Dr. Matthew Walker on Sleep: Heart Disease, Cancer, Sexual Function, and the Causes of Sleep Disruption – The Peter Attia Drive (Part II)

Check out The Peter Attia Drive Episode Page & Show Notes

Check out the Podcast Notes for Part I

Key Takeaways

  • Some of the consequences from a lack of sleep:
    • Cardiovascular disease is accelerated
    • The reproductive hormones get out of whack:
      • Men who are sleeping 5-6 hours/night will have a level of testosterone that of 10 years their senior
      • Women sleeping 5-6 hours/night show a 20% reduction in follicle stimulating hormone (FSH) – a critical hormone for getting pregnant
    • Our immune system’s function is severely inhibited
  • “Human beings are the only species that deliberately deprive themselves of sleep for no apparent reason”
  • Sleep isn’t like the bank – you can’t accumulate sleep debt during the week and sleep it off on the weekends
  • Only 11% of 18-year-olds are getting sufficient sleep (most only get ~6-7 hours when they need 9-10)
  • Using an iPad (or a phone) for an hour before bed causes a 50% drop in the melatonin that’s released AND that melatonin peak will be delayed by 3 hours
    • An hour of iPad use before bed also reduces the amount of REM sleep you’ll get
  • Sleep is basically about balancing the following hormones: adenosine, cortisol, and melatonin
    • Adenosine accumulates throughout the day and makes you sleepy
      • (Caffeine acts to blunt adenosine build up)
      • When we sleep, adenosine is cleared away
    • Melatonin is the hormone that rises when it gets dark to signal to our body it’s time for bed
    • Cortisol levels typically rise when you wake up – this allows you to be awake/alert throughout the day
      • As night comes on, cortisol needs to drop in order for you to initiate sleep

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

Cardiovascular Disease is Accelerated by Sleep Deprivation

  • Let’s look at daylight savings time:
    • In the spring (when we lose an hour of sleep) – there’s a 24% rise in heart attacks the following day
    • In the fall (when we gain an hour of sleep) – there’s a 21% reduction in heart attacks the following day
    • Related:
      • The same profile happens for car accidents and suicide attempts/completions
      • Federal judges actually hand out harsher sentences during daylight savings time in the spring when we lose an hour of sleep (they’re moodier and less empathetic)
        • In the fall – more lenient sentences
  • One study found that getting an average of 5 hours of sleep or less over a 5 year period leads to a 200-300% increased risk for calcification of the coronary artery
    • Why?
      • People who are underslept have overactive sympathetic nervous systems (the flight or fight nervous system)
        • This results in more circulating adrenaline, higher spikes of cortisol, and blunted levels of growth hormone (all of which are tied to cardiovascular disease)
  • A loss of only 3 hours of sleep will result in:
    • An increase in blood pressure
    • An increase in heart rate

Sleep and Diet

  • Building off the increased risk for cardiovascular disease from a lack of sleep, also consider that people who are sleep deprived tend to eat more junk food – which only adds to their risk for cardiovascular disease
    • “The single greatest tool in my arsenal to eat well is to sleep well” – Peter
    • AND people who are sleep deprived will have out if whack insulin/glucose levels (they have hyperinsulinemia) – only worsening the problem
  • One study found that for people who were underslept (<6 hours/night of sleep) on a weight loss diet, 70% of the weight loss came from lean muscle mass and not fat
    • “Your body will ruthlessly hold onto its fat when you are underslept”

A Lack of Sleep is a Reproductive Nightmare

  • Men who are sleeping 5-6 hours/night will have a level of testosterone that of 10 years their senior
    • This also works against fat loss
    • Related:
      • Men sleeping 5 hours a night have significantly smaller testicles than those sleeping 7 hours or more
      • Men sleeping 6 hours or less have fewer sperm – those sperm also have more genetic deformities and reduced motility
  • Women sleeping 5-6 hours/night show a 20% reduction in follicle stimulating hormone (FSH) – a critical hormone for getting pregnant
    • They also show a 30% higher rate of abnormal menstrual cycles

Can’t you just catch up on sleep on the weekends?

