Bright Days, Dark Nights
Date Published: January 12, 2022
Mariana Figueiro, PhD, is director of the Light and Health Research Center at the Icahn School of Medicine at Mount Sinai. She studies how to use light to improve human health, including for patients with Alzheimer's, cancer, and Parkinson's. On Road to Resilience, Dr. Figueiro explains how to use light to sleep better and feel more alert during the day, including tips on digital device use. She also has specific advice for shift workers.
From the Mount Sinai Health System in New York City, this is Road to Resilience, a podcast about getting through the hard stuff. I'm Jon Earle. My guest today is Dr. Mariana Figueiro. She's Director of the Light and Health Research Center at Mount Sinai. Dr. Figueiro and her team research how to use light to improve human health, including for patients with Alzheimer's, cancer, and Parkinson's. In our conversation, she talks about how our bodies are designed to respond to natural light, how modern life gets in the way, and what we can do to bridge the gap. She also offers specific advice for shift workers on how to use light to stay alert and transition between day and night shifts. So here is Dr. Mariana Figueiro, enjoy! Dr. Figueiro, welcome to Road to Resilience.
Mariana Figueiro, PhD:: 00:49
Well, thank you very much. Thanks for having me.
As I was preparing for this interview, I was thinking about your sensitivity to light. And I suspect that your spaces and even your daily routine is much more intentional than the average person's with regard to light. And so I was wondering if you could just start by taking us through what happens—you get up first thing in the morning, how does your light routine unfold from there?
Mariana Figueiro, PhD: 01:17
Open up the shades. That's the first thing. Let daylight come in. Because that is the first cue to your body to tell you it's daytime, it's time for you to get up. It's time for you to switch from a nighttime person to a daytime person. We all need that morning light. I mean, and that's really one of the hardest things about winter is when you have to wake up and it's a dark room. And what I like to do is I like to have lighting in my bedroom that actually allows me to not wake up in the dark. So brighten up first thing in the morning. That's the first thing I like to do.
Wait, so go into this in more detail. Why is it so important to get that blast of natural light first thing in the morning?
Mariana Figueiro, PhD: 02:04
We have a biological clock in our brains and this clock runs without any signal from the external environment. So if you're in a dark cave and you have no access to any light, any watch, anything, you're still gonna have the biological clock that's still gonna run. But the difference is that it runs for a period slightly longer than 24 hours. So on average, the clock runs with a period of about 24.2 hours. So what that morning light does is it resets your clock, your internal clock daily, so that you now run 24 rather than 24.2 hours. So you're in sync with your watch. If you don't have that, you're gonna slowly be delayed with respect to your watch. So your watch says it's 7 a.m., your biological clock says it's 6:50 a.m.. Tomorrow's gonna say it's 6:40 a.m., the following day's gonna say it's 6:30 a.m.. So you can see how hard it is to get up.
So the problem would be that you would gradually become more and more out of sync?
Mariana Figueiro, PhD: 03:12
That's exactly right. So you need that daily signal so that every day you're resetting the clock, because the clock resets and then it slowly goes back to being slower. So you have to give it that punch again. So that's what you need daily.
This is maybe a very obvious question, but why is it important to be in sync with the clock?
Mariana Figueiro, PhD: 03:39
It's a very good question. If you have control of your own life, it probably isn't. So if you can work at three in the morning, instead of three in the afternoon, that's fine. You could do that. But we have social obligations. We have to be at work at certain times. We have to be at school at certain times. And that's really what presses us to be in sync with the watch.
That makes sense. So I need that blast of blue light the first thing in the morning. Something that was so interesting that you said to me when we spoke earlier was the difference in intensity between natural light and artificial light, the sort of light that fills our indoor lives. Can you tell me about that?
Mariana Figueiro, PhD: 04:29
Yeah, you said that we need blue light, but it's not just blue, it's bright. That's what we need. We need bright days and dark nights. Okay, and to give you an idea of how dim the built environment is, when you're outdoors in the middle of the day on a bright, sunny day, you're getting about 100,000 lux, which is a unit of light reaching a surface. When you're inside, in an office, you're probably getting 200-300 lux, max. So, it's 50 times less, it's a lot less light than what you get [outdoors]. Now what's really fooling ourselves is that your visual system is very sensitive to light. So the space doesn't look dim to you. In fact, in a lot of offices, people complain that it's too bright and it's not even close to what you get outside. But your visual system has the ability of adapting to this really wide range of light. But your biological clock, it's not as—it is adaptable, I'm not gonna say it's not adaptable, but it's not as adaptable as your visual system. So your visual system fools you into thinking that you have enough light and you really don't.
