#126 – Matthew Walker, Ph.D.: Sleep and immune function, chronotypes, hygiene tips, and addressing questions about his book
Sleep expert Matthew Walker, Professor of Neuroscience and Psychology at UC Berkeley, discusses COVID-19's impact on sleep, including increased sleep duration and dreaming, and the critical link between sleep and immune function, especially for vaccine efficacy. He also shares essential sleep hygiene tips, explains sleep chronotypes, and addresses errors in his book, "Why We Sleep."
Deep Dive Analysis
12 Topic Outline
Introduction to Matthew Walker and Episode Topics
Impact of COVID-19 on Sleep: Amount, Timing, and Dreaming
Understanding Sleep Stages: Non-REM and REM Cycles
REM Sleep, Dreaming, and Emotional Processing
Alcohol's Negative Impact on Sleep Quality and REM Sleep
Sleep's Crucial Role in Immune Function and Vaccine Efficacy
Factors Determining Deep Sleep and REM Sleep Needs
The Double-Edged Sword of Napping and Hunter-Gatherer Sleep
Essential Sleep Hygiene Tips and Wind-Down Routines
Identifying and Understanding Sleep Chronotypes
Night Terrors in Children: Causes and Triggers
Addressing Errors and Interpretations in 'Why We Sleep'
7 Key Concepts
Social Jet Lag
This refers to the difference between the sleep one gets during the week versus the weekend. Typically, people sleep less during the week and then 'binge' on sleep during the weekend, which forces their biological clock to shift, similar to flying across time zones.
Non-Rapid Eye Movement (non-REM) Sleep
One of the two primary types of sleep, subdivided into four stages (one through four) that increase in depth. Stages three and four are considered deep sleep, while stages one and two are light non-REM sleep.
Rapid Eye Movement (REM) Sleep
The other main type of sleep, principally associated with vivid, narrative, emotionally filled, bizarre, and hallucinogenic dreaming. It is less determined by how long one has been awake and more by the circadian time of night.
Sleep Cycle Architecture
Humans experience a beautiful battle for brain domination between non-REM and REM sleep that plays out in approximately 90-minute cycles throughout the night. The first half of the night is dominated by deep non-REM sleep, while the second half is rich in REM sleep.
Adenosine
A chemical that builds up in the brain from the moment one wakes up, producing 'sleep pressure' or sleepiness. The longer one is awake, the more adenosine accumulates, leading to a greater drive for deep sleep.
Chronotype
An individual's innate preference for being a morning person (lark), an evening person (owl), or somewhere in between. It is strongly influenced by genetics and determines when one's peak alertness and sleepiness occur on a 24-hour clock face.
Sleep Procrastination
This occurs when individuals delay going to bed by engaging with technology or other activities, even when feeling sleepy. It can lead to later bedtimes and reduced sleep duration.
9 Questions Answered
The pandemic has impacted sleep in three main ways: increased total sleep time (by 15 minutes on average in Europe), decreased social jet lag (people sleeping more consistently), and increased dreaming due to later wake-up times and heightened emotional processing needs.
REM sleep acts as a form of 'overnight therapy' or 'emotional first aid,' helping the brain process and de-risk difficult emotional experiences. Increased emotional challenges, such as those during the pandemic, can trigger a homeostatic response for greater REM sleep.
Alcohol is a sedative that fragments sleep, stimulates the fight-or-flight nervous system, releases wake-promoting chemicals, and significantly decreases the amount of REM sleep, especially in the later hours of the night, thereby impairing emotional processing.
Insufficient sleep is linked to increased vulnerability to infections (e.g., common cold, pneumonia) and reduced immune response. Notably, getting insufficient sleep in the week before a flu shot can lead to less than 50% of the normal antibody response, suggesting sleep quality may impact COVID-19 vaccine effectiveness.
Deep sleep is primarily determined by the accumulation of adenosine (sleep pressure) from being awake, while REM sleep is more strongly determined by the circadian time of night, with more REM occurring in the second half of the sleep period.
Naps are a double-edged sword: they can offer learning and memory benefits even if short. However, if one struggles with nighttime sleep (insomnia), naps should be avoided as they reduce the healthy sleep pressure needed for solid nighttime sleep.
While genetic tests exist, a pencil-and-paper method called the MEQ (Morningness-Eveningness Questionnaire) test can provide a good estimation of one's chronotype. Knowing your chronotype can help explain struggles with societal work schedules, reduce self-blame, and inform lifestyle choices for better sleep harmony.
Night terrors, more common in children, typically involve waking with dread and fear from deep non-REM (dreamless) sleep. Exhaustion can trigger them because extended wakefulness leads to a homeostatic increase in the amount and intensity of deep sleep, thereby increasing the likelihood of a night terror.
Identified errors included misstating the number of individuals in studies, incorrect percentages (e.g., depression response to sleep deprivation), imprecise language (e.g., 'cardiac arrests' instead of 'cardiac events'), and lack of specificity (e.g., 'all forms of cancer' instead of 'specific forms of cancer').
15 Actionable Insights
1. Prioritize Sleep Before Vaccination
Ensure you get sufficient sleep in the week leading up to any vaccination (e.g., flu shot), as insufficient sleep can significantly reduce the antibody response, making the vaccine less effective. This principle may apply to future COVID-19 vaccinations as well.
