Room to Think
Room to Think explores how the spaces we live and work in shape how we think, feel, and function.
Hosted by Lyssia Katan, Head of Brand at LiLi Tile, the podcast features conversations with world-class architects, designers, neuroscientists, psychologists, and cultural thinkers. Together, they unpack how light, layout, materials, sound, and spatial decisions influence stress, focus, creativity, and wellbeing, and share practical insights you can apply in your own home or workspace.
New episodes drop on Tuesdays. Follow Room to Think on Spotify, Apple Podcasts, YouTube, or wherever you get your podcasts.
Room to Think
Light Is a Drug
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In the first episode of season two, Lyssia sits down with Dr. Mariana Figueiro, director of the Light and Health Research Center at Mount Sinai and one of the leading researchers in light and human health, to explore how light shapes far more than what we see. Originally trained as an architect, Dr. Figueiro has spent her career studying how light affects our circadian rhythms, sleep, mood, alertness, and long-term health, and her work asks a simple, overlooked question: what if the light in your home is quietly working against you?
The conversation centers on why Dr. Figueiro describes light almost like a drug. Like medication, she explains, light needs a dose, a timing, and a regularity to work in your favor, and getting the timing wrong can disrupt sleep just as easily as the right timing improves it. They break down what that means in practice: how much light the eye actually needs, why the first hour after waking matters most, and why dimming the hours before bed matters nearly as much as brightening the ones after.
Dr. Figueiro also shares what years of applied research have shown, from redesigning lighting aboard US Navy submarines to help sailors sleep and stay alert on shift, to her long-running work in nursing homes, where increasing daytime light improved mood, reduced agitation, and lowered fall rates in patients with Alzheimer's disease. The conversation also pushes back on a few popular assumptions: why blue light glasses and screen filters are often oversold, why a dim room can look bright enough to fool your eyes while doing nothing for your body clock, and why red light seems to work more like a cup of coffee than a sleep aid.
By the end of this episode, you may realize that better sleep has less to do with what you do right before bed and more to do with the light you let in hours before you even think about it.
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Dr. Mariana Figueiro
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Light and Health Research Center at Mount Sinai: https://icahn.mssm.edu/research/light-health
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Why We Ignore Lighting
Dr. Mariana FigueiroWe do take lighting for granted. You don't really think about lighting. If you flip the switch on, you see, you flip it off, you don't see, and that's about it. What do you mean by that? We need to start thinking about lighting as more than just vision and start thinking about lighting as an instrument for help. You can, depending on when you get that light, you can actually improve your sleep. But if you get that light at the wrong time, it can actually disrupt your sleep and disrupt your circadian system.
Lyssia KatanYou worked with the US Navy on submarines. What was that like?
Dr. Mariana FigueiroWe did very interesting work with them where we changed the lighting in the suburbs.
Season Two And The Big Question
Lyssia KatanIf you have one thing to change, change the Season two of Room to Think is officially here. After 30 conversations in season one, I realized we had barely even scratched the surface. This season brings a whole new lineup of incredible guests, fresh ideas, and surprising conversations about the spaces we live in and the way they shape how we think, feel, and live. We're talking psychology, light, sound, health, behavior, creativity, astrology, and so much more. There are some incredible conversations coming, and I cannot wait for you to hear them. Room to think is back. Season two starts now. What if the way you light your home is quietly affecting how well you sleep at night? Welcome to season two of Room to Think. Today I'm sitting down with the one and only Dr. Mariana Figueroa. She's one of the leading researchers in light and human health, and she really tells us why light does so much more than help us see. It can affect our secretion rhythms, our mood, our alertness, and even the way our bodies function. We get into why Dr. Figuero describes light almost like a drug and what her research with Alzheimer's patients and even US Navy submarines has taught her. We talk about why we may be worrying too much about blue light and not enough about our dark days and the surprisingly simple changes we can make at home to support better sleep and better health. Let's get into it.
Light As A Health Tool
Lyssia KatanHello, Dr. Mariana Figueroa. Dr. Figuero is a leading researcher in light and human health and the director of the Light and Health Research Center at Mount Sinai. With a background in architecture, her work explores how light affects our circadian rhythms, sleep, mood, alertness, and overall health, and how the spaces we live in and work in can better support our biology. Dr. Figueroa, welcome to Room to Think. Thank you. Thanks for having me. Before we really get into the meat of it, for a listener who's never thought twice about the light in their home, beyond just is it bright enough to see, how would you describe what you do and why you do it?
