Catch Some Zzz’s: The Cognitive Benefits of Quality Sleep

Intro: I’m Dr. Nathaniel Chin, and you’re listening to Dementia Matters, a podcast about Alzheimer's disease. Dementia Matters is a production of the Wisconsin Alzheimer's Disease Research Center. Our goal is to educate listeners on the latest news in Alzheimer's disease research and caregiver strategies. Thanks for joining us.

Dr. Nathaniel Chin: Welcome back to Dementia Matters. Today, I'm joined by Dr. Allison Reiss, an internal medicine physician and molecular biologist who studies the causes and treatment of Alzheimer's disease and other forms of cognitive impairment. She is head of the Inflammation Laboratory and Associate Professor of Medicine at New York University's Grossman Long Island School of Medicine. Dr. Reiss is also a member of the Medical, Scientific and Memory Screening Advisory Board of the Alzheimer's Foundation of America, where I also serve and have had the pleasure of getting to know her. Allison, thank you for joining me on Dementia Matters.

Dr. Allison Reiss: Thanks for having me. It's just a delight to be able to talk to you as we've gotten to know each other. I know how dedicated you are to helping people with Alzheimer's disease and their families, as am I. It's great to be able to combine forces today.

Chin: Well, this episode is a bit different from my usual interviews. I've asked Allison to be here so she and I can discuss sleep and its relationship to our health, particularly brain health. Neither one of us are sleep experts, but Dr. Reiss and I are both internal medicine physicians and we're passionate about understanding sleep. In this episode, Allison and I will ask each other questions about sleep and its impact on the brain. If you'd like more information about sleep, I recommend checking out Dr. Steve Barczi's podcast episode from November 21st, 2017, which will be available in the show notes. To begin, Allison, how do you see the connection between sleep and health?

Reiss: Well, it's very clear that good sleep contributes to overall health and quality of life and that we benefit in body and mind in multiple ways from sound, refreshing sleep. I think we all know that and experience that in our lives every day—how our whole day goes better, and we feel more able to just cope with everything that we have to handle when we get a good night of rest. As we age, many of us have more difficulty either falling asleep or staying asleep. There's a lot we can do to counter this. Nate, why do you think sleep is so important?

Chin: I agree with everything you said, and I also think about sleep from this brain health, lifestyle habit perspective, as I'm very interested in modifiable risk factors for cognitive change. I look at sleep as this keystone habit. What I mean by that is a keystone habit is one that has a big impact on other areas of your life, often triggering a domino effect so that other habits become easier and more manageable. I believe that multiple habits are better than one habit, and one habit is still better than no habits. To me, sleep is foundational in impacting how we feel, our mood, our motivation and our energy level. I think all of us know this—every time we have a bad night's sleep or a few bad nights' sleep in a row, sleep recharges us. When it's done right, it does set us up for a good day, but when it's done poorly, it does limit what we can accomplish. If you aren't sleeping well, I can't imagine you're gonna be willing to exercise, eat well, manage stress, spend time and enjoy time with other people, stimulate your brain beyond what is required and make these healthy choices. I know personally when I don't sleep well, I do eat things that I normally wouldn't eat and I certainly am not as pleasant of a person around those I care about. I recognize that sleep is just this really pivotal habit, and it has, of course, a connection to our health. While I want my patients to do all these things—all the brain health habits and more—I recognize that if their sleep is poor, they may struggle, and not because they don't care or believe the things that we know are important, but because it just is hard to do that when we're so tired.

Reiss: I think that really sums up a lot of what we see in our real lives. Do you think that scientists are recognizing the importance of the link between sleep and brain function? Are they studying this issue?