Do you ever feel like a canary in the coal mine?
Mariana Figueiro, PhD: 06:02
When you walk around in all the spaces that we encounter—not just our offices, but going to the supermarket, going to the barbershop, all these places that are lit in wildly different ways. It must be very disappointing to you.
Mariana Figueiro, PhD: 06:15
You know, it is. Very, very few spaces that I come in and I said, wow, that's really nice. I do have to say a lot of the spaces that I have the "wow" factor are spaces that have a lot of daylight. Now there's a difference. There's a lot of daylight, not a lot of sunlight. And I think people confuse a little bit of that. You wanna have diffuse light coming in. You don't wanna have direct sunlight coming in, because people actually won't accept direct sunlight in the space. If there's direct sunlight coming in, they will pull the shades down. You're not gonna see anything. So it's the diffuse light that is really nice. I added a bunch of lights in my office, so I guess I'm going back to the first question you had, you know, I start my day with opening up the shades and trying to go outside as much as possible in the morning. But light, it's not just that morning light that you need, you need light at any time of the day to keep you alert. So light also has almost like a cup-of-coffee effect. So it synchronizes your clock to your watch, but it's also a cup of coffee. So you need really bright light all day in a way. So I got in my office and it's very interesting. During the summer it was okay because I have a big window, thank goodness. I'm blessed to have a really nice office with a big window. So during the summer it was fine. There was a lot of light. But when it started getting around October and I would come in in the morning, I would turn on the lights, I'm like, ugh, it's just dark here. So I started bringing in the lights that I'm using in the research that I'm doing and just putting them in my office. I get people making fun because we built the lights. They're not commercial lights, they're lights that are built for research purposes. So they're not pretty or anything like that. But they're useful. They're good. They're bright. So I brought, and there was one that's like strips of light that you just face them to a wall and what it does, it reflects that light back from the wall into the space. So it kind of floods the space with light and, you know, some people pass my office and say, oh, that's nice, but it looks like landing lights, you know, because they're strips. So they're not pretty, but they're—and then I turn them off and I say, look at the difference, and they said, oh yeah, it does make a big difference! And then I added another one next to me. And I have like four types of light in my office. My office is gorgeous in terms of how bright it is. And people come in and some people don't even notice, but some people come in and say, wow, it's nice here.
I feel alert.
Mariana Figueiro, PhD: 09:12
I know, it's just nice. But it makes a big difference for me. It does make a big difference. So I mean, wow, we're in such dark environments all day long that it's just, I wish people paid a little bit more attention to it.
We started off this conversation talking about the importance of bright natural light in the morning. And we talked about the shift that can happen, that small shift day after day, where people can become out of sync with the clock that we all live by, as opposed to the natural clock. But there are many serious consequences to our lack of proper lighting. Can you go a little bit deeper into that?
Mariana Figueiro, PhD: 09:55
Yes, there is. So, you know, you can start by very small things—like you get sleepy during the day, lethargic. I hate to say it that light improves productivity, because I gotta tell you that this is sort of the holy grail of lighting is that everybody wants to show that lighting has a direct impact on productivity. And I can tell you that I don't have research showing that there is a direct impact, but I can tell that indirectly I know it impacts productivity. And the reason is that we do have research showing that it directly impacts how you sleep at night. So by being exposed to low-light levels during the day you sleep worse at night, you sleep worse at night, you will perform [worse], right? You know, I always say A equals B, B equals C, therefore A equals C, right? I've never done A equals C directly, but I can draw the length there. So that's short term. Now, if you do it long term, and you think about shift workers who are really a poster child for what we call circadian disruption, which is really what happens when you don't get that regular entrainment.
I'm sorry, what is entrainment?
