Why We Need Sleep – Dr. Matthew Walker on Revolution Health Radio, Hosted by Chris Kresser

Check out the Revolution Health Radio Episode Page & Show Notes

Key Takeaways

  • “Most tissue and physiological systems in the body, as well as most operations of the mind, are powerfully enhanced with sleep, and quite demonstrably impaired when we don’t get enough”Dr. Matthew Walker
  • “The number of people who can survive on 7 hours of sleep or less without showing any biological or cognitive impairment rounded to a whole number and expressed as a percent of the population is 0”Dr. Matthew Walker
  • You don’t know you’re sleep deprived when you’re sleep-deprived
  • If you didn’t set an alarm, would you sleep past the time you usually set it for?
    • If the answer is “yes,” then you’re body/brain isn’t done sleeping and you clearly need more
  • 5 tips to improve your sleep:
    • Go to bed and wake up at the same time EVERY day – regularity is KEY
    • Sleep in a cooler environment – your body needs to drop its core temperature by 2-3 °F to fall asleep and stay asleep
    • 1-2 hours before bed, do your best to 1) avoid screens and 2) dim/turn off the lights in your house
    • If you go to lay down and haven’t fallen asleep within 20-25 minutes, get out of bed and go read in dim light
    • Stay away from alcohol and caffeine

Products Mentioned

  • Chris uses the OOLER Sleep System, a mattress topper that circulates temperature-controlled water (varying between 55-110 °F), allowing you to optimize your sleep environment (with the OOLER, you can schedule temperature changes throughout the night)
    • For 15% off the OOLER, use the code “Podcastnotes15” at checkout
  • If you absolutely have to use your laptop or phone at night, wear blue light blocking glasses

Intro

On Academic Life

  • “What I love about science is that it’s incredibly intellectually fulfilling, but an academic life is very much devoid of emotional fulfillment. It’s almost egotistical – What grants are you getting? What podcasts are you on? Where are you publishing? What awards have you won?” – Dr. Matthew Walker
    • “Where I get my emotional nourishment from is teaching; I adore teaching… You can’t have an ego in that regard, not if you’re going to be a good teacher.”

Why do we sleep?

  • Many years ago, we simply thought “we slept to cure sleepiness”
  • But now, we’re facing different (more significant) questions: “Is there anything that sleep does not provide in terms of a functional benefit to the brain and body?”
    • (It doesn’t look like it)
      • “Most tissue and physiological systems in the body, and most operations of the mind, are powerfully enhanced with sleep, and quite demonstrably impaired when we don’t get enough”Dr. Matthew Walker

Why did we evolve to sleep?

  • Sleep must be important because:
    • It leaves you vulnerable to predation
    • It takes away from time you could be spending searching for food or a mate
  • “If sleep doesn’t support an absolutely vital set of functions, it’s going to be the biggest mistake the evolutionary process ever made” Dr. Matthew Walker
    • “Sleep has fought its way, heroically, every step of the evolutionary path. If it’s that well-preserved, how could it not be essential?”
  • Matt has an interesting theory:
    • Perhaps we didn’t evolve to sleep, but in fact, we started from sleep and from that wakefulness emerged

How has sleep evolved over time?

  • Hunter-gather tribes didn’t quite sleep the way we do in terms of timing; Matt explains:
    • For them, midnight literally means “middle of the night” – they went to bed shortly after sundown and woke up around dawn
    • For us, midnight is the last time we open Instagram or check our email
  • Secondly, hunter-gatherers tended to sleep biphasically: 6.5-7 hours at once with an additional ~1-hour nap in the early afternoon
    • In first-world nations, we sleep monophasically (in one bout)

Does everybody need 8 hours of sleep?

