Episode Notes:
Sleep is an incredibly complicated process that plays an incredibly important role in recovery and human optimization. As a passive activity, it is much harder for us to assess our sleep performance and actively improve our sleep. Technology and research has helped clarify what actually happens during sleep, and the key mechanisms of different phases of sleep.
In this episode, we are going to explore why sleep is so important by understanding the components of the sleep cycle and factors that influence them. You’ll learn about the stages of the sleep cycle, the benefits of each stage, and potential disruptions that may be compromising your sleep. I’ll also share my experience with tracking my sleep stages and best practices for understanding, documenting, and adapting to your sleep tendencies.
Topics
[2:38] A breakdown of the different sleep stages
[5:58] Memory consolidation during N2 and REM sleep
[8:00] Steroid secretion during deep sleep
[9:05] The impact of your sleep schedule on restorative sleep
[10:12] Alcohol and cannabis: Implications for sleep
[13:13] Tracking my sleep: Observing trends in REM and deep sleep
[17:57] Top tips for you to understand and track your sleep
Thank you all for joining me on this journey to lifelong health, happiness, and higher performance. And remember, always be grateful, love yourself, and serve others.
Teaser
In this episode… synaptic connections that were stressed throughout the day via neuroplasticity are strengthened. Additionally, the sleep activates the glymphatic system in the brain which flushes out excess cellular and metabolic waste that has accumulated in the brain…
Episode Intro
Learn II Perform: Practical lessons so that you can immediately learn to optimize your health, happiness, and performance.
Gratitude
As always, I like to start off each episode with an expression of gratitude to someone or something that has really improved my life. Today, I would like to give thanks to a special device that I hold dear to my heart – my WHOOP fitness tracker [2]. WHOOP offers an incredibly comprehensive analytics platform that tracks critical physiological metrics, including heart rate variability, resting heart rate, sleep performance, cardiovascular strain, and recovery. Learning how my body responds to different stressors and lifestyle factors is crucial to optimizing my life, and the WHOOP tracker is my go-to resource to check in with my health and largely influences many of my lifestyle choices. So today, and every day, I’m grateful for Will Ahmed and his team at WHOOP for creating great technology and resources to help people improve their lives.
Topic Introduction
“Scientists have discovered a revolutionary new treatment that makes you live longer. It enhances your memory and makes you more creative. It makes you look more attractive. It keeps you slim and lowers food cravings. It protects you from cancer and dementia. It wards off colds and the flu. It lowers your risk of heart attacks and stroke, not to mention diabetes. You’ll even feel happier, less depressed, and less anxious. Are you interested?” [1]
Of course, that brilliant excerpt, from Dr. Matthew Walker’s book, Why We Sleep, is all about sleep. In episode five, we discussed the circadian rhythm and dangers of sleep deprivation, meanwhile, this episode will continue our review of the more than 17,000 well-documented scientific reports favoring the benefits of sleep by focusing on the sleep cycle and modes of recovery [1]. One way to think of sleep, is that sleeping for enhanced performance is akin to taking steroids for muscle gain. But that’s literally true, because sleep actually produces steroids for muscle gain, as we’ll find out. For me, sleep is now a non-negotiable priority in my life and you’re going to discover why.
So What’s the Bottom Line
Sleep is possibly the best recovery mechanism and contributor to complete human optimization. In this sleep overview, we are going to explore why sleep is so important by understanding the components of the sleep cycle and factors that influence them. We will address three main topics:
1. The Sleep Cycle: How it works
2. Benefits and Functions of each sleep stage
3. Disruptions to the sleep cycle
1. The Sleep Cycle: How it works
While scientists are still working to understand the complex mechanisms of sleep, this is what we know. Sleep is typically divided into two main categories, non-Rapid Eye Movement, or non-REM (NREM) sleep, and rapid eye movement, or REM sleep [3, 4, 5]. Let’s start with NREM.
