver the necessary dose.


17



JAV 07-Oct-2002

Night Work Applications p

p

p

High illuminances delivered architecturally can influence melatonin secretion and aid in circadian phase-shifting Shift work applications need to be tailored to the specific schedule Examples: luminous ceilings; simulated skylights

One setting where the potential application is clear is night shift work. Bright light exposure during the night shift can have immediate, acute effects on complex task performance and can aid in successful circadian phase-shifting . The bright light might not be needed constantly throughout the shift, but with additional luminaires and appropriate switching (elaborate automated controls are available but would not be necessary to the purpose), biologically effective lighting could be provided to those who must work overnight. This will not solve all the problems of a shift worker, but properly designed bright light exposure schedules can help. The health and economic consequences of better adjustment are profound, for individuals and for society. Luminous ceilings that deliver high illuminance, or simulated skylight apparatus that mimics the evening are both devices that have been tested for this purpose.


18



JAV 07-Oct-2002

Exterior Lighting p

p

Light spill into bedrooms makes light avoidance at night more difficult How bright does a streetlight need to be?

The suggestion from those who think that we live in a perpetual twilight is that nighttime lighting in urban centres is problematic because it maintains that constant low level of light stimulation. At the very least this could be another reason to advocate for exterior lighting systems that do not spill into buildings, especially bedrooms. Perhaps we also should think about our practices for street and exterior lighting, and not only because of concerns about light pollution for astronomers, or energy and cost considerations for municipalities.


19



JAV 07-Oct-2002

Healthy Light Habits p

Day-shift workers: • Daily outdoor exposure & exercise • Light avoidance for at least part of the night (while sleeping) • Sleep hygiene

p

Night-shift workers: • Avoid light exposure during daytime • Maintain fixed sleep time

Both daytime and night-time applications will be more successful if we all adopt healthy habits. For daytime exposure, we could shift away from a purely technical solutions, making people go outside and walk around as a way to get light exposure and the benefits of exercise. One SAD therapy study found that a daily walk outside, even in a cloudy Vienna winter, was an effective treatment. Perhaps your grade-school teacher was right when she said “Go outside and play!“ Our own bedrooms could be places where we actively avoid light at night, while sleeping. This should also cause some reconsideration of night lighting policies in institutions, such as hospitals, so that those who need darkness can get it. For night-shift workers, the benefits of bright light exposure demand cooperation. They must avoid light exposure during the day (wearing dark glasses, sleeping in a darkened room), and as far as possible need to keep to a constant routine. Fastrotating shifts leave people in a constant state of maladapted circadian rhythms. For both groups, teaching people what their lighting needs are will also be important. Right now people don’t self-select the higher light doses that appear to be good for them; just installing more light isn’t likely to solve any problems unless people know how to get the dose they need (this is particularly true if there are individual local controls, which could allow people to get a lower dose than the designer intended or expected).


20



JAV 07-Oct-2002

Measurement Issues p

p

p p

Photometric measurements (V ? and V'?) are based on visual sensitivity What if nonvisual effects use a different receptor? Specify source, use radiometry Develop new sensitivity curve?

Both studying and applying information in this area forces some consideration of measurement issues. Using the usual photopic or scotopic measuring devices builds in the assumption that the process you are studying relies on the normal visual system. These processes don't appear to rely on vision, so using illuminance or luminance is probably not correct. Researchers need to describe the spectral properties of their light sources and the total irradiance. It's a matter of some debate in the lighting community whether or not we need a new spectral sensitivity curve (even V-lambda is thought by some to be error-ful); the more so for this putative new photoreceptor. It will be a long while before any new measurement systems come into common agreement. However, that shouldn't stop us from using more appropriate measurements and more detailed specifications of what lighting conditions people will receive. The lighting community should adopt the analogy of the acoustics community, where reporting several different weighted values of a measurement, and an unweighted one, is common.


21



JAV 07-Oct-2002

Measurement Issues p p p

Light exposure Light dose Design criteria?

Similarly, to know the light dosage received by a person means thinking differently about measurement. Light exposure means the light that is potentially received; but the dose depends on the viewer, too. Instead of reporting illuminance on a surface, we need to think about how much light actually reaches the back of the eye, taking into account : the age and visual state of each subject; the adaptation (background) luminance when the stimulus is given; pupil diameter during the stimulus where feasible, use of head restraints and gaze instructions (so that they look where you want them to, and get the dose you intend); and, measurement at the eye, in the direction of gaze, of spectral irradiance. If it becomes desirable to change the light dose people receive indoors, then we will need to think differently at least some of the time about how we design: where we put the light, and for how long. If we need higher dosages, we probably don't need them all the time - and we can't afford the energy for it either - so we need to get smarter about where and when light is very intense, so we get the effects we seek. Our design criteria will need to reflect this additional set of requirements.


22



JAV 07-Oct-2002

Conclusion

I’m not alone in suspecting that a revolution in lighting recommendations will come in the next 10-15 years, as we expand from purely visually-based recommendations to new ways of thinking about lighting from several angles. The research I've outlined here could have profound effects on interior and exterior lighting, both: so that we get light exposure and periods of darkness, too.


23



JAV 07-Oct-2002

Acknowledgements My thanks to my colleagues & friends: • Gerrit van den Beld (CIE TC 6-11) • George C. Brainard, Ph.D. (CIE TC 6-11) • Joan Roberts, Ph.D. (CIE TC 6-11) p

p

Report expected Spring 2003 - check http://members.eunet.at/cie This paper will be presented at the 5 th LRO Symposium: Light & Human Health, Nov. 3-5, 2002, Orlando, FL

This is not my presentation alone, by any means. These are my fellow committee members. A report on this topic will be available in early 2003 from National Committees of the CIE. You can find out about its availability on the CIE WWW site. This is a version of a presentation that I will give on the committee’s behalf at the LRO Symposium: Light and Human Health, a month from now. You have the privilege of getting the advance notice.


24