  • “The number of people who can survive on 7 hours of sleep or less without showing any biological or cognitive impairment rounded to a whole number and expressed as a percent of the population is 0” Dr. Matthew Walker
  • That said, a tiny percentage of people have the DEC2 gene, a genetic mutation that produces a short sleeping phenotype
    • In other terms, these people have a lower need for sleep
    • BUT: You’re far more likely to be struck by lightning than have this gene
    • To add: If people with this gene are taken into a sleep lab without their phones, and allowed to sleep as much as they want/can, they tend to sleep 6.25 hours/night
      • These are genetic mutants, and they’re getting slightly less sleep than the average American adult (6 hours and 31 minutes)!!
    • We’ve only just discovered this genetic mutation, and it’s yet to be determined if these people have a shorter lifespan 

You ARE Affected by a Lack of Sleep

  • “You don’t know you’re sleep-deprived when you’re sleep-deprived. Your subjective sense of how well you’re doing is a miserable predictor of objectively how well you’re doing.” – Dr. Matthew Walker
    • A good analogy: Someone who’s drunk thinking they’re okay to drive
  • “A lot of people are carrying a chronic sleep debt, and they truly don’t know how good a version of themselves, mentally and physically, they could be if only they slept enough.”Dr. Matthew Walker

How do you know how much sleep you need?

  • If you didn’t set an alarm, would you sleep past the time you usually set it for?
    • If the answer is “yes,” then you’re body/brain isn’t done sleeping and you clearly need more
  • In general, you need 7-9 hours of ACTUAL sleep (not time in bed)
    • So, to make this feasible, give yourself 8.5-9.5 hours in bed
  • Of the total amount of time you’re in bed, the higher your sleep efficiency, the more of that time you’ll actually spend sleeping
    • Healthy people tend to have a sleep efficiency score of >85%

Sleep Tracking

  • “Most of the devices out there right now, the wristwatches or ring, do a pretty good job of differentiating basic total sleep time. The problem is, they’re not very good at separating out the basic sleep stages.” – Dr. Matthew Walker
  • Another problem with sleep trackers: 
    • When we go to sleep, we’re accustomed to taking things off, not putting things on (like wristbands or headbands)
  • Matt is personally excited about mattress-based sleep trackers (like that from Eight Sleep)
    • Comparing a car today to one from the 1950s, it’s packed full of sensors that continuously monitor the health of the vehicle
    • But, comparing a 1950s mattress to one today, they’re pretty similar (even though we spend 30%+ of our lives in bed)

Chronotypes | Does it matter when you sleep?

  • Some people are night owls, some are morning larks, and others are in between
    • ~1/3 people fill each bucket
  • Your chronotype is genetically defined
    • That said, it can change over time, particularly through adolescence (to a later time-frame) and in later life (to an earlier time-frame)
  • Many people don’t actually have insomnia, they instead have a mismatch between their enforced sleep window and their biological chronotype (AKA they’re getting into bed when their biology and physiology isn’t ready to sleep)

Effects of Later School Start Times

  • (As teens tend to have later chronotypes, there’s a movement to push back school start times)
  • Academic grades increase
  • Truancy rates decrease
  • Behavioral problems decrease
  • Psychological and psychiatric referrals decrease
  • Life expectancy increases (due to a decrease in car accidents)
    • Matt recalls some data: One school in Wyoming shifted their start time from 7:35 AM to 8:55 AM and saw a 70% drop in car crashes 
      • “To put that in context, the advent of ABS technology in cars, anti-lock brake systems, dropped accident rates by 20-25% and it was deemed a revolution” – Dr. Matthew Walker
    • Matt adds: “If our goal as educators truly is to educate and not risk lives in the process, then we are failing our children in the most spectacular manner with this incessant model of early school start times” Dr. Matthew Walker
      • “When sleep is abundant, minds flourish, and when it’s not, they don’t”

You Can’t “Catch Up on Sleep”

  • “Sleep is not like the bank; you can’t accumulate a debt and hope to pay it off at a later point in time” – Dr. Matthew Walker
  • Many people are sleep-deprived during the week, and then try to catch up during the weekend 
    • “This isn’t good. It creates what we call ‘social jetlag'” – Dr. Matthew Walker
    • Matt explains: If you’re going to bed ~midnight on Friday/Saturday (and waking up around 10-11 AM), and come Sunday night you try to drag your biological clock back to going to bed at 10 PM, it’s essentially like flying back and forth from NY to SF every weekend

What about naps?