NREM is typically divided into three categories, N1, N2, and N3, although the third category is sometimes split into two sub-categories. For our purposes, let’s stick with the three. During the NREM portion of a sleep cycle, the body progresses sequentially from stage one, N1, to stage two, N2, and finally stage 3, N3. N1 is the lightest stage of sleep, often seen as the transition from wakefulness to a more relaxed brain stage. This transition stage often lasts 1-7 minutes and features alpha brain waves with frequencies between 8 and 13 Hz, and should only encompass up to 5% of your total sleep. It is during this time that you may be easily disrupted by sounds [5]. So if you find yourself trying to fall asleep and are easily awoken, you very well may have been in stage one.
Moving on, N2 sleep features reduced muscle activity and more stimulus is required to wake up. Quieter sounds or movements may not wake you, but a loud noise would likely be enough to bring you back to wakefulness. In this stage, the brain waves observed are typically theta waves, with frequencies between 4 and 7 Hz. This stage two sleep is typically distinguished by sleep spindles and K-complexes, which are essentially short bursts of higher frequency and negative high-voltage brain signals [6]. When tracking brain waves, you would be able to observe these spikes in brain activity. During the first sleep cycle, the duration of stage two sleep is typically 10-25 minutes but it increases with each sleep cycle throughout the night. In the end, this N2 sleep usually accounts for the largest portion of the night, averaging 45-55% of your total sleep [5].
N3 sleep is what we know as deep sleep, also referred to as slow-wave sleep, or SWS. As you may expect, brain waves slow down even further, characterized as delta waves with frequencies between 0.5 and 4 Hz [3]. In this stage, you become completely unaware of your surroundings and if woken up, you would likely be very groggy. To be forcefully woken up from this state, you would typically need at least 30 minutes to return to normal wakefulness. It is for this reason that there are now smart alarms that detect your sleep waves and wait to wake you up until after your stage three has passed, which I’ll discuss later. During this stage of deep sleep, your respiratory rate, heart rate, temperature, blood pressure and neural activity are all at their lowest. An interesting note, unlike N2 sleep which increases in length as the night goes on, the majority of your stage three deep sleep actually occurs in the first third of the night, typically reaching a total of 15-20% of your overall sleep [5].
And that brings us to the widely discussed REM sleep – associated with highest rates of dreaming, brain activity, and of course, the random movement of the eyes. Slow alpha waves are observed and like the N2 stage of sleep, the duration of each REM period increases as the night goes on [5]. Therefore, it is important to have a complete sleep to achieve sufficient REM activity throughout the night. Ideally, REM sleep in adults usually accounts for 20-25% of total sleep.
So to recap this section, NREM is divided into three phases, N1 being the transition from awake to light sleep, N2 being the primary time spent in light sleep, and N3 being the deep-sleep phase. Finally, our cycle concludes with REM sleep, noted for dreaming and large amounts of brain activity.
2. Benefits and Functions of each sleep stage
There has long been an association between stage two light sleep and memory consolidation, evidenced by a 2002 study that observed a higher prevalence of sleep spindles, which are associated with stage two sleep, after subjects were forced to learn a new task [7]. University of California, Berkeley professor of neuroscience and psychology Dr. Matthew Walker concluded in his excellent book, Why We Sleep, that most memory is associated with NREM sleep, particularly in the early stages of the night [1]. In studies on the ability to learn new facts, either after a full 8-hours of sleep or an all-nighter with zero sleep, he observed a substantial 40% improvement in learning and information retention [8]. As he eloquently puts into context in a TED talk, a 40% difference on a test is the difference between getting an A+ and failing. Pretty amazing stuff.
Now in terms of memory consolidation, there is also a wide body of research that has linked memory consolidation and neural healing mechanisms to REM sleep [5, 9, 10]. It appears as though the brain may replay short-term memories from the day and convert them into long-term memory storage while sleeping. Harpreet Rai, the founder of OURA ring, actually claims there is evidence from brain scanners that this replaying of short-term memories occurs at three times the normal speed [10]. So at this point, we now have evidence that memory consolidation primarily occurs in during the N2 and REM stages of sleep. For this reason, it Dr. Walker believes that naps can be very effective on cognitively demanding days because they predominantly entail the N2 stage of sleep associated with memory consolidation [1].