2. Avoid Alcohol for Better Sleep
Minimize or avoid alcohol consumption, especially in the evenings, as it acts as a sedative that fragments sleep, stimulates the fight-or-flight system, and significantly decreases beneficial REM sleep. REM sleep is crucial for emotional processing and reducing anxiety.
3. Establish Regular Sleep Schedule
Go to bed and wake up at the same time every day, including weekends, to maintain a consistent circadian rhythm. This reduces ‘social jet lag’ and helps your body anticipate sleep, improving overall sleep quality and duration.
4. Create a Wind-Down Routine
Dedicate 15-30 minutes before bed to a relaxing routine, such as light stretches or meditation, and put away all electronic devices. Sleep is a gradual process, like landing a plane, and requires time to transition from wakefulness to stable sleep.
5. Optimize Bedroom Environment
Ensure your bedroom is dark and cool, as a lower body temperature is necessary for initiating sleep; it’s easier to sleep in a room that’s too cold than too hot. Remove all clock faces to prevent anxiety from checking the time if you’re awake.
6. Manage Naps Strategically
If you struggle with falling or staying asleep at night, avoid daytime naps to build up sufficient ‘sleep pressure’ (adenosine). However, if you sleep well at night, short naps can offer cognitive and cardiovascular benefits.
7. Get Morning Daylight Exposure
Expose yourself to daylight during the first half of the day. This is just as important as darkness at night for regulating your circadian rhythm and signaling to your brain that it’s time to be awake and alert.
8. Avoid Staying Awake in Bed
If you find yourself awake in bed for more than 20 minutes, get up and do something else until you feel sleepy again, then return to bed. This prevents your brain from forming a learned association between your bed and wakefulness/anxiety.
9. Keep Technology Out of Bedroom
Keep all electronic devices outside the bedroom to avoid ‘sleep procrastination’ and the flood of anxiety that comes from checking them. This also prevents anticipatory anxiety about waking up to information overload.
10. Delay Morning Phone Check
Avoid checking your phone immediately upon waking; instead, wait at least an hour. This prevents a ‘jag of anticipatory anxiety’ that can lighten your sleep throughout the night and sets a more positive tone for your day.
11. Understand Your Sleep Chronotype
Determine if you are a morning, evening, or intermediate type using the MEQ test (Morningness-Eveningness Questionnaire). Knowing your innate chronotype can help you align your schedule with your biology, reduce self-blame, and explain struggles with conventional work/school times.
12. Address Sleep Disorders First
If you suspect you have a sleep disorder like insomnia or sleep apnea, consult a doctor for diagnosis and intervention. Sleep hygiene tips alone will not be effective if an underlying medical condition is impairing your sleep.
13. Prevent Child Exhaustion for Terrors
For parents of children experiencing night terrors, ensure the child is well-rested and avoid situations that lead to exhaustion. Increased deep non-REM sleep due to extended wakefulness or missed naps can increase the likelihood of night terrors.
14. Seek Pediatric Sleep Expertise
For specific questions or issues regarding infant or child sleep, consult experts like Dr. Craig Canapari (Yale Medical School) or Dr. Jodi Mindell, who are leading authorities in pediatric sleep research and clinical practice.
15. Implement Incremental Habit Changes
When adopting new sleep habits, start with small, manageable goals and gradually increase the duration or intensity. This approach, inspired by behavioral change research, sets you up for success rather than failure.
4 Key Quotes
It's not time that heals all wounds. It's actually time during REM sleep and dreaming that provides this emotional convalescence.
Matthew Walker
When you fight biology, you normally lose. And the way you know you've lost is often through disease and sickness.
Matthew Walker
Sleep is much more like trying to land a plane. It takes time to gradually descend down onto that hard foundation of this thing that we call a stable night of sleep.
Matthew Walker
If you're going to have your phone in your bedroom, the rule is that you can only use it if you're standing up.
Michael Gradner (quoted by Matthew Walker)
3 Protocols
General Sleep Hygiene Tips
Matthew Walker- Maintain regularity by going to bed and waking up at the same time each day.
- Ensure lots of darkness at night to promote melatonin production.
- Get sufficient daylight exposure during the first half of the day to regulate circadian rhythm.
- Keep your bedroom cool, as you need to drop your core body temperature to initiate sleep.
- If you've been awake in bed for 20 minutes, get up and do something else, only returning to bed when sleepy to avoid associating the bed with wakefulness.
- Avoid alcohol and caffeine in the afternoon and evening.
Wind-Down Routine for Better Sleep
Matthew Walker- Give yourself a wind-down opportunity of 15-30 minutes before bed.
- Engage in relaxing activities like light stretches or meditation.
- Put away all phones and gadgets.
- Stay clear of any inbound information (emails, texts, social media) in the last 30 minutes before sleep.
Managing Phone Use in the Bedroom
Michael Gradner (quoted by Matthew Walker)- If you must have your phone in your bedroom, only use it while standing up.
- Once you feel the desire to sit down or get into bed after 5-10 minutes of phone use, put your phone away.