"Guest. This Week is Dr Matthew Walker Who who earned his neuroscience degrees over in the UK and then became a professor of psychiatry at Harvard Medical School and is right now a professor esser of neuroscience and psychology at the University of California in Berkeley He wrote a bestselling book called. Why we sleep and we're doing a two part episode this week in the first part were talking about All the things all the unfortunate things that can happen to you when you don't get enough sleep up to your heart to your brain to other parts of your body were talking about the Link between sleep and mental health. What kind of impact? Meditation can have on asleep and the stigma in our society around sleep and then we so we did have an hour together on that several months ago actually we. I recorded that first hour our and then we took a couple of months break and I started to wear a sleep tracking ring and so we go back to Matthew for another chunk of this interview where we talk about my data and many other questions. That are fascinating so here we go with part one of the interview with Matthew Walker on sleep pleasure to meet you. I kind of feel like I know you after having listened to somebody podcast will likewise to you. I have to say so. Our relationship goes by my gears at this stage to see old friends and and you have had As I was saying to you earlier you really had an impact of the way I think about sleep so I'm excited to pass that along to our listeners and viewers so let me just ask some biographical stuff. How did you get interested in sleep in the first place I don't think anyone you know when the five or six years old and you go around the classroom you say. What would you like to be when you grow up? No one shoots. The differences have lived to be asleep research. Yeah and I think we're all accidental sleet researches and I was the same so back join late. Phd Work I was looking at brainwave patterns in people with dementia early early stages and I was trying to differentially diagnose what form of dementia that they had was it sort of vascular dementia or Alzheimer's Disease and was failing thing miserably and he used to go home at the weekends with the stack of journals. And I put them in my doctor's residence Igloo of information around me and when we can I was reading that some of the centers that certain types of dementia would eat away at in the brain was sleep generating centers and then for other types of dementia the left those centers untouched. So I thought well I'm measuring the brainwave pattern of my patients at the wrong time. which is when they're awake should be measuring it? When they're asleep sleep started doing that? Great Results and at that point I thought maybe the sleep disruption is not just a symptom of the dementia. I wonder if it's actually a causal causal trigger and that's when I just fell headlong into this field of sleep research and at that time no one could answer the question. Why do we sleep? This is twenty years ago. The crass answer was that we sleep to cure sleepiness which is the factors equivalent of saying to cure hunger. It tells you nothing about the biological benefits of nutrition. We really do nothing about why we why we sleep. Twenty years ago we just had very little understanding other than that. It was deathly if you removed it and they did these cities Um some studies that probably will never be replicated again for ethical reasons in rats. Let's and they decided to deprive the rats completely off sleep. I'm what they found. Is that those. Rats would die as quickly from sleep deprivation as they would from food deprivation within ten eleven days and so we own the on the cusp of realizing how fundamentally necessary sleep was i. Then I thought well if nobody knows it right now I'll just come along and for two years out. Go to America and I went to Boston. I thought I'll crack that question with total naievety not Hubris. I'm not realizing that. Some of the most brilliant minds it failed to crack the question and as I said that was twenty years ago and I think hard license little about who asks them they will meet her out their lessons. Difficulty all the same And I've been schooled over the years. So what do we know about why we sleep. Well it's fascinating over the past twenty years. We've fat explosion of knowledge. In fact we've had to upend that question rather than saying. Why do we sleep? We've now had to ask Is there anything that sleep doesn't serve in terms of a benefit for either the brain the body and the answer seems to be no. There is no single tissue within the body nor process of the mind but isn't wonderfully enhance when we get sleep demonstrably strictly imposed when we don't get enough so walk me through the reasons why we should be attending so carefully to our sleep. If we don't get enough sleep what happens so let me start in the body and we'll just go through may be the major physiological systems. So firstly I'm reproductive-health health what we know is that men who sleeping just four to five hours a night. We'll have a level of testosterone. which is that of someone? Ten years their senior so a lack of sleep will age by decade in terms of that aspect of wellness realty. We see Quin pumps and female reproductive health caused by lack of sleep. I'm stepping away from the reproductive system. We also know that. A lack of sleep dramatic impact on your cardiovascular system there's a great example From perhaps the largest sleeps that he ever done. It affects one point. Six billion people it is undertaken across about sixty different countries twice a year. And it's called daylight savings time now in the spring when we lose one hour of sleep we see a subsequent subsequent twenty four percent increase in heart attacks the following day which stuns me In the autumn in the full when we gain an hour of sleep we see a twenty one percent reduction in heart attacks. That's how fragile and vulnerable cardio-vascular systems out by the way you see exactly the same profile for road traffic accidents on Australia. Even suicide rates following daylight savings time. I'll speak about the immune system though because that's something else. That's fundamentally regulated by lack of sleep. It doesn't require whole night of sleep deprivation I can take an individual and we can deprive you you. Let's say a four hours of sleep so you get four hours that one night and then the next day. We measure some critical anti-cancer fighting immune cells called natural killer cells. And they're almost like the secret service agents of your immune system. They're very good at identifying malignant humans and destroying them after one night eight of four hours of sleep we see seventy percent drop in these natural killer cells these critical anti-kaunda fighting cells and we could just sort of keep stepping through The body but let me just take a moment to go upstairs in the brain because sleep is not just feel body. It's in fact by the brain of the brain. And perhaps most importantly for the brain one of the most favoured diseases in developed nations is outside this disease and what we've discovered over the past five years now is that there's a remarkable sewage system in your brain that kicks into high gear at night light while we sleep and that sewage system is called the glymph attic system. Now you have a similar system in your body that everyone knows. It's called the lymphatic system. But we didn't realize the brain also has a cleansing system gleam fat exist and one of the sort of toxic metabolic byproducts products. That sleep using the system will wash away at night is a sticky toxic protein. Cool beat amyloid. Beta amyloid is one of the protein protein culprits underlying Alzheimer's disease. And so what we see is that even after one night you can bring perfectly healthy people into the laboratory. You can actually remove the sleep or even just selectively remove the deep sleep which is when that sort of system. That's a good night's sleep. Clean kind of power. Cleanse is actually happens you can selectively. Remove that type of sleep and the next day you do. What's called spinal cord puncture and you siphon off some of the fluid who volunteers for this kind of study you have to pay them rather a lot of money and be very nice to them and they never do this study the again? Probably so what we find that measure of cerebrospinal fluid that we take from the spinal cord tells us what's going on in the brain and you see an immediate next next day rise in the amount of this beater amyloid toxic protein circulating in the system and this is in healthy people have to just one night so who now you can imagine what happens if you scale that across weeks years. It's like compounding interest on alone every night that you'll show changing your brain of sleep. You're not cleansing. The brain of that be to amyloid toxic Alzheimer's protein and so it starts to scale and it doesn't scale in a linear fashion. Because it's an an exponential and that's exactly what we see with Alzheimer's disease as a patent of pathology and as a of cognitive decline and just last year we published. There's evidence that those two things that as you get older your sleep gets worse and as you get older your memory gets worse those two things on simply coincidental they're actually closely closely interrelated then so really understanding so much more now about The fundamental role that sleep placing every one of these physiological systems systems in the body and operations of the mind we can also speak about sleep and mental health. Hopefully at some point that link is incredibly"