In addition to the cognitive performance benefits of sleep, there are distinct healing mechanisms that promote improved health, performance and disease prevention. During the different stages of sleep, synaptic connections that were stressed throughout the day via neuroplasticity – a topic covered in episode four – are strengthened. Additionally, the sleep activates the glymphatic system in the brain which flushes out excess cellular and metabolic waste that has accumulated in the brain throughout the day [3, 11, 12]. This cleansing system is very comparable to the lymphatic system of the immune system that flushes out toxins and damaged cells [3]. These processes not only help to improve cognitive function, but they can also help prevent neurodegenerative disorders such as Alzheimer’s, brain fog, and depression.
Moving from the brain to the rest of the body, it has been repeatedly reported that sleep is the best and most prevalent source of growth hormone and testosterone [3. 13-15]. For obvious reasons, this should be of extreme importance for athletes and fitness enthusiasts who look to build and repair skeletal tissue, but sufficient levels of these hormones are necessary for hormonal balances, reproductive health, and for that matter, overall health. So, while some people are actively taking steroids to increase performance, it should be noted that you literally have the ability to produce steroids on your own – 100% natural. The key is to get quality and sufficient sleep.
Emily Capodilupo, the director of Analytics at WHOOP, noted on a WHOOP podcast (episode 14 for those interested) that 95% of growth hormone is produced during the slow-wave, deep sleep [16]. Therefore, if you have a hard workout or stress the body, it is imperative to get appropriate sleep to recover and make gains. Missing out on sleep the night following a hard workout may essentially eliminate all of the potential gains… the window of opportunity for recovery is finite. Harpreet Rai, OURA’s founder, reminds us that gains aren’t made in the gym, they are made when you are sleeping [10].
3. Disruptions to the sleep cycle
Having reviewed the sleep cycle and its functions, there are a few potential disruptions to consider. As we learned, most NREM deep sleep happens early in the night and most REM sleep later in the night. However, Dr. Walker notes that these tendencies are associated with your circadian rhythm, not simply just the time from the start to end of your sleep [1].
To make sense of this, let’s pretend that you typically sleep eight hours from 10pm to 6am. If one day you wake up two hours earlier but going to bed at the same time, sleeping from 10pm to 4am, you have reduced your total sleep by 25%. But it is not exactly that simple. Because most of your REM sleep takes place in the last two hours of your sleep cycle and your sleep cycle is governed by your circadian clock, instead of reducing your REM sleep by 25% as well, you will have likely reduced it by60-90%! Alternatively, if you go to bed later, sleeping from midnight to 6am, you can expect to experience your typical REM sleep but will significantly reduce your deep sleep. Again, this is because the majority of deep sleep happens in the first third of the night. From this, we can see how inconsistent sleep and wake times may impact our sleep cycle. For more on circadian rhythms and sleep, I strongly encourage you to check out episode five.
Perhaps one of the most important and common disruptions to our sleep cycles is alcohol. In studies observing high dose alcohol consumption, evidence suggests that the second-half of the night features frequent disruptions as the body works to remove alcohol, referred to as a ‘rebounding effect.’ These disruptions often result in a suppression of REM sleep [17]. As Emily Capodilupo explains on episode 43 of the WHOOP podcast, alcohol is notorious for disproportionately reducing REM sleep [18]. By missing out on the first big REM period and a significant amount of slow-wave sleep, the majority of sleep experienced after alcohol consumption is light sleep. As a result, despite falling asleep easily and sleeping for long periods of time after alcohol consumption, the deep, restorative benefits of sleep are largely muted by alcohol.