Dr. Mariana FigueiroWell, we are showing that the light and the environment you spend your day, whether it's at home, in the office, anywhere, can affect your sleep. And I think that's uh that's something that people are deeply uh concerned about because you know, sleep deprivation and bad sleep, it's something that a good chunk of people experience. And um what we're showing is that that by changing your light during the day, that you can actually improve your sleep at night. And by doing that, you then have a cascade of benefits. You improve your mood, um, you know, there's studies showing that you can you may even eat less, um, you may have you know less risk for diseases like diabetes, obesity, cardiovascular disease, and even cancer and Alzheimer's disease. Um so I think we need to start thinking about lighting as more than just vision and start thinking about lighting as uh an instrument for health. And how did you get into this? Ooh, um by accident. So, you know, as you mentioned, my my background is architecture. I was an architect, I was a practicing architect, and then I got a master's of science and lighting, which I thought I was going to be doing lighting design, but then I started um in the master's degree, I started learning about research and more specifically learning about what we call the non-visual effects of light. I mean, a lot of people don't like that word because it's really all through the retina. And the photoreceptors in the retina, they talk to each other, so it's not that it's a completely different system. There's interaction. But anyway, it's light that affects your biological clock, not necessarily light that allows you to see. So I started working, um, I did my master's thesis in looking at um light in a newborn intensive care unit, um, and how it helps uh shift workers stay more alert at night during their night shift. Um, and I really fell in love with the area. And then I got my PhD in science and moved really to research and trying to better understand lighting characteristics, lighting applications, how we could use light to improve health and well-being. Obviously, with my architecture background, I'm very focused on um how do you apply that information, not just doing the basic science, but also looking at more of the applied science. And that's really where I started working more with people in their own environments, living at home, in hospitals, in their work environments, and trying to see how we can improve that to improve health and well-being.
Lyssia KatanWell, I'm very grateful to have you here because that's exactly what we talk about: how people can actually take this research and put it into their homes and really improve their lives. Was there a specific moment where you realized that light wasn't just something we see and it was really doing something to us?
Dr. Mariana FigueiroThe
NICU And Alzheimer Care Wake Up Call
Dr. Mariana Figueiromost, I think, interesting um experience for me was during the master's thesis that I did at that NICU and South Band. Um, I was there for a month. Um, and I wasn't sleeping more than three, four hours in a row because I was running day shift nurses and night shift nurses. And I saw how difficult it is to be a night shift nurse and how hard it is to stay awake at night when your body is basically telling you it's time to go to bed, you need to go to sleep, and you're fighting to stay awake. And they had premature infants' lives in their hands. Um, and I could see that the lighting was helping them. And that's where I thought, you know what, that is an area I want to continue to do work with. And then the second project that I did right after I started at the Lighting Research Center as an assistant professor was working with Alzheimer's disease in nursing homes. And you get into the nursing home and you see how dark it is during the day and how flat the lighting is day and night. And just being able to provide them with that bright day, dark night, and seeing that that was improving their sleep, reducing their agitation, improving their mood was like the first time I left the nursing home, I almost left crying because it is it is so hard to see that it is such a simple way to improve their lives, and yet we're not doing it, or at least we weren't doing it. Um so that's when I realized, you know what, we can do something to help people. And that's when we started, you know, increasing the reach and trying to reach different people to be able to um try to expand the applications of using lighting to improve uh health and well-being.
Lyssia KatanI know exactly what you mean about the uh very harsh lighting in nursing homes. And it's really unfortunate because a lot of these elderly people can't really say much about it or can't do much about it. And it's just something so simple that do you think often gets overlooked because it's so simple, or it's just not seen as important?
Dr. Mariana FigueiroI think it is, um, I think it's lack of knowledge. I I don't think a lot of people understand the importance of lighting in general when you do construction. Um first of all, lighting is the last thing that one of the last things that people think about it. You know, they're gonna think more about their kind of materials they're gonna use in their kitchen counters than they're gonna think about the lighting, right? And I think part of it is really lack of knowledge of how important it is. And it's not just important for the health, but even for visibility. If you think about older people, that they tend to have less light reaching the back of the eye, they need more light to be able to see, to perform their normal visual tasks. We don't even think about that when we're doing lighting in spaces for the aging population, for example. Um, and there are simple changes that you can do at home, for example, that you can keep people at home longer. You don't have to transition people to more controlled environments by providing first good lighting for visibility that allows them to do things safely at home, but also the lighting for better sleep, which also allows them to sleep at home. So I I think I think it's a little bit of, you know, I I don't want to say that in a in a bad way, it's in a good way. It's ignorance, it's it's lack of knowing. Because we do take lighting for granted, right? We you don't really think about lighting. It's you flip the switch on, you see, you flipped it off, you don't see, and that's about it. So I think that the ignorance of all the the nuances and all the positive impact. Um, you know, if you don't understand the benefits, you know, why spend more or why even think a little bit more about it?
Lyssia KatanThrough all your research, did you change how you lived in your home? Like when you when you left that nursing home, for example?
Dr. Mariana FigueiroWell, yes. I mean, I I basically redid all the lighting um in my house. Um and um I do have much better lighting than the normal. I mean, things, very simple things like, you know, adding under cabinet lighting, adding up lights in the kitchen so that you have sort of a uh general lighting that everywhere you look, you're getting that lighting. Um I think the other thing that um we tend to take a lot for granted is um windows and window shades and where do you sit with respect to the window? So for example, you know, you if you have a desk here working from home, you want to sit facing your window because you want to get that light at the eye. By the way, it will look you may it will make you look better on in video because you're getting that light. That's one thing, but it will also help with, you know, giving you the light that you need during the day to improve your sleep and and maintain you more alert. Um so so yes, uh what I did in my house was really to have good lighting for visibility. Um and and I have a lot of windows and I pull up my shades, and I'm sure I get my coffee and my lighting at the same time in the morning because it's just a good habit to do it.