Chin: Yes, yes. Fortunately, I did a quick search on the website clinicaltrials.gov before you and I were talking, and I was looking specifically at sleep and cognition or dementia. What came up were over a hundred studies listed—some had already been completed, others were still recruiting and some are just ongoing. I found studies looking at sleep with exercise, which happens to be very popular, sleep with cognitive behavioral therapy for insomnia, obstructive sleep apnea and cognition, sleep and circadian rhythms—which I know you, in particular, know a lot about and I'll ask about later—and then some looking at interventions on sleep that have had outcomes related to cognition. Cognition could be certainly a part of a study, or it could be the thing that we are looking at. Now, other studies, like the one that I'm a part of—the Wisconsin Registry for Alzheimer's Prevention, known as WRAP—we are looking at sleep as a variable as we are trying to understand how people are getting older and what factors might relate to aging as well as disease. We follow individuals over time and then look at sleep, as well as other factors like mood, social stressors and cognitive enrichment. Now, WRAP—if you don't mind, Allison, I'll just tell you a little bit about WRAP—it is one of the world's largest and longest-running studies of people at risk for Alzheimer's. It started in 2001, and we have unbelievably dedicated participants that come in every other year, and they go through hours of a process with us where we are collecting their history—things like sleep in particular—but then also doing cognitive testing for over a couple of hours, physical exams, blood work, imaging scans—some of which are research and not done in clinic—lumbar punctures. Then we say thank you. Later on, we do end up talking to them about some of the things we found. We're trying to return more of these results to them, but it is an important way for us to understand longitudinally what factors from midlife and later adult life could impact a person's thinking ability, as well as some of the biology of Alzheimer's disease. There's this recent study that really comes to mind, and it was investigating the impact of sleep in 619 healthy participants. It was done by a researcher, Dr. LianLian Du. She showed in this study that those that were poor sleepers—and these are all healthy people—but they filled out sleep surveys, and she was able to break them into groups of poor sleepers, okay sleepers and good sleepers. The poor sleepers had this relationship or an association with worse cognitive performance, meaning they did these thinking tests with us and they had lower scores, but it was in areas of learning, memory and executive function. For those listening that aren't familiar with that term, executive function is the ability to multitask, to plan, to organize, to reason, to problem-solve. It's a really important function of the brain, of course. She also found a relationship, though, between poor sleep and people having higher body mass indexes—the BMI—having a higher waist-to-hip ratio, meaning they're having more fat or at least size around their abdomen, and then greater insulin resistance. Insulin resistance, of course, being one of the mechanisms leading to diabetes. The study did not find a relationship between poor sleep and the development of this amyloid protein—one of the proteins we are using to define Alzheimer's disease. It was a really important study, and I think it's really not the beginning, but in the midst of the scientific field trying to understand what exactly the role is of sleep in our thinking ability, our metabolic health, and certainly, as we have more biomarkers, in the biological processes of getting older and having disease. Now, despite our study not seeing this relationship between poor sleep and that protein of amyloid, there is data to suggest that amyloid protein is cleared from the brain during sleep via what's called a glymphatic system or pathway. Allison, can you share for our listeners, what exactly is this glymphatic system?

Reiss: Yeah, I'm happy to do that. I just want to say that the WRAP study sounds excellent. The way it's conducted really should yield a lot of important data. I think that more and more we're going to see that there are issues involving the brain other than amyloid that need our attention when we are evaluating that relationship to cognition and dementia. Getting back to the glymphatic system itself, the brain is bathed in fluid at all times, and that fluid is carried through the glymphatic system. It's a network of channels or pathways within the brain that helps deliver nutrients and remove waste products. It's similar to the body's lymphatic system. Our way into the glymphatic system, in which we can get a real look at what's happening in living people, is through our spinal fluid, where we can remove some of that in a spinal tap. It was discovered that the glymphatic system is mostly not very active during wakefulness, but it gets very active during natural sleep, particularly during the deepest stage, stage three. Studies have shown impaired glymphatic clearance being associated with neurodegenerative conditions like Alzheimer's disease. Also, there's a less efficient functioning of that system with aging. We're starting to see some clues about how important this system is, and there's a lot of active investigation on it. I think there's so much that needs to be understood about how this system relates to other measures beyond amyloid, like looking at inflammation or mitochondrial powerhouses that give cells energy and overall bioenergetics. There's a lot more to come from that glymphatic system.

Chin: Allison, one of the interesting things you just said to me was that science right now is showing that it's active during stage three sleep. As a non-sleep expert, I recognize that that's deep sleep. That's the sleep that happens later in a person's sleep cycle. To me, as we talk about sleep health and sleep itself, it does tell me that if this is an important process, then it's important that we as people get into that deep sleep because sleep can be interrupted—and I say that as someone who has two young kids and it's often interrupted—it does emphasize this importance. It's not just, and I know we'll talk about this in a minute, but it's not just the quantity of sleep that you get, but that you are able to actually complete all of the sleep stages and that you're able to get into this deep sleep. It does seem like each stage has its role and its importance. One of the important roles for stage three is that it clears out these proteins. Like you said, other factors are probably happening, or other mechanisms that matter, that we still just have to study.

