Dr. Jamie Zeitzer. Expert on circadian biology in sleep. Ba biology at Vasser College. Phd in neurobiology at Harvard University, and was a fellow post doctoral


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NameDr. Jamie Zeitzer. Expert on circadian biology in sleep. Ba biology at Vasser College. Phd in neurobiology at Harvard University, and was a fellow post doctoral
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Dr. Jamie Zeitzer. Expert on circadian biology in sleep. BA biology at Vasser College. Phd in neurobiology at Harvard University, and was a fellow post doctoral fellow at UCLA and Stanford. Currently is an assistant professor at Stanford. The reason I wanted to talk to him today is he is an expert and has published a lot of research on a lot of topics I’m interested in in sleep, circadian biology, vagus nerve, and SNPs that are of interest. I’m actually not sure if he is into health at all, this is mainly, trying to get the science of what is the most recent science on these topics. So I’m really excited to have him here today.
Q: Topic of interest is lighting at night. What amount of lighting at night will phase shift a circadian rhythm, or affect people’s melatonin production or negatively impact their sleep?
A: Not as straight forward an answer. There are two aspects. 1 is how much light can affect you, and the other is how much light does affect you. If he brings someone into a laboratory and keeps them in dim lighting for most of the day, he can then show that really dim light at night can have an impact. He usually measures things on terms of the lux unit. 5-10 lux would be really dim lighting.
Q: Like what? People are in cities and they think well they’ve turned off their lights, but there are usually light bombs coming in from outside. Is that enough? What is that, 5-10 lux?
A: Usually it is. If you can still see color, you’re usually at least above a lux.
Q: What about things like, I have a charger that emits blue light, various appliances that emit blue/green light. What will that be 10-20 lux?
A: Those are going to be pretty dim. If you’re watching television at night and the lights are out in the room, and you’re sitting 5-10 feet from the T.V, that’s going to be 5-10 lux or so, seems bright because of the contrast, but it’s not that bright. It has a nominal effect. When you get into room lighting, you see much more substatial effects. The problem with this is much of this is mitigated by daytime light exposure. If you spend much of the day indoors in a dimly lit room, then these lights will have more of an impact. For example if you’re spending much of the day in a dimly lit room and use an iPad at night, then that’s going to have a stronger impact. But if you get out it’s going to have a much lower impact on your system.
Q: Let’s say someone is getting bright light in the day, what should they stay away from at night time?
A: If they’re getting bright light during the day, then during the time that you want to be asleep, you want to avoid anything brighter than normal room light. If you have a 50W bulb, something like that would give adequate lite to read, watch TV, use the computer, that amount of lighting won’t have that much of an impact. One of the keys with the lighting is “what are you doing with the light?” The thing that keeps people up, kind of shooting my own work in the foot here, in the sense that I spent years describing how light impacts the system, but in terms of how it’s affecting sleep, you also have to focus on what the person is doing with that light. If you’re up and you’re checking your email before you’re going to bed, and it’s stressing you out, that’s going to do a lot more harm than the light is, in terms of affecting your sleep.
Q: Is that because stress hormones like CRH or an overactive nervous system in general is going to cause a phase shift for your circadian rhythm?
A: Well it’s not going to cause a phase shift, but it will cause an acute increase in alertness and anxiety and these things will make it more difficult to fall asleep. In the sleep area it’s a very person-dependent thing. For example, some people have difficulty falling asleep because they have a difficult time with all the stresses of the next day. So for some people it’s helpful to write a list of all the things they have to do the next day. In some it works very well so they aren’t cycling through the to-do list in their head. In other people it’s terrible because it just reminds them of all the things they have to do the next day. Really depends on the person and their personality.
Q: So what’s your personal approach for lighting at night, with you and your family, if you were to implement something for optimal health. What would you do and what do you do, two different questions, because your family may not be on board with some things.
A: He’s a firm believer in getting the good amount of darkness at night. When you wake up in the middle of the night, having a dark environment is conducive to sleep. In his kids rooms they’ve installed blackout shades, youngest is sleeping in a room with no windows. It’s a limitation because where they live they don’t have a lot of space, but now he isn’t aroused by certain sounds around the house. For much of sleep it’s about establishing good patterns. If part of the pattern is going to sleep in a dark quiet room, then that’s a good thing.
Q: Ok, and when do we want to turn off the lights? There was a recent study about what hunter gathers in certain parts of places close to the equator were doing, I’m sure you read that, and they did find that before they went to sleep there was 4 hours of darkness, and I find personally, and other people, there’s maybe some anecdotal support, and we see even a small amount of light 5 lux, which is less than just turning on a light, it’s even what you can get outside, and we see that a lot of peoiple are doing better. I’ve done a lot better, the more light I cut out the better I’m able to fall asleep. So what do you think that’s about? So your recommendation is that ok it’s fine as long as you don’t have it brighter than a room light or something and right before you to to bed, is that what you’re recommending?