Light Is Like A Drug
Lyssia KatanYou have said something that I I really can't stop thinking about. You said that light is like a drug, uh, or light is a drug. What do you mean by that?
Dr. Mariana FigueiroYeah, it's interesting. It's kind of an oxymoron because it is a non-pharmacological drug, right? So it's it's not really a pill you take, but it does have an impact in your physiological system very similar to um what drugs have. Um so you can, depending on when you get that light, you can actually improve your sleep. But if you get that light at the wrong time, like if you get it at night, in the evening, before going to bed, it can actually disrupt your sleep and disrupt your circadian system. So the reason why I like to say it's like a drug, it's because if you think of a medication, your physician is never gonna tell you, yeah, just you know, put a bunch of them and just take them anytime. They're gonna give you a dosage, a time of day, um, how often you need to take it. So they're gonna give you a sort of a recipe or prescription for how to take that drug. Um, we don't do that with lighting, right? We don't even measure how much lighting we're getting. Um, we don't control anything that we're receiving. Um, so I think we should treat it more like a prescribed thing where we know when to get it, how much to get it, when to avoid it, um, how often you get it. Um, because one of the things about the benefits of lighting is also regularity. You know, you hear a lot medication. Don't take the medication one day in the morning and one day at night. Take every day in the morning. It's it's the same thing with lighting. You have to have that sort of prescribed dose to have the benefits of it. Um, so I think that that's where I see it as a drug. But the benefit of it too is that it's a non-drug. So that's that is also something very good, especially for people that are already being treated for something like cancer patients we're working with, Parkinson's disease patients, Alzheimer's disease patients. These people are already over medicated. So if we can give something that would help them without being necessarily a pharmaceutical, that's a good thing.
Lyssia KatanYeah, absolutely. And and you uh you've done a lot of very interesting work that I would love to ask you about.
Submarines And A 24 Hour Body
Lyssia KatanYou worked with the US Navy on submarines. What was that like?
Dr. Mariana FigueiroIt was actually very interesting. I visited the submarine and I said, first of all, I'm too tall for a submarine and it's too close. So it's like too tight. So I've been there once and I don't want to be there again, but we did very interesting work with them where we changed the lighting in the submarine. We changed two things there. Uh one was um they they have an 18 in general, they used to have an 18-hour schedule instead of a 24-hour schedule. And that was very hard for them because we are 24-hour species, right? We're our biological clock runs with a period close to, not exactly 24 hours, but close to 24 hours is about on average 24.2 hours. Um, and what lighting and morning lighting does, it resets your clock so that it runs with 24 hours every day, so that it's synchronized with your watch. So being able to synchronize to an 18-hour schedule is very hard. It's almost almost impossible to do. So that was very detrimental to them. So the first thing that we work with them was let's change the schedule to 24-hour schedules. Instead of, you know, 666, we would do uh 888. So it would be three shifts of eight-hour schedule. So that would be better. So they are eight hours on duty, eight hours still awake doing things that are not necessarily on duty or administrative things, and then eight hours sleeping. Um, that was the first thing. And the second thing we did is obviously inside a submarine it's flat, right? It's constant light 24 hours. And we are really designed to see bright and dark, right? Um, so the way we did is we changed the lighting so that they were receiving that bright and dark in their respective shifts. So it's a way to help them maintain entrainment and alertness into the shifts. And we saw very positive impact on biomarkers. So we measured their melatonin levels, and we were seeing that the melatonin levels were higher during the nighttime, which was which is what you want so that you can sleep better. Um, they improved the performance, even though there was obviously because of the design we had to do and the restrictions we had, we couldn't really counterbalance. So there were some practice effect in the in the performance, but there was a it was looking like they were doing better. But most important, they were sleeping better. They were reporting that when they were in the bunkers to sleep, they were sleeping better. And that's really what matters because if you sleep better, you will do everything else better when you're awake. So that was a very interesting study. Um and you know, I think uh we we like to believe that we helped the Navy uh with a little bit of that, and I think we did. Um and you know, they I don't know how much they made the change to all the other submarines, but at least we gave them some some food for thought there.
Lyssia KatanThat
Brighten Your Days At Home
Lyssia Katanis absolutely fascinating. The fact that you're able to improve the sailors' lives in a submarine where it's super dark under underwater, there's no light. How can someone take what you did in the submarine and in your work and apply it in their own home? Where where do they even start?