Reiss: I think that's so true. We have so much to learn, and going through the whole process in the orderly way of the stages of sleep is very important. Like you say, often we can't do it. I remember having young children—my kids are all grown now—but the same thing, getting that sleep was a big challenge. There's no choice, you get through it. Now, given what you found in the WRAP study and your belief about the value of quality sleep, what are your general recommendations to patients who ask about sleep or sleep hygiene?

Chin: Yeah, that's a great question. I do enjoy talking about sleep to my patients and out in the community. I think I start with asking people, "Well, what do you think is wrong with your sleep?" Because I think people are really insightful. They might not think about it in the moment or, frankly, they're too tired or busy to think about it during the day. When you ask them, "When you think about getting more sleep or getting better quality sleep, what do you think are the barriers for you?" you'd be surprised how many people, right at the tip of their tongue, are able to tell you. "Well, I watch TV right until bed and then I can't fall asleep," or "I'm doing a lot of work right up until bed," or "I have that extra cup of coffee," or "I drink more alcohol later in the evening." They know some of the things. I think it's inherent to us to recognize that sleep is important and that there are certain ways we can help our sleep, but that we tend to not live the life or make the choices that always work that way. I start with getting a sense of, "What do you think?" and then move on to talking about quantity and quality. I think both of those things are going to matter. In general, people say seven to nine hours of sleep is important. There are studies that show less than six hours of sleep is not good for us and that more than 10 actually may be a risk factor for later developing thinking changes. It isn't just that less is bad—even having too much could potentially be a problem. Then I like to talk about sleep routines, because I think these sleep factors lead to sleep and, certainly, how we live our life during the day can impact how we're sleeping at night. We'll get into that in a few minutes, but sleep hygiene, I do think, is a foundational approach for people who are struggling with sleep. Most people will say, "Oh, I know all those things," but there’s a lot. There’s some really great resources out there. There are a lot of different things that we can address. I doubt all of us are doing everything perfectly, so there's always still something for us to consider. Then I'll move on to quality, because in addition to quantity, how well we sleep matters. I think the key things are not having a lot of interruptions because of this idea of getting into that deep sleep. Feeling refreshed in the morning is a good indicator of whether or not you really did sleep okay despite being in bed for eight hours or more. Then I'll talk about what factors can actually interrupt our sleep. Commonly, as people get older, it's called nocturia—this idea of going to the bathroom. You just aren't able to hold your bladder as well as when you were younger. There are certain factors, of course, that contribute to this, and this is where I'll talk to people about not drinking so many fluids right before bed and not drinking alcohol after a certain period because that can lead to a person going to the bathroom. Pain is another factor. As we get older, we might have more muscle or joint pain, so is that the factor for you? Should we be treating that? I know, Allison, I'll ask you a question about this a little bit later. Racing thoughts, anxiety and rumination—these are factors I hear a lot about in my patients. Worrying about the world, their family, their job—once they're up, those thoughts just keep coming. Then the last one I'll mention is one that affected me, which is having the dog on the bed. We love our pets, or some of us do, and you want that pet close, but they're not ideally supposed to be there. They can move around too, and that could disrupt you. What is your sleep environment like? That's another factor I'll talk about. The sleep environment matters—you want it to be cool. I read an article once that said ideal temperatures are really cold, like 62 to 66 degrees, which is really cold. You want the room to be dark, and if you need to have a sound machine or something that makes noise, some people really like the weight of a blanket, even in the summer. Are you able to have an environment where you feel that comfort? Lastly, I think you, as an internal medicine physician, would do the same thing: just address, are there medications you're taking that could be impacting sleep? Are they stimulating? Are you taking in substances that could be impacting sleep—not just alcohol, but even things like coffee in the afternoon or certain teas? There are a lot of things that we could ingest that could be stimulating. If we simply took them earlier in the day or stopped taking them, I think people might sleep better. That's sort of my general approach. I usually can't get through all of it in one sitting, but I think identifying some of these factors can be really helpful to people and certainly connecting them to the resources. Are there other things that I have missed, Allison, that you tend to recommend to people who ask you about sleep?