Mariana Figueiro, PhD: 11:15
Oh, yes. Entrainment is that synchronization of your biological clock to the external watch. So if you don't get that regular morning light, you lose that entrainment and that will lead to circadian disruption. And circadian disruption has been linked to diabetes, obesity, cardiovascular disease, and even cancer. And in fact, shift workers are at higher risk for breast and colorectal cancer and even other types of cancer, but there has been a lot more work on these two types of cancers. And one of the hypotheses is because they're chronically disrupted, right? Because they're jet-lagging themselves every week by working for two to three shifts and then staying on dayshift three or four days, then going back to nightshift two or three days, and that's not a regular pattern. And that is what can happen. So the first thing that you're gonna see is disruption in your sleep. And then from there you start seeing long-term consequences, you start seeing more serious health effects.
I know you've done work with Alzheimer's patients. And I think that is really a great illustration of how powerful light can be.
Mariana Figueiro, PhD: 12:35
Yes, I have to say this is one of the—the two areas that I love most about the research is Alzheimer's disease and cancer. In the Alzheimer's disease, these are patients that tend to be—you know, sleep is now seen as a risk factor for Alzheimer's disease, but sleep disruption is also, actually I should say sleep disruption is a risk factor for Alzheimer's disease, and sleep disruption is also a symptom of the Alzheimer's disease itself. So one of the main issues with these patients is that they're as likely to be awake as they are to be asleep. So they don't have a consolidated eight hours of sleep at night. So they are sleeping for three hours, awake for four hours, and sleeping again for two hours. And that's obviously very hard on caregivers. So if you're a caregiver, you're trying to have a normal life, and then you have, you know, your spouse or your parent up at night, that's extremely hard on them. So, one of the things that we did is we actually went into nursing homes, which has, like I said, a constant dim light, and that's constant, it's 24 hours dim light. You don't turn off the lights at night, and you don't turn them up or on during the day, it's just constant dim light. And they suffer even more from that sleep disruption. So what we basically did is we added more lights during the day. So we increased that light-dark pattern. We made it more robust. And it's incredible, the results. We're seeing a significant improvement in their sleep. So they're staying asleep much longer. That's helping them reduce agitation and that's also helping with reducing depressive symptoms. So it's actually pretty amazing, the impact that we're seeing. And what's most interesting is that we did a six-month study where we kept the lights on for six months, and we saw that continuous decline in sleep disruption in depression and in agitation. So as I say, six months in the life of an Alzheimer's patient, it's bad, because you're getting worse on the disease. And yet with the lighting, we saw an improvement in these symptoms, which I think is pretty impressive. And obviously, we got the caregivers saying that they were calmer, they were eating better, they were easier to deal with, and all of that is they're sleeping better. So it's like, duh, it makes sense, right? It's such a simple solution.
It really is. The Alzheimer's example strikes me as a case study for something that is relevant to everybody. You're simply putting into practice the things that you described a moment ago, you know, daytime—it's so incredibly simple, right? When it's sunny—light. When it's dark—dark.
Mariana Figueiro, PhD: 15:44
That's it. Why aren't we doing it?
And then it just strikes me like, to zoom out maximally—electric lights are, what, 150 years old give or take? It's like, we're still trying to adjust to this invention that has changed our lives entirely.
Mariana Figueiro, PhD: 16:0Yes, and yet what I think is most interesting is we take it for granted. Nobody thinks about lighting in this space. Think about it. You don't look up and see what kind of lighting is up there. You don't know if it's bright or dim. You don't pay attention. You take it for granted. And yet I don't think anybody understands it. Like, to a point where they actually know how if you manipulate it, if you do it right, you can actually improve your health, improve your wellbeing, make your house prettier, if anything, wake up feeling better. I mean, right? We don't think about it.
I know you have a background in architecture. And as you're speaking, it makes me think that the light architects are sort of these magicians, that manipulate spaces that you walk into, you know, as a non-specialist, and you kind of feel different and you might not even know why or how you feel different. Do you have a favorite—we're sitting here in the middle of New York City—do you have a favorite lighted space in New York that you go, wow, this is really cool?
Mariana Figueiro, PhD: 17:13
The Guggenheim Museum. It's beautiful. It's not just the architecture, but it's the light in the space. It's just, it goes with the architecture.