Dr. Mariana FigueiroI think they start by increasing the amount of light they are exposed to during the day. Um the the beauty of being at home is like you said, in the submarine, you can't open up a window. You can do that at home. Um, so just you know, nowadays there's so much um controls and so much that people can do it in automation, right? So if you can't afford to do that, just make sure that your shades are up, your um, you know, your your windows are you're close to your windows, um, you face your window, so that's one thing. If you can't do that, because unfortunately you're stuck working in a basement without a window, which may happen to a lot of people that are now working from home, you can increase the amount of light that you're getting. Now, it doesn't necessarily need to be coming from the ceiling. It could be that you're putting task lights that are actually facing you without creating a lot of glare. So you want to you wanna make sure you're not looking at the direct bright uh bulb. So you want to have diffusers that will diffuse that light, but at the same time will illuminate your entire face because what matters for your biological cloud is the light reaching the back of the eye. Um so whatever you do, you want to get that light reaching the back of the eye. And and you we have something in lighting, we call it inverse square law. So basically, is the closer you get the source, the higher the amount of light that you get. So if you can get that source closer to your eye, then um you don't need as much light level to increase that much the light level to be able to receive the dose that you need to receive. So I always tell people, I mean, things around, you know, maybe lighting around your computer screen, maybe table lamps on both sides of your of your uh computer work. Um if you're sitting and reading something, turn on a couple of table lamps or floor lamps very close to you. That those are things that you want to increase that light level, especially in the morning hours. If you can go outdoors, by all means do it. Half an hour walk, it's great. If you can sit outside for a cup of coffee, even better. You can't do that a lot in hot summers days or you know, cold winter days, but going outside is always perfect, right? You have the exact dose that you need in the morning. Um, but at a minimum, increase that light that you have during the daytime hours and try to minimize it a couple of hours prior to your bedtime. That that's really sort of a very simple recipe for helping with your health and well-being.
Lyssia KatanWhat
Stop Overfocusing On Blue Light
Lyssia Katanabout the quality of the light? Because we've all heard the the different lumens and the red light and the blue light. Does any of that matter when it comes to the research?
Dr. Mariana FigueiroWell, um, you know, you have what we call lighting characteristics. So you have the amount, you have the spectrum, which is the color, uh, you have the timing. Um, you know, when are you giving it? Morning, evening, afternoon. Um, you have the duration, how long are you giving that light? Right? And then you have what we call the distribution. Is it a direct light? Like when you have a recess scan, right, direct your your workstation? Is it a direct indirect? Does it bounce light off, and so on? So, in terms of the amount, you know, in general, you Think about a light bulb that you normally put at home just to give you an idea of quantity. A light bulb, a 60-watt incandescent, which now is probably 15, 20 watt LED, gives you about 800 to 1,000 lumens. You need to have a bulb that will give you at least 3,000 lumens. Okay, whether you do two or three of the smaller light bulbs or you find a lot uh a bigger light bulb, that's pretty much what you're looking at in terms of the lumens. Now, obviously, lumens alone doesn't matter because if you put these lumens too far away from your eye, like I told you with the inverse inverse square law, you're losing all that light. So you want to make sure this thing is an arm's length of um, you know, of you. So whatever you put is no more than an arm's length, right? And that you're probably getting the amount of light that you need. That's the most important lighting characteristic is how much light you're getting. Okay, light level. If you have one thing to change, change the light level, okay. The second thing is the spectrum. And there's a lot to that people talk about that. Oh, we need bluish white light in the morning, and we need yellowish in the evening. Sure, it helps, but most of our studies we're doing right now, it's all warm color lights. It's 2700K or 3000K. So it doesn't have to be bluish white to have an effect on the circadian system if you have it bright enough. And and that's that's uh an information that I think designers welcome because nobody likes the harsh bluish-white light, right? So so so that's the one thing to keep in mind. You don't have to have the bluish, you know, awful white, very, you know, sterile color type. So that's the second thing. The third thing is you you want to do it in the morning within two hours of waking. Okay, that's the good light for in training your circadian clock and helping you with sleep better. Now, light at any time of the day will be alerting. So it's like a cup of coffee. So you have two things that light can do for you. One is that morning light that will synchronize your biological clock to your watch. And one is at any time of day and night, and the work that I did with shift workers looking at night shift, it's like a cup of coffee. It's an alerting effect, okay? But for entrainment, morning light is the best. And then the duration, you want to do it for at least an hour in the morning. Um, if you go outdoors, because it's so much light, you can probably reduce that to a half an hour walk. If you're indoors, you're never gonna get as much light as you get outdoors. So you want to extend that duration to compensate for that lower light level. Um, so that's sort of the dose, and that's sort of the characteristics. Now, obviously, quality is important in terms of, you know, color rendering, how it renders color. This is all very important, more for visibility than it is for the circadian system. Um, but you want to have that as well because that same lighting is helping to illuminate the space and helping you see tasks and so on. Um, but for the circadian, it really is a mount. That's one of the most important sort of characteristics of life. The other ones are also important, dose is important, so on. Um, but I think people talk too much about spectrum, and that's probably not the most important one.
Lyssia KatanWhat about all the gadgets that they're selling? The blue light glasses and the screen covers, and is that actually important or not really?
