I recently had the pleasure of interviewing Mariana G. Figueiro, PhD, Professor and Light and Health Program Director, Lighting Research Center, Rensselaer Polytechnic Institute. The topic: what we know, what we don’t know, and what’s currently actionable in design concerning light and health. I’m happy to share her responses with you here. The interview informed an article I wrote for the December issue of ELECTRICAL CONTRACTOR.
DiLouie: The relationship between light and health is now turning into a conversation about best practices related to lighting design and health. How do you feel about where the industry is currently going with this? Do you think we’re getting it right? Where are we getting it wrong?
Figueiro: I think that the industry is in its infancy when it comes to developing products for light and health applications, but at least they are thinking about it and they are now considering this topic in their R&D. My concern is that a lot of the talk is about dynamic lighting systems or blue light. Light and health is much more than these two topics. Correlated color temperature is a factor, but not the only one. Light levels are just as or perhaps even more significant than spectrum alone. Temporal characteristics of light (timing and duration) need to be considered. Timing of exposure is key and depending on whether one is a dayshift or a rotating shift worker, the timing of exposure needed to promote entrainment is different. The same intensity and spectrum of light given in the morning will have a different effect on your sleep time than if it is given in the evening.
Moreover, how much light you get over the course of the day will affect how light will impact your circadian system. The circadian system “sums up” morning and evening light and uses the net result to either advance or delay our biological clock. So, we need to know the characteristics (intensity, spectrum, timing and duration) of our light exposures before we can determine what constitutes healthy lighting for each of us. Also, “morning” for me is different than “morning” for you, so a dynamic lighting system that provides high CCT during the day and low CCT in the evening may be too simplistic, yet, we need to start somewhere and if being simple will help start the process, that works for me.
Our research also shows that red light, which does not affect melatonin production, can increase daytime and nighttime alertness and can affect other hormones, such as cortisol levels. So, it’s not just about blue light.
DiLouie: To summarize as short and sweet as possible, what do we currently know with a fair degree of certainty about the relationship between lighting and health?
Figueiro: 24-hour light-dark patterns reaching the back of our eyes set the timing of our biological clock and exposure to (or lack of) light at the right time or exposure to irregular light-dark patterns for long periods of time can disrupt our biological clock. Disruption of circadian rhythms by irregular light/dark patterns can lead to poor sleep and poor performance, and if experienced over many years, chronically, it can lead to more serious diseases, such as diabetes, obesity and even cancer.
DiLouie: What don’t we know yet? What research is being done to gain this knowledge, and how might it affect lighting practice?
Figueiro: Most of the data we have are from laboratory studies performed under controlled conditions and we have average responses. We do not know much about individual responses and we do not know the exact amount of light needed to affect circadian rhythms outside laboratory conditions. But let me be clear, this does not mean we don’t know enough to start using some of this knowledge in real life applications.
We also don’t know how much light one is exposed to during their waking hours in their own environment. We don’t know whether people will adapt to their light/dark pattern exposures. For example, we measured circadian light exposures in people in Sweden during winter and summer months and we saw a large difference in circadian light exposures, but not much difference in their sleep patterns, though they did report feeling sleepier during the winter days than during the summer days.
DiLouie: What are the “killer apps” for lighting design based on light and health research?
Figueiro: Lighting for older adults, including Alzheimer’s disease patients, is the low hanging fruit. It is ready for prime time, especially in more controlled environments, such as assisted living and nursing homes. This is because they are in a more controlled environment and we can adjust their 24-h light-dark pattern to increase circadian stimulation during the day and reduce it in the evening.
A second close to being a killer app is schools, where we can also control the daytime light exposures. But, for it to be successful, we need to also inform the kids and their parents on what is the best lighting for the evening hours (what to do and what to avoid to do at home).
DiLouie: Do you feel the lighting industry is ready to apply current research to general lighting in commercial buildings beyond these “killer apps”? Is this knowledge actionable for all commercial buildings?
Figueiro: We are ready to start. We talk too much about light at night, but we should also be talking about how little light we are exposed to during the day. Energy codes are bringing light levels in the built environment to levels that are too low for activating the circadian system. So we should be concerned about developing these codes and standards based on visibility only.
Yes, we need to start somewhere, and while I don’t think we can claim we will improve health or performance, we have the potential to impact alertness and reduce sleepiness. Studies have shown that high daytime light levels are associated with an increase in objective alertness, measured using EEG, and a reduction in subjective sleepiness, but not all of the studies show an improvement in performance or better sleep and mood. Light can have an acute alerting effect on people, so, again, it is not just about blue light, acute melatonin suppression and circadian entrainment.
I am comfortable saying that light during the day can increase alertness, but we still don’t know how it can affect health, sleep and performance. Nevertheless, one would argue that high circadian stimulation during the daytime hours and low circadian stimulation in the evening is simply common sense.
DiLouie: What general recommendations would you give to a lighting practitioner hoping to design a lighting system in a commercial building based on current research? How are these recommendations different than current best practice design?
