Matthew Walker, Ph.D., on Sleep – Part I of III: Dangers of Poor Sleep, Alzheimer’s Risk, Mental Health, Memory Consolidation, and More – The Peter Attia Drive

Check out The Peter Attia Drive Episode Page & Show Notes

Key Takeaways

  • A lack of sleep is one of the most significant lifestyle factors that determines your risk for Alzheimer’s Disease
    • During the deep stages of sleep, the brain’s glymphatic system kicks into high gear and clears away metabolic waste that accumulates while we’re awake
      • One of the substances that the glymphatic system washes away is called beta-amyloid (one of the two core proteins whose build up is thought to contribute to Alzheimer’s Disease)
  • The stages of sleep:
    • Non-REM (N-REM)
      • Stage 1, 2, 3, and 4
        • Stages 1 and 2 are lighter
        • Stages 3 and 4 are the deepest/most restorative
    • REM (rapid eye movement)
  • Here’s what a typical 90-minute sleep cycle looks like:
    • When you’re lying in bed with your eyes closed, the back of the brain goes into an “alpha rhythm” and starts to settle down
      • The back part of the brain stops processing the outside world and slows the frequency of its brain waves (from 50 cycles/second to 10 cycles/second)
    • As you begin to fall asleep, your eyeballs start to roll in your sockets (called “slow rolling eye movements”)
    • Then you enter Stage 1 and 2 N-REM sleep
      • In Stage 1, alpha brain waves are diminished, and theta brain waves start to appear
      • In Stage 2, the frequency of brain waves (now all theta) is ~6-7 cycles/second
        • The amplitude of the waves also increases
        • During this stage, sleep spindles occur
    • After 20 minutes, you enter into Stage 3 and 4 N-REM sleep (deep sleep)
      • At this point, the brain’s waves (now delta waves) are more slow/chant-like (1-2 cycles/second) – the amplitude of these waves are very large
    • After about 70 minutes, you fall back into Stage 2, and then transfer into REM sleep
    • Then you fall back into Stage 1, completing the 90-minute cycle
  • As the night goes on…
    • In the first half – the majority of your 90-minute sleep cycles are comprised of deep N-REM sleep, and little REM sleep
    • In the second half – the majority of your sleep cycles are comprised more of REM sleep, and almost no deep sleep
      • THIS IS WHY YOU CAN’T JUST SLEEP 5-6 HOURS/NIGHT – YOU MISS OUT ON A TON (ALMOST ALL) OF YOUR REM SLEEP
  • With a lack of REM sleep, you’re more prone to mental health issues (like depression, anxiety, and suicidality)
  • Adults around the world are now sleeping less than ever before

Intro

  • Dr. Matthew Walker (@sleepdiplomat) is the author of Why We Sleep and professor of neuroscience and psychology at the University of California, Berkeley
  • Matthew has been making the podcast rounds, check out:
    • The Podcast Notes from his appearance on the Found My Fitness podcast
    • The Podcast Notes from his appearance on The Joe Rogan Experience
    • The Podcast Notes from his appearance on The Jordan Harbinger Show
  • “Doctors are interested in answers, scientists are answered in questions” – Matt