  • “Human beings are the only species that deliberately deprive themselves of sleep for no apparent reason”
    • Except:
      • When a new mother cares for her young
      • Under conditions of starvation – there’s a biological mechanism in place which acts to keep the animal awake longer so they can find more food
    • “Mother nature has never had to face the challenge of sleep deprivation”
      • Faced with famine, we evolved fat cells – allowing us to store food and then use the fuel as needed
      • Perhaps over a long enough time scale, we’ll be able to store sleep credit
        • But right now – Sleep isn’t like the bank, you can’t accumulate sleep debt during the week and sleep it off on the weekends
          • Waking up 6-7 AM Monday through Friday and sleeping in on the weekends until 10-11 AM on Saturday/Sunday, and then forcing yourself to get to bed at a reasonable hour come Sunday night for work Monday morning is no different than flying back and forth from SF to NY every weekend
    • “When you fight biology…like sleep, you normally lose. And the way you know you’ve lost is disease and sickness.”
      • “At some point a lack of sleep will get you”

How a Lack of Sleep Wrecks the Immune System

  • There are links between a lack of sleep and cancer of a variety of forms
    • Bowel cancer, prostate cancer, and breast cancer
  • The World Health Organization recently classified nighttime shift work as a probable carcinogen
  • Adults limited to just 4 hours of sleep for only one night experienced a 70% drop in natural killer cell activity
    • Natural killer cells are responsible for identifying and destroying  malignant cancer cells
    • Now imagine after months of insufficient sleep…
  • “Sleep is one of the most powerful regulators of your immune system”
    • And the scary thing is, as we age – sleep quality declines
  • One study injected mice with cancer cells
    • Compared to mice who were allowed to sleep as needed, those mice with restricted sleep had tumors 200% greater in size

The Lack of Sleep People Get in Medical School

  • Most doctors in medical school only get 1-2 hours of sleep-related training
    • (1-2 hours regarding a third of their patient’s lives…)
  • In Peter’s medical school residency, he recalls how he was on call every third night (and on those nights, he routinely got <5 hours sleep – he estimates he averaged 2-3 hours)
    • Peter actually recalls falling asleep while performing an operation on a patient during med school due to sleep deprivation
  • If an attending surgeon has slept only 6 hours in the previous 24 hour period, there is a 170% higher likelihood that they’ll make a major surgical error
  • If a med school resident works a 30-hour shift (compared to a 16-hour shift), that resident has a 178% increased chance of getting in a car crash after their shift
  • 1 in 5 medical residents will make a serious medical error during their residency caused by insufficient sleep
    • 1 in 20 will kill a patient (there are about 20,000 medical school residents active right now)

The Problem with Early School Start Times

  • “We will look back in probably 20 years with shame that we were having schools start at 7:30 in the morning”
    • For schools that start this early, buses often begin their rounds around 5:30 AM – meaning some kids have to wake up as early as 5 AM
  • When school start times are pushed back:
    • Grades and SAT scores improve
    • Truancy rates decrease
    • Behavioral and psychiatric problems decrease
    • The number of people who drop out of school (and certain classes) decreases
    • The life expectancy of students increases
      • Why? – There’s a reduction in car crashes in students aged 16-18 
        • One study in Wyoming found that delaying a certain school’s start time from 7:35 AM to 8:55 AM dropped accidents by 70% (compare this to the invention of anti-lock brake systems which dropped the accident rate by 20-25%)
  • “When sleep is abundant minds will flourish. If our goal as educators truly is to educate and not risk lives in the process then I fear we are failing our children in a spectacular manner with this incessant model of early school start times.”
  • Why are early school start times harmful? 
    • Kids aged 16-18 still need 9-10 hours of sleep (our brains don’t really stop developing until we’re about 25)
      • Only 11% of 18-year-olds are getting sufficient sleep (most only get ~7 hours)
    • The circadian rhythm of teens is wired to have them go to bed and wake up later (it’s shifted forward compared to adults)
      • Kids aged 16-18 tend to have chronotypes wiring them to sleep from 10 PM – 12 AM to 8:30-10:30 AM
  • Related – 72% of parents think their teen is getting the sleep they need, but as mentioned, only ~11% actually are
  • Some history:
    • Back in the 1960s or so, schools tended to start around 9 AM
    • As society marched on in terms of development, the start times were pushed earlier and earlier
  • Matt thinks a 10 AM start time is the sweet spot
    • If we went this route, perhaps hold school end times constant and just get rid of summer vacation

How can parents help kids get the sleep they need? (and things adults can do as well)

  • EXCISE TECHNOLOGY
    • “Taking that technology out of the bedroom is probably the single best thing you can try do”
    • Same for adults – “We are a dark deprived society in this modern era”
      • We need darkness at night to allow for the release of a hormone called melatonin (which helps time the onset of sleep)
        • Using an iPad for an hour before bed causes a 50% drop in the melatonin that’s released AND that melatonin peak will be delayed by 3 hours
        • An hour of iPad use before bed also reduces the amount of REM sleep you’ll get
    • Stop watching TV in bed
      • This allows your brain to create an association of being awake in bed which can lead to insomnia
    • 80% of teens admit to waking up in the middle of the night to check their phones
    • Even if you put your phone in airplane mode, there’s the issue of anticipatory anxiety
      • This is similar to when you have to wake up extra early to catch a flight and you set an alarm, but you wake up 1-2 minutes before the alarm
      • The first thing people do when they wake up is check their phone, unlocking a world of anxiety which comes flooding in
        • By doing this, you’re training your brain to anticipate that anxiety every morning
          • Why does this matter? – This anticipation reduces the amount of deep sleep you get

What about reading in bed?