Dr. Mariana FigueiroI always like to say that it depends. Um, I have to say that a lot of what you see in, you know, um Amazon and selling all that stuff, wherever, um, a lot of it it's probably overselling. Um, I think that um we did a study with the night shift mode from the Apple. Um and what we found is that yes, if you move to a more yellow screen where you're removing the short wavelength or the blue light, you do have less of an effect on the circadian system. And we measured by melt on production. Um but if you don't reduce the brightness, you still have an effect. So you have to actually reduce both. You have to make it warmer, but you also have to reduce the light level. And sometimes these devices only do one, they don't do the other, right? So so it it's hard to say it's good or bad. You really need to test it out before you you just go all in. Um so one of the things that I always tell people is it it is a lot about what you're doing on your self-luminous displays, right? You you can you can remove all the light and all the blue light and not have an effect, a physiological effect on the circadian system, but that may still be alerting, and that may still make it hard for you to go to bed, right? Because you're excited about something. Um, because sleep has multiple inputs, right? And and you may be taking care of one with these filters, but you're not taking care of the other ones. So while I don't want to condemn all of the filters and all of the gadgets, because I think you know, I I like to test these things before I say anything, what I would say is um it first of all, it has to be clear what exactly they're filtering out. Um and I think there needs some testing to see if it really affects your biological clock or not. And a lot of times, even if it improves the effect or reduces the effect on your biological clock at night, it may not resolve the problem of sleeping, for example. So I think it's a complex uh and and the other thing that I think it's important to point out is if you're exposed to a lot of light during the day, you're less sensitive to light in the evening. So these filters may be less effective than if you're in a dark room all day, that light from the self-luminous displays may have an effect on you because you know your your system readjusts. So it's hard to say good or bad without, but I would say caution as a, you know, don't go all in, make sure you do your homework, um, and and look at the the specific conditions, and it may or may not help.
Lyssia KatanThat's that's a really good point because most often we think of of the light or the blue light glasses, but if you're getting a really emotional text message, you're not gonna be able to sleep, regardless of how dim your screen is.
Dr. Mariana FigueiroIf you can't pay a mortgage, there's just nothing you can do about the lighting, right? It's like you're just gonna stay awake at night thinking about that. So that's that's what I tell people is that it's it's it's it is an interaction. You can't just isolate one thing and and assume that it will solve all the problems.
Lyssia KatanOr get frustrated when it's not working. Yeah, that's right.
Measuring Circadian Effective Light
Lyssia KatanSo you and Dr. Ray created a way to actually measure whether the light in a room is reaching that system, the circadian stimulus. Uh, in the simplest of terms, what does that let us know that a normal light meter couldn't?
Dr. Mariana FigueiroYeah, it's uh basically um the circadian system is um influenced by um you could say three types or five types of photoreceptors. So you have the rods and three types of cones, the short, middle, long wavelength cones. And those are really visual photoreceptors. So the cones are daytime vision, the rods are nighttime vision. Um and then you have a new sort of set of uh photoreceptors that was discovered around 2000, and actually some of the research, even in the early 90s, were suggesting that yes, and that was research from Russell Foster in England that suggested that mice that didn't have rods and cones were still responding to light for the circadian system. And um, and then in in 2001, David Bur, it was 2001, I believe, yeah, David Berson discovered this new class of photoreceptor that we call intrinsically photosensive retinoganglian cells. Now, what's interesting is that this photoreceptor is what basically conducts the signal from the retina to the biological clock, but they also receive input from the rods and cones, from the classical photoreceptors, right? So they basically gather everything and then transfer that information uh to the biological clock. So what we did with the circadian stimulus is really looking at how these photoreceptors in the retina combine those light signals into neural signals for the circadian system. So it's really looking at, I like to call it circadian effective light. So it is the light that actually affects your biological clock. So that's what the, you know, and it and it is a mathematical model that you use the spectrum of light, the amount of light, you combine these, and then you get to a response. And then we also developed what we call the day simeter, which is a really a personal light meter that you use, say, as a pendant, to that it's calibrated to measure that light that affects the circadian system. Because, you know, this one thing about our um physiological system is that you get in the room, it's dark, you know it's dark, you turn on the lights, so you have that instinct. But you don't have that ability to know if it's dark for the biological clock. It's not like hunger, right? When you're hungry, your trauma, your stomach, you know, growls, and then you're like, okay, I should eat because I'm hungry. Well, there's nothing in the biological clock that tells you, oh, I'm desynchronized, I'm not getting enough light. So you don't have that, right? So our idea was if we can at least measure what people are being exposed to and characterize the built environment, we can at least give some recommendations for change. And that's what we did with the Day Cimeter, which um it's a funny story about it. It's called De Cimeter because at the time we wanted funding to develop the device. Um, and Department of Energy said, we don't fund health, but we're interested in daylight. Um, so it said, hey, we can come up with a device that you can measure how much daylight you have in the space. So it's gonna call decimeter, and you know, haven't memorized how much daylight you're getting in the space, and that's the decimeter. And then we ended up getting a grant from the National Institutes on Aging to develop that more for Alzheimer's patients as a tool to basically show that they're not being exposed to the light they need and try to change that. And that's cascaded in all the work that we we have been doing it. So so that was the purpose of developing that. It's being able to measure what circadian effective light is, and then create a device that can measure that circadian effective light.
