peter attia paul grewal covid-19

Matthew Walker, Ph.D.: Sleep and Immune Function, Chronotypes, Hygiene Tips, and Addressing Questions About His Book| The Drive with Peter Attia #126

Key Takeaways

  • The pandemic brought about changes in the amount of sleep, timing of sleep, and dreaming
  • “It’s not time that heals all wounds, it’s the time during REM sleep and dreaming that provides emotional convalescence.” – Matthew Walker
  • Our brain will respond to events throughout the day and give us increases in non-REM or REM sleep depending on what we need
  • If you’re not getting enough sleep in the week prior to getting a flu shot, you produce less than 50% of normal antibody response and dull efficacy of a vaccine
  • There are pros and cons to napping but if you struggle with sleep at night, avoid taking naps throughout the day
  • Sleep is not a light switch, have a wind-down routine to rest the brain and body


Matthew Walker, Ph.D. (@sleepdiplomat) is a sleep expert and Professor of Neuroscience and Psychology at the University of California, Berkeley, USA. He is also the founder and director of the Center for Human Sleep Science.

In this episode of The Drive, Matthew Walker and Peter Attia discuss sleep chronotypes, how COVID-19 has impacted sleep, the importance of sleep for immune function and emotional health, sleep hygiene tips, and the pros and cons of napping.

Book: Why We Sleep by Matthew Walker, PhD

Host: Peter Attia (@PeterAttiaMD)

Sleep Cycles

  • Humans and mammals have two principle types of sleep: non-rapid eye movement (REM) sleep and REM sleep
  • Non-REM sleep is subdivided into four stages (stages 1-4)
  • Non-REM sleep stages increase in depth of sleep so stages 1 and 2 are light sleep, stages 3 and 4 are the deepest sleep
  • REM sleep is associated with dreaming
  • In humans, non-REM and REM generally cycle in 90-minute intervals throughout the night
  • The ratio of non-REM to REM within each 90-minute cycle changes
  • For reasons we don’t know, the majority of deeper sleep (stages 3 and 4) occurs in the first half of the night
  • In the second half of the night, the brain wants to consume more REM sleep
  • Increased cortisol negatively impacts deep sleep
  • From the moment we wake up, adenosine is released throughout the day and produces “sleep pressure” AKA sleepiness to aid deep sleep at night
  • More adenosine = more deep sleep

Sleep Chronotype

  • Some people naturally go to bed earlier and wake up earlier while others go to bed later and wake up later
  • 25-30% of the population are morning people, 25-30% are night owls, and the remainder are somewhere in between  
  • We might shift chronotype based on social schedule, work schedule, etc.
  • There is genetic basis and significant heritability to our chronotype
  • A collection of genes determine chronotype – most are clock genes and control rhythm of circadian cycle
  • Regardless of chronotype, innate rhythm will change as you progress through lifecycles
  • There are genetic tests to determine chronotype but there’s a simple, five-minute pencil and paper method called the Morningness-Eveningness Questionnaire (MEQ)
  • The MEQ has been validated against genetic tests

Would Knowing Our Chronotype Provide Benefit?

  • When you fight biology, you lose
  • Knowing your chronotype can explain insomnia and other sleep disorders that may be incorrectly diagnosed because we’re simply on a schedule that’s discordant with our body
  • It helps to understand where you are on the spectrum to provide some comfort that it’s genetic and not just that you’re lazy or don’t want to exercise in the morning, etc.
  • Partners can be more understanding of each other’s sleep schedules without blame
  • Children would likely do better with later school times if schedules can be selected
  • For more information on sleep in children, see:
    • Dr. Craig Canipari, MD, Director of Yale Pediatric Sleep Center and author of It’s Never Too Late to Sleep Train

Pros and Cons of Napping

  • Somewhere between 2-4 pm there’s a drop in physiological alertness – we’re almost pre-programmed as a species 
  • Pros: naps as short as 17 minutes can produce learning and memory benefits
  • Downside: it can take away sleepiness at night
  • “If you struggle with sleep at night, avoid naps during the day.” – Matthew Walker  
  • Sleep restriction therapy: stay awake longer and shoot for improved quality even if the length of time of sleep is slightly reduced  
  • If you are not struggling with sleep and napping fine during the day, naps are advisable

