Potential exists for SSL to positively impact health and wellbeing, but science lags

MAURY WRIGHT interviews Finelite CEO TERRY CLARK, and the early advocate of LED lighting shares his investigation into the area of human-centric lighting and where science falls short of supporting theories of benefits for now.

LEDs Magazine has published numerous articles over the past several years that would indicate that lighting with a specific spectral power distribution (SPD) could yield tangible benefits to human health and wellbeing. For example, blue energy in light is said to increase alertness and productivity in the morning. Warmer light is thought to prepare us for a restful night. The claimed benefits have ranged from simply better rest to accelerated healing and more productive work forces. Often called human-centric lighting (HCL), the application is particularly symbiotic with LED-based lighting because of the ease with which LEDs can be used to produce specific SPDs, even in fixtures that can be tuned dynamically based on the time of day, or other criteria. But does science support the HCL claims?

Recently, there have been questions raised about the scientific evidence of real health benefits attributable to lighting. Indeed, a panel of top researchers from leading organizations around the globe authored an article in the academic Trends in Neurosciences publication entitled "Measuring and using light in the melanopsin age" (http://bit.ly/1opWQDW) The article discuss the non-visual photoreceptive cells that might be the key to health benefits from light exposures. But the paper points out more questions that need to be answered rather than answering questions about HCL. Indeed, the paper led the US Department of Energy (DOE) to publish the fact sheet "Lighting for health: LEDs in the new age of illumination" (http://1.usa.gov/XANXwf) The DOE concludes that for now LEDs should not be considered more beneficial or harmful than conventional sources but cautioned the industry on health claims.

The recent escalation in discussion on HCL led us to seek more input on the topic. Terry Clark, CEO of early LED lighting player Finelite, has both a personal and professional interest on the topic of HCL. Clark is a pioneer in LED lighting and a regular speaker at industry conferences. He has been researching HCL so we asked for his insight on the topic and the recent research.

LEDs Magazine: Let's start at perhaps where we should finish. Can lighting positively impact our health and wellbeing? Based on the recent research, I know there are many issues that need further scientific study. But are you of the opinion at least that lighting can positively impact health and wellbeing?

LEDs Magazine: So the touching your soul is nice to have. What we're starting to talk about is a healing thing or a tangible benefit to our wellbeing. We have published, and even more so companies have published, research on the benefits of the right spectrum to increase student productivity, accelerate healing in hospitals, eliminate jet lag on overnight international flights, and similar scenarios. Is any of that research valid?

Clark: Regarding that question and certainly companies that have published research on the benefits of the right spectrum increasing student productivity, I have never seen a properly vetted article that says the color temperature or spectrum of light improves student test scores over any measurable period. The only one that's ever been done in the US was one international firm did one study of one school I believe in the South, in Kentucky maybe; and we asked the school coordinator did he think the results were expandable to other districts, to other schools, and he said absolutely not. There were no controls; there were no long-term studies; there was no control of any of the outside variables. They measured preference. The teacher said, "Hey, I like this." But there was no documentation. Consider even Finelite's work. I've got 80 million data points that can't tie spectrum to better test scores.

LEDs Magazine: We have also seen a Philips school study in Germany and studies from medical facilities in Europe that would indicate faster healing attributable to light spectrum.

Clark: It is not a well-vetted study. The one in Europe really doesn't look at the students long enough. And the teaching moment comes from the number one industrial engineer in the old AT&T Electric and what is called the Hawthorne Study. People made a change in lighting and the productivity on the line went up, and AT&T got really excited - "Ah, we have found the Holy Grail." And they went in and took out the temporary lighting and productivity went up again. What they found they were measuring was the employees loved the attention. They loved the fact that they were being recognized and they were being treated and groomed over. It wasn't the different light temperature at all. So if there is a tie of spectrum and student productivity, absolutely I've never seen it. The tie between spectrum and accelerated healing in a hospital I have not seen properly vetted by any healthcare facility and I will come back to that. I haven't seen that study.

LEDs Magazine: We did cover research from Philips on the Maastricht University Medical Center that revealed patients healing better when exposed to tunable lighting relative to patients under legacy lighting. The benefits were primarily attributed to patients sleeping better because the lighting matched their circadian rhythm. Likewise, there was a study that indicated international airline passengers rested better and were more productive after a long flight based on tunable lighting.