The Relationship Between a Lack of Sleep and Alzheimer’s Disease

  • “Sleep, at this stage, may be one of the most significant lifestyle factors that determines your risk for Alzheimer’s Disease”
    • “I don’t make this statement lightly”
    • Why is this the case?
      • Wakefulness is essentially low-level brain damage – we need sleep to repair it
        • “Sleep is the price that we pay for wakefulness”
        • Insufficient sleep results in an increase of oxidative stress in the brain which leads to a whole cascade of negative effects, eventually causing neuronal death
          • The hippocampus, a critical memory center of the brain, is most sensitive to this neuronal death
          • The hippocampus is one of the first areas of the brain to undergo damage in the Alzheimer’s Disease process
      • It’s been discovered that the brain has its own sewage system (just like the body’s lymphatic system) – the glymphatic system (named after the glial cells of the brain which surround our neurons)
        • During the deep stages of sleep, this sewage system kicks into high gear
          • The glial cells shrink in size by up to 200%, leaving a ton of room for cerebral spinal fluid to perfuse and wash away the brain’s metabolic waste that accumulates while we’re awake
        • What does this have to do with Alzheimer’s Disease?
          • One of the substances the glymphatic system washes away is called beta-amyloid (one of the two core proteins whose build up is thought to contribute to Alzheimer’s Disease)
            • So each night, if you’re not getting enough deep sleep, you’re accumulating more and more beta-amyloid plaques in the brain, escalating your risk for Alzheimer’s Disease
          • Data:
            • Adults who get 7 hours of sleep or less have significantly more amyloid build up than those getting 7+ hours
            • Depriving animals (rats) of deep sleep, or even just fragmenting their sleep, immediately results in a build up of amyloid plaque
            • By depriving a human of the deep stages of sleep (by playing certain auditory tones during their sleep), and still having them get a full 8 hours of sleep – there is a significant increase in circulating levels of amyloid protein (and tau – another protein related to Alzheimer’s Disease) (measured via a spinal tap)
  • Perhaps in the future, we’ll start categorizing Alzheimer’s Disease
    • For example – sleep fragmentation will lead to one type of Alzheimer’s Disease and a lack of deep sleep will lead to another type of Alzheimer’s Disease
  • Matt and his team are currently trying to figure out if there are certain decades (or ages) during an adult’s life where sleep is even more important in terms of amyloid/tau build up
    • They just submitted a paper related to this and are waiting for approval
    • Matt says that depending on which decade of life you’re in (or how old you are) more of either tau or amyloid protein will build up from a lack of sleep
      • Amyloid tends to build up more in your 30s-40s and 60s-70s
      • Tau protein tends to build up more in your 50s-80s

The Four Pillars of Sleep

  • Regularity
    • How consistent is your sleep schedule
  • Continuity
    • Is your sleep fragmented?
  • Quantity
    • How much total sleep you’re getting (and how much of each sleep stage)
  • Quality
    • The electrical signature of your sleep
    • Just because you’re getting 8 hours of sleep doesn’t mean you’re getting quality sleep
      • For example – circulating caffeine can reduce sleep quality

A Brilliant Point

  • Perhaps we didn’t evolve to sleep and it’s the other way around
    • Maybe the default state of life was once a state of sleep and it was from sleep that a state of wakefulness emerged
    • (This is just a hypothesis)

The Stages of Sleep

  • Non-REM (N-REM)
    • Stage 1, 2, 3, and 4
      • Stages 1 and 2 are lighter
      • Stages 3 and 4 are the deepest/most restorative
  • REM (rapid eye movement)

What does a typical sleep cycle look like?