  • Read in a different room, and then go to bed
    • Otherwise, the brain associates lying in bed with being awake
  • If you do read before bed, be mindful of the type of light you’re using
    • Avoid LEDs which are high in blue light (which inhibits melatonin release)
      • Red and yellow light is preferable in the evening

How long (and when) did we evolve to sleep?

  • The term “midnight” used to mean “middle of the night”
    • Now it’s when most people go to bed/check social media for the last time 
    • Compare this to current day hunter-gatherer tribes who tend to go to bed around 1.5-2 hours after sundown (8:30-9 PM)
      • They’ll get around 7-7.5 hours of sleep, and then take a siesta-like nap in the afternoon (bringing them up to a total of around 9 hours) – this is known as biphasic sleep

A Tip to Fight Insomnia

  • If you can’t fall asleep, get up and go read/watch TV in a different room
    • Lying in bed awake is the worst thing you can do
      • “You would never sit at a dinner table waiting to get hungry, so why do we lie in bed waiting to get sleepy?”

Naps

  • Naps have been found to benefit learning & memory, immune function, improve heart rate variability, and lower systolic blood pressure
    • You can nap for as few as 20 minutes and still see some mental benefits
    • But the ideal nap length is about 90 minutes – this gives the brain the ability to go through the full 90-minute sleep cycle (check out the Podcast Notes from Part I of this interview for more on this)
  • If you’re finding it difficult to fall asleep at night, do NOT nap during the day
    • From the moment we wake up in the morning, a chemical called adenosine builds up in the brain
      • The more it builds up, the sleepier you’ll feel
      • After about 16 hours of accumulation, you should have enough adenosine built up allow you to fall/stay asleep easily
        • During sleep, the brain clears away the adenosine
      • Naps remove some of this adenosine, thus reducing your overall sleep pressure

Let’s Dig Deeper on the Hormones

  • Adenosine, as mentioned, accumulates through the day and makes you sleepy
    • Caffeine acts to blunt this adenosine build up
  • Melatonin is the hormone that rises when it gets dark to signal to our body it’s time for bed
  • Cortisol (also known as the stress hormone) levels typically rise when you wake up – this allows you to be awake/alert throughout the day
    • As night comes on, cortisol needs to drop in order for you to initiate sleep
      • During the night cortisol drops further, and a few hours before you wake up, cortisol starts to rise again
    • People with insomnia often experience a cortisol spike right around bedtime – inhibiting sleep (aka sleep onset insomnia) (at this time, the sympathetic nervous system is activated – the fight or flight branch)
      • Sometimes cortisol will spike during the night when it should be dropping, causing sleep maintenance insomnia (aka difficulty staying asleep) (the sympathetic nervous system is activated)
      • As background, it’s helpful to stimulate the parasympathetic nervous system near bedtime (by doing things that relax you – like using a foam roller or meditating)
        • Meditation prior to bed has been shown to decrease the amount of time it takes someone to fall asleep (the continuity of sleep is also improved)
  • Glucose is correlated with cortisol
    • Peter has noticed that when his glucose levels are high at night, he tends to get poorer sleep

Sleeping Pills

  • The main sleeping pills (like Ambien and Lunesta) on the market now don’t stimulate restful/deep sleep
    • They’re also associated with a higher risk of death/cancer
    • Ambien is more of like a chemical baseball bat to the head that just makes you unconscious – it’s not “sleep”
  • Peter used to take Ambien in 2011-20012 to help him sleep on flights back in his consulting days
    • He remembers discovering several emails he doesn’t actually remember sending

Random Yet Useful

  • 2 hours before waking up we experience a drop in body temperature
  • Peter has noticed that 400-600 mg of phosphatidylserine helps stimulate sleep
    • It’s part of Peter’s jet lag protocol – discussed in these Podcast Notes

These notes were edited by RoRoPa Editing Services

Check out the Podcast Notes for Part III

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