Mariana Figueiro, PhD: 17:26
It blends into the architecture and yet it reinforces the architecture features of the building. That's what I think it's—and that's really what good lighting is. You don't really need to, um, you don't wanna come into the space and say, oh, it's the lighting. You wanna come into the space and feel that there's something different in that space. And if you take the lighting out, you're not gonna have that feeling. So that's the magic of being able to do that with lighting. It really—you know, lighting needs surfaces to be reflected off of so you can see. You really don't see light without surfaces. It doesn't exist in a way.
Like you never see direct light, almost never. Unless you're staring at a light bulb or looking at the sun.
Mariana Figueiro, PhD: 18:26
But even looking at the direct, what the light rays are doing is they're hitting your retina and then you're seeing it. But they're coming out of, you know, they're sort of coming out of something. But you don't have light in the vacuum.
So in terms of adjusting to this somewhat new invention, we now have screens everywhere. And I think most people listening are familiar with blue light. Is it good? Is it bad? Not supposed to look at it at night. Can you just bring some clarity to this whole mess?
Mariana Figueiro, PhD: 19:01
We definitely should not be looking at screens before we go to bed. What happens with screens is they became brighter and brighter and bigger and bigger. And the form factor—it's right in front of your eyes. So it's a very effective way to deliver that light in the back of the eye. So we've done some studies with iPads and with computer screens and with televisions, and interesting enough, the TVs, even if they're big, they're not as effective at impacting—you know, we look at melatonin levels and melatonin is a hormone you produce at night in darkness. Melatonin is not a sleeping pill, but what melatonin does is tell your body it's nighttime. And then your body sort of knows that it's time to go to sleep because that's what you do at night. So if you suppress that melatonin with light, you're fooling your body into thinking that it's not night, and that can cause disruption or it can make it harder for you to fall asleep. So by having that light—and melatonin starts rising about a couple of hours prior to your normal bedtime. So if you go to bed at 10 o'clock at night, at 8 o'clock, your melatonin starts rising in your bloodstream. So it's almost like telling you, hey, it's nighttime. It's time for you to slow down, switch off a lot of things, get ready for bed and sleep. If you are exposed to light around that time, what you're doing is you're delaying that onset of melatonin. So you're delaying your sleep. So a lot of people ask, well, what about the night shift mode? Or, you know, all these other gimmicks that people have—
Which does what? It reduces the amount of blue light?
Mariana Figueiro, PhD: 21:10
It reduces the amount of blue light.
Which is the light associated with natural light. Is that right?
Mariana Figueiro, PhD: 21:14
Which is the light that is most effective at suppressing your melatonin or at impacting your biological clock. Okay. So we're more sensitive to blue. We're almost like blue-sky detectors. So the biological clock is looking for blue light. Okay. So if you give blue light to people, you're gonna need a lot less light to have the same impact than if you give, say, yellow light or yellow-green light. You can have an impact, but you need much, much higher light levels. Okay. So what those displays are doing is they might be delaying that onset of melatonin and delaying that signal to the body. So you filter out the blue. Well, if you don't dim it down, it doesn't do the complete job. So it helps minimize the impact on your biological clock, but it doesn't completely stop the impact. Okay. Because brightness also matters. So you have to filter out blue and you have to dim it down. If you ever did that to your iPad, you can't see anything. It's hard to read. It's hard to do anything. So turn it off. That's the best thing
You're saying if you really dim it down as much as you should, it's not a usable device.
Mariana Figueiro, PhD: 22:42
It's not usable because you can't see anything. So if you do it for 15-20 minutes, okay. You can read on your iPad, for example, reverse polarity. So do the, you know, black background with the white font because that black background is not emitting as much light, so it makes it less bright. So you know, a lot of people like to sleep or reading makes them sleep. So, okay, you can do that, but just reverse the polarity and minimize the amount of light. So there are ways that you can do it. Just—there's no need to be on your iPad before you go to bed for 2, 3, 4 hours.
So I'm sort of keeping a log in my head, right? These are the changes that I'm gonna make. So I've got the first thing in the morning, blinds open, try to get natural light, maybe go for a walk first thing in the morning. During the day, try to get out, again, go for a walk, as much natural light as I can.
Mariana Figueiro, PhD: 23:38
Have your lunch outside, you know, go out.
Are there any other sort of low-hanging fruits that you recommend to people that they can bake into their every day without having to think about it every time.