Figueiro: Vertical illuminance is what matters, not horizontal illuminance on the workplane. The addition of windows in the space does not mean one will have greater circadian stimulation. The lighting system cannot be static, but needs to be able to change (light level and maybe spectrum) over the course of the day. Dayshift workers have different needs than nightshift workers, so when designing for a 24-hour facility (e.g., healthcare), the designer needs to account for these differences. Lighting needs to be designed for the individual, not for the building. Task light may be the key. Controls might become essential (manual is fine; they don’t need to be smart controls to avoid extra cost). Short wavelength light matters and it can be good or bad, depending on timing of exposure. Using 6500 K light sources rather than 3500 K may be more common in the future.
DiLouie: What does this look like, exactly? What kinds of sources and equipment would be involved?
Figueiro: We would not be using ceiling lights only; vertical surfaces, such as cubicle walls should be lighted. Task lights that can be controlled by each individual will be more common. Personal lighting systems that can be used to deliver individualized circadian lighting to individuals will be more commonly applied.
DiLouie: There’s only so much the building environment can do to be supportive of circadian regulation during the day. What the user does at home at night is even more important. What general recommendations would you give to the average person?
Figueiro: Correct. It is about the total light exposure during waking hours, so one needs to make sure he/she is not exposed to light levels above 20-30 lux of a warm source starting 2 hours prior to natural bedtimes. Turn off self-luminous displays, or at least dim them down or filter them using orange-tinted filters.
DiLouie: What is the economic benefit here for the lighting system owner? Why should they care if occupants have proper circadian regulation?
Figueiro: People are the most important asset of an organization. Why not provide them with the best lighting pattern we can? Providing occupants with proper circadian lighting is similar to providing them with ergonomic chairs or flat screen computer monitors.
In addition, offices with daylight are more valuable and can be sold or rented for higher value. The same can be established for offices with good circadian lighting.
DiLouie: Would taking walks and lunch outside be enough? What kind of duration is needed?
Figueiro: Taking walks or lunch outside and working near windows can help provide what’s needed in terms of light intensity. 30 min walk in the morning should be enough. Also, perhaps the office spaces should have a light shower (or light oasis) room where people can bring their laptops and work while getting the light they need.
DiLouie: Is there any harm to implementing circadian lighting in a commercial building? How would you answer critics who see circadian lighting as being potential harmful?
Figueiro: We just said that taking walks outside is important. How is implementing circadian lighting in commercial building different than exposing oneself to daylight during the day? The key is to remember to reduce circadian lighting in buildings where people are working at night. It is also important not to make claims about improved health, well-being, and performance. We have not quantified the benefits of circadian lighting on people outside laboratory conditions. We can only state the benefits based on laboratory conditions, but the science is clear: light is the major regulator of circadian rhythms to the local time on earth. But, it is important to remember that one can be perfectly entrained, but have a social life that will preclude him/her to sleep as long as they should. So, as my grandfather used to say, you can bring the horse to the fountain (add circadian lighting to the buildings), but you cannot force it to drink (one can disrupt himself/herself with other activities and lighting will not be enough to maintain entrainment).
DiLouie: If everybody adopted LRC recommendations for circadian lighting, what would be the benefits?
Figueiro: While we cannot state that everyone will sleep better, we think that a good portion of the population would be more entrained and therefore sleep better. Better sleep is associated with better performance and better health. Moreover, if anything, we will not have dingy, dark environments.
DiLouie: If you could tell the entire electrical industry just one thing about lighting and health, what would it be?
Figueiro: Don’t be afraid to try. It may not help everyone, but if it helps only half of the people occupying the building, it is worth it.
DiLouie: Is there anything else you’d like to add about this topic?
Figueiro: It seems to me that we know, for sure, that a regular 24-hour light-dark pattern minimizes disruption, which in turn minimizes negative health and performance outcomes. Where we get into trouble is jet airplanes, self-luminous displays, dim interiors, staying up late to watch hockey, and moving from building to building and space to space throughout the day. The 24-hour light-dark pattern is no longer regular and predictable.
The challenge for the traditional lighting and electrical industries is that they have been so closely tied to thinking about a particular building – that’s where one needs to see tasks and perceive ambience instantaneous. Circadian hygiene is not instantaneous, but cumulative. Today, because we have luminous displays and active lives that change our 24-hour pattern of light dark, we do not have a single industry that is responsible for the full 24-hour light exposures patterns, and therefore cannot address the 24-hour light exposure issues.
A new profession needs to emerge, like a personal light and health coach, or a new software app that keeps track of light-dark exposures an provides recipes for maintaining or correcting circadian disruption. We’re not there yet except where people don’t change their living space across the 24-hour day (e.g., senior houses and submarines). The further we get from predictable light exposures, the more likely we are to cause harm.
One area for real impact could be school kids – they have a regular routine at school and with education of parents, light could be better controlled to ensure adequate and consistent sleep. So, now, fix the senior living facilities and next educate teachers and parents about the significance of a robust 24-hour light-dark pattern. Offices are going to be hard, but something like “a light oasis”, where workers can get their circadian light exposures during the daytime (granted that they need to know what they need, and for that, they will likely need a circadian app). Airline pilots, flight attendants and shift workers, nearly impossible.