Reiss: Well, I think that you really hit all of the important points, and especially some of the things like kind of the sweet spot of those seven to nine hours—like not too much or not too little. The problem of those racing thoughts—I think that is so common. Also, I would point out, just for people who are kind of in bed and thinking and they get into that spiral, sometimes for me, my greatest creative ideas come in the middle of the night when I'm lying there and thinking. Don't discount that some of what you're thinking can actually be productive. Your brain is kind of in a quieter place, and it gets to really kind of meditate and think about a lot of things. The issue of the nighttime—having to urinate and having to go to the bathroom and be disrupted—that's a tough one because when people don't drink enough fluid, especially older people, they have the danger of being dehydrated, which really can land people in the hospital and make them more confused. Also, they can be more likely to get urinary infections, which, again, are pretty tough. You have to balance—you know, is it worth it to get up in the night and not end up dehydrated? We all have to grapple with all these things. Nate, for those with chronic insomnia that know all the different sleep hygiene factors, what else is available for them?

Chin: Well, I think you brought up a really good point, Allison, when you mentioned perhaps some of your nighttime thoughts are gonna be really productive later on. I mention that because whether it's a productive thought or rumination, sometimes it's helpful to actually write it out. Sleep journals can be used for many different things. You could write it just simply so you can observe—well, how am I actually doing? Like, when am I going to bed? When am I waking? Am I waking up in the middle of the night? It could just be a record-keeping tool, but it could also be a tool for what I would consider to be partly cognitive behavioral therapy. We're actually putting your thoughts into this sleep journal because they are keeping you up. If you're ruminating on a list of things you have to accomplish the next day, well, put it into the journal and recognize you're not going to lose it. You're not going to forget it. It's there. That can actually be reassuring to people so they can move on from the things they are ruminating on. Of course, in your case, perhaps it's a brilliant idea of a study that's going to happen in the next year—it could be productive too. I think the sleep journal is helpful. I know it's a hassle for many people, but I do think it can be foundational in understanding what's happening. I think, as a clinician, of course, reviewing medications—including supplements, including any substances—your primary care provider would be perfect for that. If needed, seeing a sleep specialist, a sleep medicine provider—they can evaluate for many things, not just sleep apnea. Though sleep apnea is important, but restless leg syndrome, periodic limb movement disorder—there's a lot of different conditions that people might have that are undiagnosed. I will go back to the sleep apnea thing because I do think that's a major issue, and it's more common than people think. A CPAP machine, which is one that provides air that keeps your airways open, has been shown in those that need it to improve cognitive function and health factors—our mood, our levels of energy. Our blood pressure can be traced for some individuals to untreated sleep apnea. There's a great benefit to that treatment. People are usually resistant in the beginning, and now I have patients that have a separate CPAP just so they can travel with it because they know how important it is, and they feel so good with that treatment. I'm not gonna be prescriptive in this episode and I'm not gonna use any drug names in particular, but there are supplements that people can take, and these are over the counter, so I don't mind mentioning at least some of the names. Some of my patients will talk to me about melatonin, and we'll talk about that in a second with circadian rhythm. Valerian root is a common supplement people come to me with, or even teas, like chamomile tea, can be something that a person could consider. For the prescription medications, you could adjust the timing. Again, I would talk to my primary care provider about this, but you could adjust the timing that you take medications. There are medications that people might take for their mood, which is often related to insomnia. Some of these medications actually have this benefit of helping with sleep, but there are some I would also avoid too. Some of the sedatives that people will commonly take for sleep are actually not helping you get into the deep sleep. They're just sort of sedating you and causing you to not be awake, so I would be careful about those. If you're on one of those, talk to your doctor—particularly a sleep doctor if you have one—about that. When we get to that extra level where sleep hygiene is not doing everything, what else can I do? That's sort of the run-through of what I recommend for my patients and people I talk to in the community.