A: So again, it’s a very interpersonal thing. Basically people have to find a balance. The light is going to be alerting, and that’s negative, in terms of falling asleep. But the light is for what purpose. So for example he likes doing cross word puzzles before I fall asleep. It relaxes him. There’s a certain amount of light required to do that which will be somewhat alerting, but for him, the relaxing effect of the crossword puzzle for him outweighs the small alerting effect that he gets from the light. It’s a real balance that people have to strike. For example, for people with insomnia, who get up in the night, they technically should avoid light, because that’s going to make them even more awake. However, if just sitting in darkness makes them anxious and their sleep worse, perhaps they should turn on a light and read and that can help them. So there’s no real absolute.
Q: It seems like you’re approaching it in terms of alertness vs non alertness and overall alert system, vs. before we spoke I thought of it, before we spoke, more of it as like the light is activating your superchismatic nucleus and that’s shifting your circadian rhythm or it’s changing it in some subtle ways that we may not even be able to fully appreciate at this point just because it’s such a complex system. Do you think there’s anything to that, or is it mainly how alert are you and how relaxed you feel?
A: So light is going to have multiple effects. In addition to the obvious seeing images aspect of light, light does lots of other things, shifting circadian rhythms, increasing alertness acutely, change the hormonal release, purple dialation, and there’s probably other things we aren’t even aware of, there’s pretty good evidence that it’s linked to changes in mood. these are all things light can do. In terms of it’s impact on when you sleep, the lighting that you’re getting at night I think is going to have an acute effect, increasing the alertness, as well as the long term effect, which is going to be establishing a different circadian time. Therefore on subsequent days, making it easier to stay up later. There’s kind of a combination there. So if you normally stay up until 11, and now you’re staying up in a well lit room until 1am, that extra 2 hours, the light that you’re getting there is going to help you stay up because of alertness, and it’s going to also shift your rhythm or at least contributing to a shift in your rhythm so that the next day it will be easier to stay up until 1am.
Q: I’m curious what your take is about this. There’s a doctor that claims just the amount of blue light that we’re getting is harmful. He claims that it causes photooxidation of DHA and it causes an increase in ubiquination. Do you have anything to say about those things?
A: There’s definitely evidence that excess of blue light is not good for the retina. How much of that is applicable at a real physiologic level is the unknown. So it has the capacity to do that kind of damage. Whether the standard amount of blue light that you’re getting off electronics, is that enough to do that kind of damage? That’s really unknown. Usually what happens in these studies is you extrapolate from high intensity short term exposures to low intensity long term exposures. That’s not necessarily a proper equation. That’s not to say that it is or isn’t damaging, it’s just that we don’t know.
Q: Do you personally have a program like F.lux to reduce the amount of blue light you’re getting through screens?
A: I don’t. I know a lot of people like it, and if/when it helps people it’s great. I don’t use it because I don’t use computers at night, not because I’m worried about the light, but because of the cognitive activation that might occur from that.
Q: What about something like bright light sensitivity, now that we’re talking about blue light having the capacity to damage the retina. Some people are more sensitive to bright light, and probably from the blue spectrum. What is the bright light sensitivity from.
A: We don’t know, or at least I don’t know. I know that definitely people have sensitivities to that. Sometimes i’ts more of a central process because their hypersensitive to lots of different modalities. So they’re not only sensitive to light, but their also sensitive to sound, touch, smell, and that’s more central. But we don’t know why some people have that. There are also people who are super tasters. There are some people who have extra cones and have a greater ability to discriminate color. So there are various biological explanations, but for that one I don’t think we have a direct explanation.
Q: What are the percentage of genes, directly and indirectly, controlled by the circadian rhythm? I know there’s no firm answer, but what does the research say, and what do you think as more of a liberal take on it?
A: The current research says 15-20% or so, I have a feeling that number is drastically incorrect. I have a feeling that number is closer to 90%. The reason basically is that the circadian clock temporally organizes everything. It’s a master clock that controls clocks found in basically every tissue of the body, and it helps to anticipate changes. The question is it takes energy to transcribe genes and make them into proteins. If you don’t need that or there’s no reasonable expectation that you are going to need a certain process, then there’s no reason to be transcribing that gene. You can think of it in the most simple approach in a plant. A plant at night has no reason to have photosynthetic machinery running at night, so why bother? If you look at plants you look at how the genes are transcribed, things involved in photosynthesis aren’t being transcribed at night. You can think of this in the very same way in humans. If you’re going to optimize energy utilization, which I think many of our cells do, you don’t need to have everything active at all times. in fact the interesting genes are those that need to be acitvely transcribed all day because these are the ones that are necessary for the cell just to function. Many of the events that are going on in the day are different than the ones that are occurring at night. So it makes sense that there is going to be some sort of anticipatory regulation of that at the basis of the circadian clock.