Clark: And that goes to the third point, if there is any jet lag and certainly there are articles that proper lighting is a major factor in assisting in dealing with jet lag. And that's the light and circadian rhythm tie with the intrinsically photosensitive retinal ganglion cells (ipRGCs) covered in the neuroscience research. We know there is a direct tie between lighting and any number of chemical regulators that come out of your brain, the hormonal secretions. And yeah, so there is a tie. But the benefits of the right spectrum again have not been fully vetted.

Then your question is, does the research described in that complex article on the melanopsin age negate all these things or support them? I sort of see them differently. The article to me explains why it is so incredibly challenging, and we as an industry - if we care about this - have to link in literally with brain researchers. The reason why is when you take those ipRGCs cells they have very, very complex interconnections with your rods, with your cones, and with their own sensing, so they are actually reading five different wavelengths of light at the same time. Page 2 of that article has a diagram, and the rods keep responses at 507 nm. People respond to light both above and below that wavelength - your color is 535 nm, your melanopsin is at 480 nm, and the other colors are at 565 nm. You are getting a dose into those various sensor elements kind of, though, to your point, the whole spectrum. You have an extraordinary, complex relationship that would take the exact intensity over that whole expression versus the receptivity of the rod. And then we are trying to figure out how it integrates because the article says the cell is one millionth as sensitive as your rods and cones. So to get one photon into that little cell, you need a million hitting rods and cones.

It's kind of like the brain is cheated. It knows it's got a sensitivity, but it's not very good so it's literally stealing information from the rods and cones. So some of the circadian rhythm, they have found, if you just put enough red light intensity into that red rod you can trigger the circadian rhythm - to wake it up with a red light. Because you actually fire that red spot, which ties into the ipRGC cell; and it says "OK, so whatever it is, maybe it's a fire, maybe it's something but wake up, we've never seen this much red in our life!" and the hormones start screaming through the brain.

So when it comes to things like jet lag, is it the 480-nm light required or what mix can I do it with - just blue and 535 nm? And that's where the dosing thing comes in. So you need a one-millionth time dose of 480 nm that's pipelined in; and the one coming in at 420 nm, the deep blue, that's got chokes and throttles on it where it gets in. What the article is saying is that the dose is really important and it's a tough mathematical thing, especially when the sensitivity of that blue drops off so fast.

So you can do it; the math will get done in some creative time. You know, just look at what Google's done with self-driving cars. But the math has not been done yet. And why it's going to take brain researchers is the next thing the article says - Oh, and by the way, it really depends on your state coming into the light exposure. Were you tired? Were you jet lagged? Did you have too much alcohol? What other states come into play?

There was a Light + Behavior conference presented by the IES in Cleveland. They had - for the first time I've seen in a real public event - three distinctly lit areas. One had an incandescent A-lamp. The second was a magenta-saturated room and the next room was deep saturated in blue. You walked into it and you looked at the incandescent light, and it was just like you'd expect any 2700K lamp to look like, beautiful warm yellow light. And then they escort you into the magenta room and they talk to you for two to three minutes. Then you go back and look at the incandescent and it is green. You would swear you are in Wizard of Oz. They claimed that your brain is desperately trying to get back to the black-body curve and literally changes your color perception on that magenta, and therefore normal white light looks green. When you went into the blue room, you see it completely differently again.

That's an example of what's happening in the canonical visual cortex. They say what is going on in the chemical engine is somewhat similar. Where you come from completely impacts how the brain is going to get that signal out of the nerves. So I've got five different inputs. I've got the early state I'm coming from that is very important, and there's why they say to be careful, just really, really be careful.

LEDs Magazine: Does that imply that you as a company, Finelite, would not offer a product today that was promoted as being human-centric or that was promoted as maybe having a spectrum where you should use this setting for late night, this setting for early morning? Would you offer such luminaires for maybe hospital applications?

Clark: We are very actively participating in the area of light color tuning. However, our approach will be very carefully stated that we will be working more in the area of preference rather than trying to claim health. There is very strong evidence that certain people prefer warmer or cooler colors, and it is pretty well documented that sometimes people get into a change of interior colors in their space; if they had the ability to shift the color spectrum one way or another they would find the space definitely more appealing under one set of color. So giving users control, I think, is the first step and you will see Finelite promoting that.