Reiss: That sounds like a lot of good, solid, practical information. I totally agree with you about avoiding the unnatural sleep that comes with medication. I mean, there's nothing really like unnatural falling asleep. What we don't want you to do is take all these things and then worry and stress about sleeping and how this might impact your ability to sleep. Just keep in mind, if you are lying in a comfortable bed, in a nice, dark room, at a good temperature and you're relaxing and your body is relaxing and resting, you are getting benefit and rest from that. Taking some of our ideas and putting together what is right for you personally may be very helpful. I think warm baths before bed—I do think tea is very helpful. The screens really will hurt you. I know for myself, if someone calls me or I have to look at my phone before bed, it does postpone when I could fall asleep. Anything that makes you have that adrenaline surge—it's really hard to fall asleep after that. Just do your best to lower all the stress levels as much as you can.

Chin: Yeah, I love those suggestions, Allison. Even the way you described lying in bed, resting, letting your body rest—it's very therapeutic to think of it that way, even if you're not sleeping at that moment. I think that's a nice way of framing it so that we don't get stressed, because certainly, I think it's understandable to feel stressed when we're not sleeping because we know we should be sleeping. That's a really, really good point. Now, Allison, I brought up melatonin as something someone might consider. Ultimately, I'm really just getting at the importance of establishing and maintaining a circadian rhythm, which is something you're interested in. Could you share with our listeners the importance of one’s circadian rhythm? What exactly is it, and how is it impacting our sleep?

Reiss: Well, you know, this is a relatively new area where we're recognizing how important it is. We all have what's called clock genes. We all live on the cycle of the 24-hour day, and our regular sleeping and waking. Most of us—our bodies and our brains—don't sleep during the day. We want to be out in the light, and we don’t want to stay awake at night. A lot of people don’t have a choice. If you do international travel, shift work, if you're in places with a lot of artificial lighting, you disturb these rhythms.These rhythms are really down to our cellular level. There's definitely a back and forth between sleep and neurodegeneration. We know that when we have nerves that are not working well in people who have cognitive problems, the circadian rhythm is disrupted, and there are sleep disorders. On the other hand, sleep disruption may hurt your brain by causing inflammation and interrupting that clearance of protein debris in the brain. It's a back-and-forth connection—good sleep helps your brain do better, and when your brain isn't doing as well as it should, it may cause you to disrupt your sleep. We want to keep–as much as possible–a good and regular sleep schedule and try to keep everything with the light and dark cycles. That gets hard sometimes, especially, you know, if there is very little light during the winter when it's a short day. A lot of studies show that if you get some good light exposure early in the day, it can help you sleep better at night and have better cognition. Unfortunately, nighttime light exposure, which has been found to be associated with more risk of Alzheimer's disease, is increasing because of all the light around us, like the light pollution that's everywhere. Blackout curtains, an eye mask—something to make sure that you really are sleeping in the dark. I think that's helpful. Sleep is so foundational for our health, but not everyone has that natural gift to sleep, and some people seem to just not need as much sleep as others. Do you think people can function on less than six hours of sleep, Nate? Are they still at risk for Alzheimer's if they're sleeping only a few hours a night?

Chin: Yeah, this is a great question. It's one I think many people wonder about. I do believe there are people out there that may do well with less sleep. Frankly, I envy them, but it's likely there's something about them genetically that allows them to sustain their ability to function well for a long period of time with little sleep. I think the reality is I'm not sure how many of them truly exist. We hear about a lot of them, but I'm not sure how many are in this group that truly are able to do it. So I think of them as the exception and not the rule, and not something that we should—certainly as we're in our adult life—think that we are now somehow one of them. If we haven't been one of them since we were young, it's likely we're not one of them now. Most of us can do okay, though, with less sleep for short periods of time, but there are studies showing the negative impact of sleep on our abilities. Even if we report feeling okay, when they do those thinking tests on us or they do something else, we do see that there are declines. I think this speaks to the tenacity of people, though. We get things done. We know how to do work. We know how to accomplish our goals. We say that we're feeling fine, even if we're not really at our optimal. Of course, I mentioned people who do shift work, or parents, or anyone who's really in this chronic state of sleep deprivation. People just live with it, which means they're tough, of course, but it's not optimal. I think whenever we have the opportunity to improve our health, we should try to take that. I think when it comes to "Am I someone who can thrive on four hours?"—maybe, maybe not. Maybe you should focus on "What can I do so that I can move from four hours to six hours and feel better?" I don't know if these unique individuals not needing sleep are at higher risk of Alzheimer's disease or future declines, but maybe you know, Allison—I'm just not aware of any of those studies.