  • During the day, we build up a chemical that causes us to feel sleepy (adenosine). Because of this, the longer you’re awake, the more tired you’ll feel. 
    • During sleep, the brain clears away adenosine (so napping in the late afternoon may cause you to have trouble falling asleep come nighttime)

The Best Sleep Tip

  • “The first piece of advice I can give you for better sleep is regularity: go to bed at the same time and wake up at the same time, no matter if it’s a weekday or the weekend” Dr. Matthew Walker

Meditation Can Help You Sleep

  • “For people who are struggling with sleep at night, meditation has been proven to be very advantageous” – Dr. Matthew Walker

Insomnia (Beware of Sleeping Pills)

  • There are two types:
    • Sleep onset (having trouble falling asleep)
    • Sleep maintenance (having trouble staying asleep)
  • Are there any recommend cures?
    • DON’T taking sleeping pills (like Ambien); they increase the risk of overall mortality and cancer
      • To add, these drugs don’t actually stimulate real “sleep” – it’s more of a “sedation”
      • “Sleep, if you understand the biology, is an incredibly complex physiological ballet of different things. To think we could orchestrate that ballet with a simple basic drug is unlikely.” – Dr. Matthew Walker
    • Cognitive behavioral therapy for insomnia (CBTI) has proven to be a remarkably advantageous treatment

How to Improve Your Sleep (Part I)

  • Go to bed and wake up at the same time EVERY day
    • “If you only remember one thing from this podcast, it should be this” – Dr. Mathew Walker
  • Regulate temperature
    • “Your body needs to drop its core temperature by 2-3 °F to fall asleep and stay asleep. This is the reason you’ll always find it easier to fall asleep in a room that’s too cold, as opposed to one that’s too hot”Dr. Mathew Walker
      • A few ways to facilitate this temperature drop: 
        • Wear socks and gloves to bed (this causes blood to be drawn away from your core, thus cooling you down)
        • Take a hot bath or shower before bed – when you get out, you experience a substantial thermal dissipation of heat which drops your core body temperature
    • A bedroom temperature of 67 °F is optimal for most people
    • Chris uses the OOLER Sleep System, a mattress topper that circulates temperature-controlled water (varying between 55-110 °F), allowing you to optimize your sleep environment (with the OOLER, you can schedule temperature changes throughout the night)
      • For 15% off the OOLER, use the code “Podcastnotes15” at checkout
  • Pay attention to darkness
    • Avoid screen use ~1 hour before bed
      • 1 hour of iPad reading before bed has been shown to reduce melatonin production by 50%, delay the peak of that melatonin release by 3 hours, and reduce REM sleep
      • If you absolutely have to use your laptop or phone, wear blue light blocking glasses
    • Also, try to dim the lights in your house (or turn them off) 1-2 hours before bed

How to Improve Your Sleep (Part II)

  • Walk it out – don’t remain in bed awake too long (~20-20 minutes)
    • If you lay down and haven’t fallen asleep within 20-25 minutes, get out of bed and go read in dim light
      • Then, only return to bed when you’re sleepy
    • Why?
      • “Your brain is an incredible associative device, and very quickly it learns that your bed is a place of being awake, not asleep” – Dr. Matthew Walker
      • Also: “You’d never sit at the dinner table waiting to get hungry, so why would you lie in bed waiting to get sleepy?” – Dr. Matthew Walker
  • Stay away from alcohol and caffeine
    • Caffeine has a half-life of 6 hours and a quarter-life of 12 hours
      • Thus, 6 hours after consuming a cup of coffee, half of the caffeine is still swirling around in your brain
      • Or, similarly, 12 hours after drinking a cup of coffee, a quarter of its caffeine is still affecting you
        • “Having a coffee at noon is the equivalent of tucking yourself into bed at midnight, and before you turn the light off, swigging a quarter of a cup of Starbucks and hoping for a good night of sleep”Dr. Matthew Walker
      • Even if you have no trouble falling asleep a few hours after a shot of espresso, the depth of your deep sleep ~20% impaired
    • Alcohol may help you fall asleep faster, but it’s not actual sleep – it’s more sedation (like sleeping pills)
      • Secondly, alcohol fragments your sleep
      • Thirdly, alcohol also blocks REM sleep

Sleep is the Archimedes Lever

  • Good sleep improves every aspect of your life – cardiovascular health, mental health, glucose regulation, etc.
    • “If you focus on sleep, you’ll be doing a remarkable service to your healthspan and lifespan” Dr. Matthew Walker
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