Lyssia KatanSo very cool. So so is it true that a room could be very bright when you walk in, but actually biologically not very bright at all?
Dr. Mariana FigueiroIt it is true. I mean, I wouldn't say very bright, but I would say bright enough for fission. So one example I like to give is uh watching TV in a dark room. It looks pretty bright, right? I mean, your TV looks pretty bright and so on. It's very ineffective, physiologically ineffective for the circadian system. Uh, first of all, you're not watching your TV very close to the TV, and just like I said, just the distance, just reduce that amount of light. But your visual system, it looks like it's pretty bright. Some of these TVs look pretty bright, but they don't have an effect on the biological clock. But, but, but they can keep you awake if you're watching that funny movie. And, you know, so don't forget that. Um, but yes, uh that's a great example where you look at it and and even night lights, you know, when you wake up at night that you're dark adapted, um, your room looks pretty bright. Um, you can navigate in the space just with a small nightlight, but that's completely biologically dark for you. So, yes, um I would say a great example of that is nursing homes. You get in, you can navigate, you see everything. It's like daytime there, but it's not necessarily biologically active.
Lyssia KatanYou've
Aging Sleep Cognition And Falls
Lyssia Katandone work on older adults, and as someone ages, it lets in dramatically less light. So a senior can be sitting in a room that looks pretty bright, but is actually biologically in the dark. What does that do to them over time?
Dr. Mariana FigueiroUm first of all, sleep problems. That's probably what you're gonna start seeing very, very early. Um you can start getting, you know, as a the the sleep problems are likely a result of um lack of circadian entrainment. So basically they're desynchronized, and what's gonna happen is they're gonna start staying awake in the middle of the night and taking naps during the day. Um and that sleep and circadian disturbances has been linked to, I think for the aging population is cognition issues and even increased risk for dementia um, you know, in the long run. So I I'm a huge proponent of you gotta get older people outside, or you have to, wherever they stay during the day, increase that amount of light. I mean, we just published a paper where we showed that by giving them that extra light during the day, that they're improving cognition. Um, so you see an improvement in cognition, you see an improvement in sleep, um, you see an improvement in mood. And we are finishing up a project where we're looking at MRI and we're seeing changes in the brain due to that light exposure. Um, so it is definitely beneficial and it's definitely detrimental uh not to get them on bright uh days.
Lyssia KatanThat's interesting because I've heard similar things about um hearing aids. And as someone ages not being able to hear, actually their brain stops trying to figure it out what what they're hearing. Is that similar with light where they just kind of stop seeing, or does it affect a different part of the brain?
Dr. Mariana FigueiroNo, I I I I think um there's a couple things. There's obviously I think there is a a direct impact because you know, and but that has more to do with the visibility part. So, you know, your core your visual cortex is 80% of your sensory stimulation. So a lot of what you do is through your visual system, right? Um, and and actually one area that I didn't mention, but we have been working on is false. So as you get older, um your your visual system, it's actually providing even more information to your perceptual system to help with postural control and stability. So I I use the example, and I always do that when I'm teaching, and the kids are quiet when I ask them the question is when you're drunk and you close your eyes, it gets worse. You get dizzier. And the reason is that you lost that visual information that it's helping you maintain your postural control and stability. You close your eyes and it it get, you lose that. And that's in a way, that is what happens with older people. When they lose that ability to see, they will lose that information to their perceptual system, and that may impact their ability to maintain postural control and stability. So one of the things that we're showing is that if you give them horizontal vertical night lights, that gives you the cues of what's horizontal and what's vertical, it actually helps them when they get out of bed, it increases that uh postural control and stability. So we we um we um installed some of these lights in nursing homes, and we saw a 34% decrease in false uh incidents just by having this horizontal vertical night light. So back to your original question was what happens to them? Well, it may happen that they, yes, they do, they can get sleep disturbances, which can cascade in a lot of things, but there's also visibility, and it could be that the brain is just not it's just not using that as much. And then you have the other parts of the brain that the visual system feeds into it, that you lose that information as well.
Lighting Help For Alzheimer Caregivers
Lyssia KatanFor people who are living with individuals with Alzheimer's, uh perhaps in their house, um for or for a family caring for a parent at home, what could they actually do to change a light to potentially improve their family members' mood or irritability or general demeanor?