Reiss: Well, it's just really not clear. Sometimes we just don't have the full answer, but there are some studies that really do show if you are middle-aged, like 50, 60, and you are sleeping less than six hours, and we compare those people with people who sleep seven hours or more, we see a 30 percent increased dementia risk in those people who are getting little sleep. That was a study called the Whitehall II study. There are a lot of studies like this. I have to say, I suspect that some of the people who say they're getting so little sleep, they're not really getting that little sleep. They're having micro naps or something is going on where they're sleeping. So we have to also understand that quantitating people's sleep over long periods, in reality, it's not so practical to really try to do that. We're probably not getting the best accuracy.

Chin: I appreciate that answer. Don't compare yourself to others. You don't really know what's going on in their situation. Just see how you're feeling. Allison, I'd like to end our conversation today with a difficult question that I get asked a lot from my female patients. Why are women more likely than men to develop insomnia, especially as they grow older?

Reiss: Again, we don't have all the answers, but we have some thoughts about some of the things that may be contributing. I think a lot of women will notice that menopause and perimenopause kind of bring on an onset of not sleeping as well as they used to. They'll recall fondly younger years where they slept better. Some of that is probably just your whole hormonal system being out of whack causes lots of disruption that affects sleep. Like the hot flashes, the night sweats—these really do increase that risk of insomnia. There's also more likelihood with some weight gain and sleep apnea and mood changes, depression and anxiety. We know that mood changes really do diminish your sleep quality. Women are also more affected by stress. You know, they're—they're not as able to kind of compensate a lot of times, and they're more likely to lose sleep over stress. They have a lot of pressures—societal, work, family pressures—that are going to affect the circadian rhythms and so many responsibilities that list in your head that never stop growing. They also are more likely than men to be in pain. Migraines certainly are, you know, very disruptive of sleep. Carpal tunnel, irritable bowel, rheumatoid arthritis, all different kinds of arthritis and fibromyalgia—it's very hard to sleep when you're in pain. I think there are just so many things that maybe have more effect on women than men. Whatever your gender, I think it is so helpful to sleep, to get outside and be in nature and not sit indoors all the time. I think these are some of the old-fashioned things, you know, that we were told by our moms and grandmothers, like go out and play or go out and be out in the sun and out in the world, get your vitamin D. I think that's also very important. You will sleep better if you tire yourself out by doing things. Being sedentary and sitting in a chair does not prime you to sleep well.

Chin: Allison, I love your answer, and it reinforces a key message that we need to talk openly about sleep issues. We need to address the factors that are within our control and then certainly talk to our healthcare providers about interventions or just ideas to improve our sleep. It's worth the effort to get better sleep for our bodies and our brains. So thank you for coming on Dementia Matters and talking about this very important topic with us.

Reiss: It was an incredible pleasure. It was such an honor to talk to you. Any way that we get information to the public and there's no cost or financial barrier—this is something that I think is a beautiful thing. Thank you so much, Nate.

Outro: Thank you for listening to Dementia Matters. Follow us on Apple Podcasts, Spotify, or wherever you listen or tell your smart speaker to play the Dementia Matters podcast. Please rate us on your favorite podcast app – it helps other people find our show and lets us know how we are doing. If you enjoy our show and want to support our work, consider making a gift to the Dementia Matters Fund through the UW Initiative To End Alzheimer’s. All donations go towards outreach and production. Donate at the link in the description. Dementia Matters is brought to you by the Wisconsin Alzheimer's Disease Research Center at the University of Wisconsin–Madison. It receives funding from private, university, state and national sources, including a grant from the National Institutes on Aging for Alzheimer's Disease Research Centers. This episode of Dementia Matters was produced by Amy Lambright Murphy and Caoilfhinn Rauwerdink and edited by Eli Gadbury. Our musical jingle is "Cases to Rest" by Blue Dot Sessions. To learn more about the Wisconsin Alzheimer's Disease Research Center, check out our website at adrc.wisc.edu, and follow us on Facebook and Twitter. If you have any questions or comments, email us at dementiamatters@medicine.wisc.edu. Thanks for listening.