Mariana Figueiro, PhD: 23:49
Regularity. You know, we joke that a healthy life is a boring life. It's interesting, I know that's very hard in New York City, for example. And I know because I come from upstate, right? I come from a very small city—Troy, New York, which, you know, you talk about boring. It was boring. And you come to New York and you have so much more to do. And what happens is you're not as regular. I'm not as regular as I was. I don't go to bed at the same time every day. I don't wake up at the same time every day. Maybe I go to dinner and one day I get home at 11. The other day I get home at eight. That didn't happen before. So maintaining that regularity in what you do seems to be very important for the brain and for the body. And the regularity means you're also regular in when you're getting the light and when you're not getting light. Because remember when you fall asleep, when you close your eyes, you're shutting off all the lights from getting into your eyes. Your eyelids have very, very poor transmittance, especially the blue light. So you need a heck of a lot of blue light to go through your eyelids, to disrupt your biological clock. So closing your eyes means you're in darkness, and opening up your eyes and opening up the shades in the morning means you are in, you know, bright days or brightness. And that's what you want, and you want that day in and day out.
Is light pollution a big problem?
Mariana Figueiro, PhD: 25:41
It can be. But it's interesting. There's a lot of argument about that. There are some hypotheses, or there are some studies actually that they look at satellite images and they look at spaces where you have, you know, those very famous images where you see New York is this horrible amount of light and then in the middle of the country, there is nothing. And you know, you look at the world and so on. And what they do is they look at these satellite images and they correlate that with diseases like breast cancer and so on. And what they claim is spaces where you have the highest brightness in the satellite are spaces where you have more incidents of cancer. I think there's caveats that we need to think about with that. And the caveat is that that doesn't mean you're getting that much more light indoors. Okay. Because what we do as humans is we tend to have shades, blackout shades, we tend to block that light pollution from coming into the space. But what I think light does and the light pollution is a surrogate for that, is it's an enabler. So what it does is enable you to disrupt yourself. So yes, New York City, there's much more light pollution than Troy, New York. And of course, New York City, you have a lot more stuff to do to disrupt yourself than you have in Troy, New York, for example. So I think it's an indirect impact. So in other words, even if I don't get more light in my bedroom because there's more light in the sky, what that light in the sky's telling me is that this is a more lively city or space and I'm gonna have more opportunities to disrupt myself.
I wanted to ask you about shift workers. Because I'm sure there's somebody listening to this who, you know, has to stay up through the night in bright lights and, you know, it's not an ideal situation. So what can somebody do in that case to kind of mitigate the maleffects of that lighting scenario?
Mariana Figueiro, PhD: 28:07
I have to say I have the greatest respect for shift workers. It's a very, very tough profession. I mean, you're staying awake at night, fighting your biological clock, which is telling you to sleep day in and day out. I mean, it's really hard, and that is one of the hardest professions. And even it's one of the hardest applications to find solutions. Okay. So we've been working and trying to study ways of minimizing that. First of all, I think it's very interesting. If the nurses have controls over the lights at night, they will naturally dim it down. I've worked in newborn intensive care units and ICUs, and at nine o'clock these nurses would just bring the lights down. It was just their instinct to. Now obviously by doing that there's the negative side that you're gonna be sleepy. It's gonna be harder for you to fight your urge to sleep. So there's a safety issue that we all need obviously to worry about because we all want perky nurses and physicians at 4:00 a.m. in the emergency room. So we've been working with the possibility of using red light, and what red light does, it's interesting enough, it's almost like it's an alerting stimulus. It's impacting your flight-and-fight system. So think about, you know, red seems to have that notion of danger and, you know, for whatever reason it activates the brain. People are more alert with the red. And yet the red doesn't impact melatonin levels. And it doesn't impact your biological clock because your biological clock is pretty much blind to red light. So we've been working on trying to implement things like that. Now this is obviously still on the research side. The question is what about a person right now on their shift, what can they do? You know, on their shift it's very hard. My tendency is to stay on the low-light levels and try to stand up, walk, drink coffee, do things that will maintain your alertness. But more importantly, when you go home, if you do public transportation, for example, try to minimize the amount of light you get in the morning. Believe it or not, for shift workers, you wanna minimize that morning, because that will delay their sleep when they get home. So if they remain in dim light or if they avoid outdoor light on the commute home, that will help them fall asleep faster when they get home. Get the shades down, have blackout shades in your room, sleep in the darkest room you can. And, you know, there isn't really an easy solution for this population. And that's why I respect them so much because it is really hard.