Dr. Mariana FigueiroYeah, they can um add more lights near where they spend, especially their morning hours. They can bring them outdoors, um open up shades and windows, um, and keep that regular. That's one of the things that it's most important is that do that every day at the same time. If you're gonna take them out for a walk, do it every day at the same time. If you're gonna put them in an area that is brighter, like a sunroom or whatever, try to do it every day at the same time. So the regularity is very important for the Circadian system. And that's what you you want to try to do. We had a case where Mark Ray, who who works with me, um gave a lecture and there was this woman that was in the audience, her husband had Alzheimer's, and then I guess two years later, she contacted him and she said, you know, I attended one of your lectures, and you said you have to get more light during the day, and so on. So what I started doing is I started driving around LA with my husband so that he was in the car and he was getting that light during the day. And I can't tell you how much he improved. And it was very nice. I mean, I honestly don't know that I would want to be driving in LA for that, maybe, you know, staying outside walking. But that might be the way that he she got him entertained, you know, to be not agitated and so on. But I thought it was, it was uh it was just an interesting story, but it's it's basically saying if you do this every day, you give them that increased amount of light, you're gonna see benefits. You're definitely gonna see benefits. And it's cumulative. It's like we've seen, we've studied people for six months, and we see that they continuously improve. Um, so we're not curing Alzheimer's, they're gonna still gonna have the disease, but what you're doing is you're treating a symptom. Um, and I think that a lot of times this is what medicine does. Medicine will treat symptoms, right? So, in a way, that's what we're trying to do with lighting.
Morning And Evening Lighting Recipe
Lyssia KatanIt really is a drug, like you said. Yeah. So when we get practical, if you can, can you walk me through the ideal first hour after someone wakes up and what they should be doing with the light, specifically to set their whole day right?
Dr. Mariana FigueiroFirst thing you want to do is get up, open up your face, increase that amount of light in your bedroom. I know you're gonna go to the kitchen and get a cup of coffee, go for it, because I wouldn't tell you you you don't need your cup of coffee because I think you do. But sit by a window to read the newspaper, turn on if you sit to read the newspaper, or if you sit by your computer to do your um email or whatever, make sure you turn on two lives that basically. Flank your one on each side, your your face, so that you're getting that light. If you sit by a window, make sure you're facing the window. You're not with your head against the window. Um, and be there, or if you can go for a walk, go walk your dog. You know, I I I had a student that once came up with an idea that I thought it was brilliant and said, the best thing you can do is get a puppy, because the puppy's gonna get you out of bed every morning, it's gonna have you walk outside every day at the same time. And it's a perfect thing to do. So if you have a dog or a puppy, go for a walk outside because that's the best you can do. But yes, for the first hour after you get up, you do want to increase that amount of light. I mean, a lot of people will have to get up and take a shower and be in their bathrooms. Retrofit the lighting in your bathroom so you have actually more light in your bathroom. Maybe you can have, you know, shower lights, something that, you know, it's a it's a vertical surface in your shower. So wherever you're gonna spend the first hour of your day, you want to increase that amount of light as much as you can. Um, but my recommendation is go outside for a walk, go walk your dog, um, or you know, go do your reading or whatever by a window or by a place that you can turn on at least a couple of additional table floor lamps around you.
Lyssia KatanAnd what about at the end of the day, from dinner until sleep? What should be going on at the light?
Dr. Mariana FigueiroYeah. And this is very important because it's not just the amount of light you get during the day, but it's also the amount of light you get prior to bed. So a couple of hours before your bedtime, you actually want to do the opposite. You want to turn off those additional lights. Um, you still want to have your regular table lamps, that they're typically not as bright. Um if you're gonna read in bed, um, ideally not on self-luminous displays, but if you do, I recommend at least an hour, ideally two hours before that you turn it off, dim it down at least at a minimum. Um and if you're gonna read a book, try to focus the light on the book, not necessarily in your eyes to minimize that. Um, watching TV is fine. Um again, it's it's fine for the lighting, not for the uh yes. I think that the difference with a TV and an iPad, for example, is that the TV is far away. The iPad is really close to your eyes. Again, it does not mean that that iPad will affect your biological clock. But but if you didn't get enough light during the day, it may have. And it we showed that after two hours of exposure, you may have a small effect on the biological clock. So it's if you're gonna do it, do it for 15 minutes. Don't do it for two hours. Um but yes, um uh two places in the home that tend to be brighter than normal, that you may want to think about having layers of light is the kitchen and the bathroom, right? So with the kitchen, you may want to consider having more of under cabinets, uh toe lights, um, indirect lights that you can dim it down, or just leave the under cabinets light on at some point, or turn, you know, dim down a little bit. So that's in the kitchen. And then in the bathroom, you want to minimize before you go to bed to turn on those very bright vanity lights. You don't need that to brush your teeth. You need that to put makeup on, and that's not what you're doing before going to bed. So try to reduce that. Try to turn on the lower lights um in the evening than having you know very bright lights in in your bathrooms. Um, so that would be my recommendation. But I think that honestly, we talk too much about light at night, and I don't think we talked enough about light during the day. And I think that if you increase the amount of light you get during the day, you are minimizing the risk of the light at night and have a more harmful impact. And I think we need to keep that in mind. It's bright and dim, is the contrast.
Lyssia KatanI'm a huge proponent against TVs in the bedroom. So I just I can use your research as like as to make my
Red Light That Boosts Alertness
Lyssia Katancase. But um, so if a what about what about red light? I just I wanted to ask that because have you worked with red light? And red light therapy seems to be very popular these days.