And you will probably see Finelite undertake some research in certain specific areas to say okay, if you give people control like that: One, do they use it, because it's one thing to give them control but you've got to have a vetted study; do they use it? Two, do they use it to set their own preferred level and then leave it there forever, or do they change it during the day or do they change it seasonally? To do that you need to take data readings almost every minute of the day for at least a calendar year to get the data set.

And I'll tell you we've done that in education and you get real quickly 80 million data points. And all that says is preference. Maybe it doesn't even say preference. It just says do they use it, and if so, how frequently do they use it?

LEDs Magazine: And then in the applications it might be different. For example, an office environment would be different from a medical environment or even retail.

Clark: I think where we might expect to see it used, for example, is in very high-end executive meetings where you have lots of international customers or very high-end hospitality where anecdotally certain people like warm colors and want it down to the 2700K area, then others anecdotally like the cooler temperatures. So wouldn't it be great if you were having a meeting with very important guests and you could ask them not only would they like to adjust the intensity level so that it is most pleasant for them but also color. That can add significantly to the comfort of my important guests or visitors or executives.

LEDs Magazine: When you talk about something like that executive conference room, and you approach it from saying this is really a preference thing, but that doesn't prevent somebody from saying, "Well, if I move this toward the cool end of the spectrum, it may help me with my jet lag." The preference thing is clear and the true jet lag benefits are kind of loosely supported at this point.

Clark: That's right. If they do come up with a good integrating meter as the melanopsin article sort of pleaded, you could put it in the room. And if we are building luminaires that can adjust intensity and spectrum the research ultimately says, "Hey, if you're at this intensity and this color spectrum then that will help jet lag." Then we will have built a very affordable, easy-to-use system where somebody could punch in the CCT and adjust the intensity level and say, "If you just sit in this for 10 minutes, you'll feel better." But we won't claim it. We will not claim that we can characterize every one of those five spectrums and exactly how the ipRGC cells are going to work.

I don't know if you saw the area in that article that said oh, by the way… The doctors or brain researchers have already found there are at least five types of ipRGCs so the brain chemical isn't driven by warm; there are five separate chemical paths. We don't even know if jet lag is controlled by two of the five, or one of the five, or if all five have to fire. So this is why I take a deep breath and why I'm also absolutely so energized. This is the best industry in the world to be in, and my God, brain researchers are working on the brain thing and when we figure it out we're going to get smart. But we got to take that deep dive and understand it's going to be complex before we can claim we're smart.

LEDs Magazine: Regarding the brain researchers, when we talked previously you made the point that yeah, we need to be involved with them, but we don't want them to take over our lighting world. But it does have to be a partnership at some point, right?

Clark: I think so. I think they need our expertise on how to move the photons around and we need their expertise on how the brain works and so that's two parts of the brain. A lot of brain researchers that we were talking to in light and behavior are dealing with the visual cortex part of the brain. A lot of the people in HCL are saying, "I want to deal with the chemical part" and they literally ignore the conscious part of the brain, which is very important on color preference, color fidelity, and the flicker is impacting the cognitive part of the brain.

LEDs Magazine: Two years ago the LRC presented their study on white preference at Strategies in Light that revealed most preferred white located below the black-body curve. At LightFair we saw Philips with their CrispWhite LED below the black-body curve and also with some deep blue energy to excite the brightening agents. Luminus Devices had a similar type of LED. But what I think you said to me at LightFair was that such preference tests may not be valid research because it depends on what the test subject was looking at before, or as we discussed earlier, the test subject's state before the exposure.

Clark: Yeah, and that's the thing they were teaching at the Light + Behavior event that I mentioned. The perception of the white glare, how your brain perceives that color is absolutely dependent on the color it just came from. There is very good research that documents how people like white relative to the black-body curve. It is an excellent piece but it takes so long per student. It's something like four hours to go through the preference testing because you've got to adapt, and then once you're adapted you are asked, "Do you like this color or that color better?" and then you've got to re-adapt and ask, "Do you like this color or that color better?" The room required for testing is like $50,000. We desperately need that rerun again and there just isn't budget to do it. We didn't deal with age and we didn't deal with the cultural elements. Were there more Asians in that study or more Europeans? The researchers were amazed to find the results but have never been able to deep-dive back into it.

EXTRA! Read the full version of this interview at ledsmagazine.com.