#58 – AMA with sleep expert, Matthew Walker, Ph.D.: Strategies for sleeping more, sleeping better, and avoiding things that are disrupting sleep
This AMA episode features Matthew Walker, Professor of Neuroscience and Psychology at Cal Berkeley, discussing practical ways to improve sleep. He answers listener questions on optimizing sleep duration, quality, consistency, and avoiding common disruptors like food, exercise, and electronics.
Deep Dive Analysis
7 Topic Outline
Introduction to AMA with Matthew Walker
Accuracy of Consumer Sleep Tracking Devices
Optimal Timing for Eating Before Bed
Impact of Exercise Timing on Sleep
Sleep Deprivation's Effect on Appetite and Hormones
The Vicious Cycle of Sleep Deprivation, Cortisol, and Anxiety
Components of an Effective Wind-Down Routine
3 Key Concepts
Sleep Tracker Accuracy
Consumer sleep tracking devices are generally good at determining if you are awake or asleep, and reasonably good at distinguishing between non-rapid eye movement (non-REM) and rapid eye movement (REM) sleep. However, they are less accurate at differentiating specific stages within non-REM sleep, such as light versus deep sleep. While absolute numbers may be flawed, the devices tend to be consistently errorful, meaning relative changes in your sleep patterns from your personal baseline are more reliable indicators of actual changes.
Sleep Deprivation and Appetite Hormones
When a person is sleep-deprived, their brain interprets this state as a starvation signal from an evolutionary perspective. This triggers an increase in the hunger-stimulating hormone ghrelin and a suppression of the satiety-signaling hormone leptin, leading to increased food cravings, greater food intake, and reduced satisfaction after eating.
Sleep Deprivation and Cortisol
Chronic sleep deprivation typically leads to chronically elevated levels of cortisol, a stress hormone. This hypercortisolemia can contribute to anxiety and makes it very difficult to achieve quality sleep, creating a negative feedback loop where poor sleep drives higher cortisol and anxiety, which in turn further impairs sleep.
5 Questions Answered
These devices are generally good at distinguishing between wake and sleep, and reasonably good at differentiating non-REM from REM sleep. However, they are less accurate at classifying specific sleep stages like light vs. deep non-REM sleep, but relative changes within an individual over time are often reliable indicators of sleep changes.
Yes, it's generally recommended to stop eating about three hours before bed to avoid acid reflux and digestive issues. Additionally, eating simple carbohydrates close to bedtime can slightly increase core body temperature, making it harder to fall asleep, as a drop in core body temperature is needed for sleep initiation.
Exercising within two hours of bedtime can be detrimental to sleep because it raises core body temperature, which counteracts the natural drop needed for sleep. It also releases stimulating hormones like epinephrine, norepinephrine, and cortisol, which can interfere with sleep onset.
Sleep deprivation causes the brain to perceive a starvation signal, leading to an increase in ghrelin (hunger hormone) and a decrease in leptin (satiety hormone). This results in increased food cravings, greater food intake, and reduced satisfaction, contributing to an obesogenic state.
Chronic sleep deprivation typically leads to elevated cortisol levels (hypercortisolemia). High cortisol can induce anxiety, which in turn makes it difficult to fall and stay asleep, creating a negative feedback loop where poor sleep exacerbates cortisol and anxiety, and vice versa.
7 Actionable Insights
1. Maintain Cooler Sleep Environment
Ensure your sleep environment is cooler rather than too hot, as you will always find it easier to fall asleep in a room that’s too cold than too hot. You need to drop your core body temperature by about two to three degrees Fahrenheit to initiate and stay asleep.
2. Stop Eating Three Hours Before Bed
Cease eating approximately three hours before bedtime to prevent acid reflux, digestive issues, and an increase in core body temperature from caloric burning, all of which make it harder to fall asleep.
3. Avoid Simple Carbs Before Bed
If you must eat closer to bedtime, avoid simple carbohydrates and lean more towards protein. Simple carbs are quickly translated into energy and heat, raising core body temperature and making it harder to fall asleep.
4. Exercise More Than Two Hours Before Sleep
Engage in exercise more than two hours before sleep, as it is a fantastic tool for sleep promotion. Avoid exercising within two hours of bedtime to prevent elevated core body temperature and the release of stimulating hormones like epinephrine, norepinephrine, and cortisol.
5. Prioritize Sleep for Exercise Performance
Prioritize getting good sleep, as it profoundly helps exercise performance and motivation. Adequate sleep increases motivation for physical activity, improves peak muscle strength, enhances respiration, decreases injury risk, and optimizes perspiration.
6. Remove Electronics Before Bed
Get electronics out of the way before bed because blue light from screens prevents the pineal gland from releasing melatonin, and the content can create emotional arousal, both hindering sleep.
7. Interpret Sleep Tracker Trends
When using sleep tracking devices, focus on weekly trend lines and relative changes from your personal baseline established over a few months, rather than worrying about daily absolute numbers. While daily readings may be inconsistently errorful, deviations from your trend line likely represent real changes in sleep patterns.
3 Key Quotes
Don't follow headlines, follow weekly trend lines.
Matthew Walker
Human beings seem to be the only species that will deliberately deprive themselves of sleep for no apparent reason.
Matthew Walker
I should put fangs on my phone.
Peter Attia