Dr. Mariana FigueiroYeah, um, I have worked with red light um a lot, but not with a red light therapy the way they're working nowadays, which is looking at a you know, ATP production and mitochondria, and some of these masks that are being sold online is like you're gonna have 10 years younger, and um don't get me wrong, there's research on that, and I think there's science behind some of those things. What I think that I'm more skeptical about, the products that are being sold online, is I don't know what the dosage that they're delivering is. And I think that's what I would caution. Um, that there is research about red NIR and mitochondria and the positive impact on things like you know, skin or even um uh wound healing or, you know, um muscle fatigue, all of this are there's research on that. And and I me personally was we're just starting to get into that kind of research. But the red light that I have worked with, it's been really red. And if you ask me what was the most surprising uh findings that I had in my research, I can tell you was the work that we're doing with red light, because red light does not affect the biological clock. So everything that I told you about circadian and trainment helping with sleep and so on, nothing. Because you the photoreceptors in the eye do not respond to that red light for the circadian system. So it's almost like ineffective, or to be effective, the amount of light that you need to give is so high that you normally don't get that. So in one of our studies, we used the red light to compare to the blue light, which we knew was circadian effective, as a placebo control. And we started getting an alerting effect. We were measuring EEG, we're measuring subjective sleepiness, and it was just as alerting as the blue light. And I'm like, and at the time Mark said, you're doing something wrong. Repeat the studies. We kept repeating, and we kept getting it. And I'm like, there's something here. So I like to say that it's like a cup of coffee, and that red light, and and that's the application we've done a lot of studies with NIOSH looking at shift work is how do you give that red light to increase alertness without affecting melatonin levels, without affecting the biological clock, because that's what you want for shift workers. You want to keep them alert, but you don't want to mess with their biological clock. And we also did some work with the afternoon post-lunch dip. You know, everybody has their slump in the afternoon. The red light is extremely effective at helping with that. So the work we're doing with the red light is really looking at the alerting effects. Um, and it is it's real, it's very real. And um, we had a lot of skeptical people, but we have published now six or seven papers. We've done work in the field, and it's it's there. The effect exists. And so trying to understand what are the mechanisms, that's something that we've been doing now. Um, and and you know, sleep has sort of two components. One is the circadian, where you're alert, awake during the day, and asleep at night, but the other one is what we call homeostatic sleep pressure. Um, and that homeostatic sleep, uh, we think that there might be an interaction with light into that homeostatic sleep, which it helps with reducing a little bit that sleep pressure. It's like what coffee does. When you have that sleep homeostatic pressure, you produce what we call adenosine. And what coffee does, coffee blocks the adenosine receptors in the brain. So it's almost like fooling your brain so that you don't perceive that you have that sleep pressure. We think that the red light is doing similar things, but this is still research in progress.
Bright Days Dim Evenings Dark Nights
Lyssia KatanVery interesting. Absolutely fascinating. If you look ahead, 10, 20 years in the future, how do you hope the way we light our homes and our offices, our hospitals evolves to actually support the humans that live inside?
Dr. Mariana FigueiroIn very simple terms, bright days, dim evenings, dark nights. Um I think we need to change the lighting so that this is just normal. Um and we don't have that. We literally have flat light. Um, you know, we turn it on during the day, it's probably not as bright. And we keep it on in the evening, which is probably too bright for the evening. So I think changing that practice, um, I think we'll make a world of difference. And it's a simple way, it's not complicated.
Lyssia KatanYeah. We tend to overcomplicate things. If a listener was to forget everything they heard in this conversation except for one thing, what would you want it to be?
Dr. Mariana FigueiroYou need brighter days. That's you need to get more light during the day. If if anything, just do that. And I think and and be regular. That's the you know, regularity and bright days are important.
Lyssia KatanDr. Figueroa, thank you so much for anyone listening. Where can they follow your work and and see what's next?
Dr. Mariana FigueiroWe have a website where we put everything on it. Um, it's just um I I don't remember the the URL, but if you if you Google Latin Health Research Center and Mount Sinai, we're the first one that show up. Um and we have yeah, we have all of our research there. Um, you know, we're obviously federally funded, so we're we're open with, you know, we talked about circadian stimulus. We have like a calculator there that you know how much circadian stimulus you can get out of different light sources and so on. So um everything is online, so it's all freely available.
Lyssia KatanYour work is is absolutely fascinating, um, illuminating, if you will. And I'm so absolutely grateful for your time. I'm honored to have you on the podcast. And I really know our listeners will get so much out of this episode. Thank you so much for your time and uh and for your research. And thank you for having me. It's a pleasure.
Where To Follow And Closing
Lyssia KatanThank you so much for spending this time with me on Room to Think. If you enjoyed this episode, feel free to follow the show, subscribe, leave a review, and share it with someone who you think would really appreciate a more thoughtful approach to their space. You can find more Design Meets Psychology insights on social, in our community, and definitely in upcoming episodes so you can build a better life by design. Thanks again for listening. I'll see you next time.