  • When you’re lying in bed with your eyes closed, the back of the brain goes into an “alpha rhythm” and starts to settle down
    • Compare this to when you’re awake during the day – your brain shows frenetic high-frequency electrical activity with small amplitude brain waves
      • Why small amplitude? – Different parts of your brain are doing different things at different times, and the brain waves essentially cancel each other out
        • It’s similar to dangling a microphone above a sport’s stadium – you pick up the signal from 100,000 individual neurons that sit underneath it
    • The back part of the brain stops processing the outside world and slows the frequency of its brain waves (from 50 cycles/second to 10 cycles/second)
  • As you begin to fall asleep, your eyeballs start to roll in your sockets (called “slow rolling eye movements”)
    • We don’t know why this happens, but it’s the first sign you’re making the transition from the world of wakefulness to sleep (you can actually see this happen if you have a bed partner)
  • Then you enter Stage 1 and 2 N-REM sleep
    • In Stage 1, alpha brain waves are diminished, and theta brain waves start to appear
    • In Stage 2, the frequency of the brain’s waves (now all theta) is ~6-7 cycles/second
      • The amplitude of the waves also increases
      • During this stage, sleep spindles start to appear – synchronous bursts of electrical activity (aka k-complexes)
  • After 20 minutes, you enter into Stage 3 and 4 N-REM sleep (deep sleep)
    • At this point, the brain’s waves (now delta waves) are more slow/chant-like (1-2 cycles/second) – the amplitude of these waves are very large
      • Use the stadium analogy again – it’s like everyone in the crowd is now chanting the same thing, just very slowly
    • During these stages, lots of information transfer is taking place in the brain
      • “Deep sleep is a state of long-distance information transfer”
    • The waves are typically larger in amplitude and slower in frequency in Stage 4 compared to Stage 3
  • After about 70 minutes, you fall back into Stage 2, and then transfer into REM sleep
  • Then you fall back into Stage 1, completing the 90-minute cycle
  • Important notes
    • People always follow this chronological order, with the following exceptions:
      • With narcolepsy, you go straight from being awake into REM sleep
      • If you’re chronically REM sleep deprived, occasionally you can make the transition straight into REM sleep from being awake
        • This happens often for alcoholics, as alcohol inhibits REM sleep
    • As the night goes on…
      • In the first half – the majority of your 90-minute sleep cycles are comprised of deep N-REM sleep, and little REM
      • In the second half – the majority of your sleep cycles are comprised more of REM sleep, and almost no deep sleep
        • THIS IS WHY YOU CAN’T JUST SLEEP 5-6 HOURS/NIGHT – YOU MISS OUT ON A TON (ALMOST ALL) OF YOUR REM SLEEP
        • The deep sleep that you do get in the second half seems to be comprised mostly of Stage 2
    • The timing of your 8 hour sleep window determines which type of sleep you’re likely to get more of (deep vs. REM)
      • People with earlier sleep windows (9 PM – 5 AM) tend to experience more deep sleep and less REM
      • As the sleep window gets later (say it slides to 2 AM – 10 AM) – these people tend to get more REM sleep and less deep sleep

Sleep and Learning

  • You need sleep after learning to essentially hit the “save button” on your memories (to consolidate memories)
    • This is what deep sleep does
  • You need sleep before learning to prep the brain for receiving new memories
    • Stage 2 N-REM sleep does this (the sleep spindle stage)

The Importance of REM Sleep

  • With a lack of REM sleep, you’re more prone to mental health issues (like depression, anxiety, and suicidality)
    • “REM sleep is emotional first aid”
    • In young teens specifically, one of the strongest predictors of suicidal ideation (thoughts), suicide attempts, and suicide completion is insufficient sleep and sleep fragmentation
    • REM sleep seems to resets/recalibrate the emotional networks in the brain:
      • The middle part of the prefrontal cortex which acts as a top-down regulator of your emotions
      • The amygdala which is a centerpiece region for the generation of strong/impulsive negative reactions
    • (This is why it’s so important to let your child nap)

Sleep and Evolution

  • It’s taken mother nature 3.6 million years to put the 8 hour sleep window in place, and in the span of 70 years we’ve lopped off almost 20-25% of that
  • Think about sleep evolutionarily – it HAS to be important
    • If we weren’t sleeping, we could be hunting for food or finding a mate, and during sleep, we’re so vulnerable to attack
    • “If sleep doesn’t serve an absolutely vital set of functions, it’s the biggest mistake the evolutionary process has ever made”
    • “Sleep is the greatest life support system you could ever wish for. It’s a remarkable health insurance policy – it’s largely democratic, it’s mostly free, and in terms of a prescription from a doctor, it’s largely painless.”

Sleep, Diet, and Exercise

  • Sleep is the foundation on which diet and exercise sit
    • Think – If you deprive yourself of food, based on your body fat percentage you can survive 30-~350 days
    • Derivation of sleep results in the quickest reduction in health

Jet Lag Protocol

  • When Matthew travels from California to London, during the week before his flight he’ll try to wake up about 10 minutes earlier each day (London is 8 hours ahead of California)
    • The morning of his flight, he’ll wake up especially early
    • On his flight, he’ll sleep during the first half (when most people in London are asleep) and wake up at the start of the second half (when people in London are starting to wake up)
  • When Peter travels between NY and California, he generally tries to just stay on California time while he’s in NY

Which stage of sleep is most important?