Q: That’s really interesting. So somebody like you realizes the importance of the circadian clock, instrumental to almost everything in the body, and we know that a tiny bit of blue light can really disturb things. And we know we’re getting more light at night even if we try to block it out, than we’ve ever gotten. I believe the moon is 1 lux, what one researcher told me?
A: Yes, a full moon on a cloudless night you might get a lux.
Q: Wow so that’s even rare. So we’ve been exposed to maximum 1 lux and it seems like we’re getting way more. It seems like such an important thing I try to take as many measures as I can. I wear red glasses at night to try to block out as much light. Because I do use computers at night. Mainly blue but secondarily green can disrupt the circadian clock and play with melatonin and the superchaismatic nucleus, it seems like such a delicate system.I try to take the most precautions, especially for someone like me who’s had issues with insomnia in the past. What’s your commentary on that?
A: When looking at the spectral sensitivity, as you mention there’s a blue, we are more sensitive to blue than other spectrums of light, in terms of the circadian system. When we look at visual perception or image perception, we’re optimally perceptive to green light. So if you need to function and do things at night, than say exposure to an orange light, is going to be optimal in a sense that you’re still going to have good acuity, and going to minimize the effects on the circadian clock. Now we don’t know again what the long-term consequences of this behavior is. As you mention evolutionarily what we’re doing now has never been done before. The past couple hundred years of electric lighting, we’ve exposed ourselves to far more light at night than humanity had ever, in the millions of evolution proceeded. But we don’t know what the consequences are.
Q: So I guess it’s just a matter of 1, if you’re having insomnia, you want to try blocking out more light, especially the blue spectrum. I guess how precautionary someone is to the unknown.
A: As you point out, a lot of this is you have to compare who you are as a person, personality, basic biology and traits with the counter measures. for example, if you sleep fine, you don’t need to do any of this stuff.
Q: It’s still possible there’s some effects or a variety effects on the circadian clock. If you have a night shift job, you might sleep fine, but the fact is you’re at risk for a whole risk of diseases, right?
A: Correct. The better you sleep I think the lower your risk is.
Q: Oh I see.
A: Again, there are a lot of stories, basically a lot of older people come in. They’re not sleeping. So you talk to them and you find out well they slept fine for the previous 75 years of their life they slept fine, now they don’t. You talk to them, and find out every night after dinner they have a cup of coffee. Well, perhaps that’s doing something. Perhaps it’s not good to have 300 ml of caffeine right before they are trying to go to sleep. And they say it’s never been a problem before. And that’s true. Because their sleep was good enough that they could have a big dose of caffeine before sleep and it didn’t impact their sleep.
Q: That’s the problem though. How do you know it’s affecting their sleep? You’r not putting yourself through an EEG machine, through the mo dern technology testing. Subjectively yes I think I got a good night’s sleep I’m not sure.
A: It’s kind of funny we actually just submitted a paper, you can’t find it yet but hopefully soon, where what we did was we took a look at the gold standard sleep recording which is polysynography, where you hook electrodes to someone’s head, and you monitor all of this electrical activity in their brain during sleep, and this is the gold standard for clinical sleep studies. We looked at this in 1500 older men and women. In the morning after they had one of these sleep studies asking about their sleep quality, asking how was their quality of sleep. So that was the questions that were asking. Well we did all sorts of fancy statistical modeling techniques with this, the latest and greatest, and basically found that the polysynography has very little to do with how you answer that question. About 15% of the variability was explained, which basically means is that what we’re recording in the gold standard of recording sleep and the current things that we can derive from that, actually explained very little about the answer to the question of how did you sleep last night. And so there is a split, this question of how is your sleep, it is a very dependent on the actual more precise question that you’re asking. So is it sleep quality from a subjective perspective, which is one thing, and you can get 8 hours sleep quality. There’s also the sleep quality from the functions of sleep. So for example was there good consolidation of memory during sleep. Did you have proper reorginization of various metabolites in the brain during sleep? And these are the questions we are only starting to address in the field. So for example if you sleep for 3 hours, is that sufficient for memory processes. We don’t know.
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