Sleep Hygiene Tips

  • Regularity: go to bed at the same time, wake up at the same time
  • Lighting: sleep in the dark, wake up to the light
  • Temperature: cool temperatures will help you sleep
  • Don’t lie in bed awake, that triggers the brain to think you should be awake and instills a learned association
  • Avoid alcohol and caffeine later in the day, as much as possible
  • Sleep is not a light switch, have a wind-down routine to rest the brain and body
  • If you have trouble sleeping, remove clockfaces from the bedroom – it doesn’t help to know that it’s 2 am and you’re still not asleep
  • Keep technology outside of the bedroom and don’t make it the first thing you do in the morning
  • Checking your phone right when you wake up trains your brain that anxiety/stress is coming to you as soon as you wake up and lightens your sleep throughout the night
  • If you must have your phone in the bedroom, make a rule that you can only use it while you’re standing up
  • Don’t try to change it all at once – start with something manageable: maybe wait five minutes before checking your phone in the morning, then ten minutes, then after you shower, etc.
  • Important note: none of these tips help if you have a diagnosable sleeping disorder (e.g., insomnia)

Alcohol and Sleep

  • Sleep is more fragmented because alcohol stimulates the fight or flight branch of the nervous system
  • Breathing is shallower during sleep after drinking
  • Alcohol decreases REM sleep
  • If you are not getting enough REM, you may not get emotional restorative benefits then end up drinking again the next day as a result, and the cycle continues
  • Alcohol metabolism is not the same in everyone; some sleep perfectly fine especially if alcohol is consumed early enough before sleep

Impact of COVID-19 Pandemic on Sleep

  • The pandemic brought about changes in the amount of sleep, timing of sleep, and dreaming
  • Amount: according to early studies, total sleep time during pandemic has increased across the country
  • Opportunity for sleep expanded during the weekdays
  • In the earliest stages of the pandemic, people were sleeping and going to bed on weekdays at times more similar weekend patterns
  • Quality: people reported worse quality of sleep, based on self-report
  • It’s likely the story will be more complex longitudinally
  • We may see two pools of people: those who are sleeping more because they do not have to commute versus those who are sleeping much worse because of stress and anxiety
  • There is a seasonal shift in sleep patterns as long as there’s sufficient exposure to light – but changes now are more drastic than usual

Why Has Dreaming Increased As A Consequence Of COVID-19?

  • Possible reasons: timing of sleep
  • Generally during COVID, people are going to bed later and sleeping in later, so they’re sleeping further into REM window and the result is more dreams
  • Second reason: if sleep schedule didn’t change, you may be protectively dreaming more
  • REM sleep seems to provide “emotional first aid” – time we take concerns and traumatic events and REM sleep tries to dull experiences so we don’t feel as consumed by events the next day
  • “It’s not time that heals all wounds, it’s time during REM sleep and dreaming that provides emotional convalescence.” – Matthew Walker
  • We also know that sleep is responsive – if something happened that day that requires a specific type of sleep, our brain will respond accordingly with either more non-REM or REM sleep

Sleep’s Impact on Immunity

  • We don’t have data yet on the amount of sleep and vulnerability to COVID-19
  • There’s an association between sleep health and immune health
  • Individuals who report getting less than 7 hours of sleep per night are nearly 3 times more likely to contract rhinovirus (common cold)
  • Women who sleep 5 hours or less were 70% more likely to develop pneumonia
  • From animal studies, causal links were drawn between sleep deprivation and fatality from malaria
  • If you’re not getting enough sleep in the week prior to getting a flu shot, you produce less than 50% of normal antibody response and dull efficacy of the vaccine
  • It would behoove us to track sleep in relation to future COVID-19 vaccine and plan prospectively

Why We Sleep Discussion

  • There have been 13 errors in the book that will be corrected in a future edition of the book, examples are below:
  • Error 1: association between sleep and cardiovascular disease was 500,000
    • Should read: 474,684 individuals
  • Error 2: the introduction states that short sleep can double the risk of cancer but in actuality, short sleep doesn’t double the risk of all types of cancer and is not associated with every type of cancer
    • Should read: short sleep is associated with a doubling of the risk of certain types of cancer, such as ovarian and lung cancers
  • Error 3: incorrectly stated 30-40% of patients will receive benefit in a paradoxical study in which depressed patients are deprived of sleep for one night
    • Should read: 45%
  • Error 4: incorrectly stated number of participants in a study analyzed for cardiovascular disease and short sleep
    • Should read: 2,282 individuals analyzed instead of over 4,000
  • Error 5: sleep loss was associated with a risk of increased cardiac arrest
    • Should read: outcome measure was cardiac events, not cardiac arrests

Interpretive errors or misgivings

  • The study cited that sleep is good to a point but the relationship between sleep and mortality tapers off at about 9 hours per night
  • This led to the misinformation that long sleep is bad for you and associated with a faster death
  • The study artificially looked like long sleep was associated with a quicker death because patients were very ill
  • Sleep was likely protective, but patients were getting poor sleep
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