  • One study on rats found the following, they were:
    • Dead within 9-10 days from total sleep deprivation
    • Dead within 9-10 days from REM sleep deprivation (total sleep duration was slightly reduced)
    • Dead within 20 days from N-REM (deep) sleep deprivation (total sleep duration was slightly reduced)
  • Deep and REM sleep didn’t appear at the same time evolutionarily
    • REM sleep only exists in birds and mammals, not in reptiles, fish, or insects
      • “REM sleep is the new kid on the block in the time course of evolution”
    • Deep N-REM sleep exists in every species 

The Dangers of Drowsy Driving

  • If you fall asleep at the wheel while driving 60 MPH, at a moderate drift angle you’re essentially in the next lane in less than a second and the ditch after another second
  • Microsleeps:
    • These are small lapses in consciousness where the eyelids partially close 
    • The more sleep deprived you are on the road, the more likely these are to occur
  • “Drowsy driving accounts for more accidents on our roads than either drugs or alcohol combined”
    • When you’re drunk you can still react (albeit slowly)
      • But when you have a microsleep at the wheel….nothing
        • “It’s like you’re driving a 2 ton missile on the freeway with no control”

Matt’s Book – Why We Sleep

  • Peter calls the book exceptional
  • “We will look back at the way we think about night-time electronics and sleep deprivation in 20 years, hopefully sooner, the way you and I look back at a smoking pregnant woman” – Peter
  • “The erosion of sleep has hit an all-time high. We are now sleeping less than we have ever done in what seems to be the history of our species”
    • In 1942, the average American adult was sleeping 7.5 hours/night
      • Now this number is down to 6 hours and 31 minutes (it’s been a nonlinear decline)
      • In Japan, this number is down to 6 hours and 21 minutes
      • In the U.K. – 6 hours and 49 minutes
  • “There is no physiological system in the body and no operation of the brain that isn’t wonderfully enhanced by sleep when you get it or demonstrably impaired when you don’t get enough”

Random

  • Every night, Matthew gives himself a non-negotiable 8 hour sleep opportunity
    • “That’s not because I’m trying to practice what I preach…If you understood what I know about sleep and all-cause mortality as well as most disease processes, you would realize I’m being nothing short of utterly selfish in my preservation of an 8 hour sleep opportunity. I don’t want to die young and I don’t want sickness and disease in my life.”
  • “Deep sleep is probably the best form of blood pressure medication you could ask for”
  • Peter estimates that during his medical school residency he was only getting about 28 hours of sleep per week (around 4 hours per night, on average)
  • The Guinness Book of World Records has refused to acknowledge attempts at breaking the world record for the longest period without sleep (which is currently about 24 days)
  • Fatal familial insomnia is a rare disease in which people are unable to sleep at all
    • It takes about 18-24 months until the individual dies
      • But the disease is gradual – it starts as general insomnia, then you’re only able to sleep 2-4 hours by month 12 etc.
    • The disease is strongly heredity (it’s a prion protein gene abnormality)
      • Mad cow disease is another prion protein disorder
  • “The shorter your sleep, the shorter your life”

These notes were edited by RoRoPa Editing Services

Bookmark
Facebooktwitterredditmail

Add a Comment

Your email address will not be published. Required fields are marked *

This site uses Akismet to reduce spam. Learn how your comment data is processed.

Don't Miss Out!

The top Takeaways, Lessons, Learnings and Quotes from the BEST podcasts each week in your inbox every Monday

Before You Go, Don't Miss Out!

The top Takeaways, Lessons, Learnings and Quotes from the BEST podcasts each week in your inbox every Monday