Something you said about color—I'm looking, I can see through this window a reflection of an exit sign and I'm seeing the red exit sign. And what you said about red light and how the brain responds to red with alertness, but not melatonin, it just kind of sent my imagination careening into different places about how we may be hardwired to respond in certain ways to certain colors.
Mariana Figueiro, PhD: 31:48
Yeah, we may be. You know it's interesting, the research on color is—it can go from very good to very bad. You know, there are some kind of weird studies about color perception. So I think a lot of people don't take it very seriously, the impact that color may have on us. I think a lot of it comes from the perceptual system in a way, from how you feel about colors, but that "how you feel" can lead to physiological changes. So I think, you know, it's interesting because I never really studied the "how you feel" part about colors, because I always thought, eh, it's all like, you know, bogus and so on. But then when we did this study where we were measuring EEGs, which is brain activities, and we saw this very strong response to the red light, I started trying to understand, so why is it that we're having that strong response? And then you go back into the literature and you start, you know, there were some studies where, for example, sports games, if the opposite team was wearing red jerseys, they tend to win. Because people were intimidated or afraid or there was a reaction about it. They claim that there's a reason why you go on a date, you have red dress and red lipstick, it's because it's associated with attraction. They've done studies with grips, for example, that if you have something that they ask you to, to, you know, the grip and if the handle is red, that people actually grip more or it's a stronger grip. So it's like why? And then you have the things about fire and danger and, you know, so I think that it's the fact that the brain associates with something and then that association will lead to a response.
It sounds hardwired. I mean, is there any suggestion that the effect is refracted through culture?
Mariana Figueiro, PhD: 34:20
There could be. And especially like you think of China and other countries like that that red is a very strong color. I have not looked at different cultures and different groups of people. I haven't looked at it, but it could be, it definitely could be. I mean, you even think about socio-economic status. I mean, it may be that if you're born and raised with flashing lights, you know, of police cars and you see that you may have a strong reaction to that kind of light.
The portrait that you seem to paint of light in general and the importance of light, it sounds as though you're advocating for light to be elevated to the level of the quality of the air we breathe, the quality of the food we eat, the quality of the materials that we surround ourselves with. Do you feel like that's the status that light should have?
Mariana Figueiro, PhD: 35:26
Absolutely. I mean, I have no question about it. And I think that unfortunately—I use the example of ergonomic chairs. You wouldn't think of having an office without ergonomic chairs anymore, right. And you will pay more for ergonomic chairs, but you gotta do it. It's just, you can't give crappy chairs to your office workers or your healthcare workers anymore. And I think lighting has to be the same thing. You just can't do it. Because the impact on people is so profound that you just, you shouldn't take it for granted. So absolutely. And you know, if I can do that, I can retire. That's my goal. So, you know, some people may say, oh, we don't want it to happen because we don't want you to retire. I'm like, eh, well eventually I will. So I hope I can retire with something elevating lighting a little bit. I think it's a great way to put it.
Well, I hope, you know, us having this conversation does a little tiny, tiny, tiny, tiny piece of spreading that awareness.
Mariana Figueiro, PhD: 36:45
Yes and I think it has. I tell you, I've been at Mount Sinai for a little bit over a year and I'm very impressed with how people are really interested. I mean, you know, I told you that I thought that people were gonna say, light, what, are you kidding me? And no, I think everybody's actually very well receptive and trying to understand. When I'm working with a group, working with Parkinson's disease, and I mean, everybody's excited, they're genuinely excited about it. So, yeah, the more we talk about it, the better it is I think. It's just, we gotta spread the word. So thank you.
Thank you so much. It's been so nice talking to you.
Mariana Figueiro, PhD: 37:34
Yeah. it has been. Thanks very much.
Dr. Mariana Figueiro is Director of the Light and Health Research Center at Mount Sinai. This interview was recorded at the Levy Library at the Icahn School of Medicine at Mount Sinai. Road to Resilience is a production of the Mount Sinai Health System. It's made by me, Jon Earle, Nicci Cheatham, Emma Stoneham, and our executive producer, Lucia Lee. From all of us here, thanks for listening, and we'll see you next time.