For this reason, recovery after significant alcohol consumption is drastically reduced, as shown by a comprehensive study conducted by WHOOP with college athletes. WHOOP’s recovery metrics, which are based on sleep, heart-rate variability, resting heart rate, and a few other variables, found that reduced overall recovery was observed in 74% of athletes one day after alcohol consumption. 29% of athletes saw reduced recovery after two days, 19% after three days, and finally 7% of athletes still had decreased recovery after four and five days [19, 20]. Think about that for a second, one night of drinking has the ability to mitigate the body’s ability to properly recover for up to five days. This leads to the assumption that alcohol’s influence on sleep quality is a key contributor to compromised recovery.
Now, let’s talk about cannabis. Many people claim that cannabis significantly improves their sleep, and for people with medical disorders, this may be the case. Respected sleep specialist Dr. Michael Breus states that for those with obstructive sleep apnea, the THC found in cannabis has sedative effects that may improve breathing during sleep, potentially serving to decrease sleep latency [21]. However, he also notes that “THC-rich strains are likely to reduce levels of REM sleep.” In fact, a 2004 study found that THC impaired memory, despite increasing sleepiness and reducing the total time needed to fall asleep [22]. Further, a 2014 review of multiple human studies concluded that “cannabis is typically not beneficial to sleep except among medicinal cannabis users who are identified by the presence of pre-existing sleep interrupting symptoms such as pain” [23]. This conclusion was founded in the idea that cannabis, similar to alcohol, may increase light sleep to counteract for lost deep sleep. This is why the amount of time spent sleeping and the subjective quality of sleep may actually be misleading.
The final disruption I want to discuss is sleep apnea. Studies show that sleep apnea most commonly occurs in individuals who don’t have fully developed jaws. In this scenario, when the body enters deep, restorative sleep, muscles go limp and the tongue falls back, restricting breathing and preventing oxygen flow [24]. When the airway is restricted, sleep is frequently interrupted, preventing the individual from achieving the deep sleep necessary for restorative recovery [25]. It is suggested that snoring, turning, and sleep-talking could all be signs that the body is trying to reopen the pathway. It should also be noted that sleep apnea is particularly concerning for kids because their brain’s development have substantial oxygen needs [3].
Personal Experience
So with that, I’d like to share a little bit about my personal journey to understanding and optimizing my sleep. In doing so, I have looked to capitalize on technology for quantifiable feedback on lifestyle habits and sleep performance. I initially tried the WHOOP fitness tracker during my first full season of pro hockey, and then ended my subscription because my income was pretty much non-existent. Wanting to return to using WHOOP, I re-activated my membership in the summer of 2020 and have been diligently tracking my sleep and many more metrics.
Going back to the sleep cycles, we know that physical recovery is generally associated with stage three deep sleep and mental recovery is often associated with REM sleep. In support of this, I actually observed indications of this through my personal WHOOP data. During the summer months, I was committed to non-stop daily learning, studying four languages (at times studying over an hour a day of each), learning two instruments, and reading for a couple hours every day. On these highly cognitively-demanding days, I actually observed that my REM sleep the following night would increase significantly.
And this makes sense, because my brain had to work harder to consolidate memories from the day and generate long-term memory. Meanwhile, on days in which I performed high intensity exercise – running hill sprints or doing extended HIIT workouts – I observed an increase in deep sleep from my baseline. Now, obviously, as just one person, my personal experiences are a very small sample size and subject to many other variables. However, I continue to notice a trend of more REM sleep following cognitively demanding days and more deep sleep following physically demanding days. In addition, I have also clearly observed a greater amount of slow wave, deep sleep occurring in the first third and the first half of my nights, with an increased amount of REM sleep occurring in the last third of the night, as explained by Dr. Matthew Walker.
In addition to tracking my sleep, I frequently also implement naps in the early afternoon as a way of optimizing memory consolidation and recharge the brain for additional learning. Since I wake up at 5am, I have usually already been doing cognitively-demanding tasks for many hours by the early afternoon. When feeling as though my focus and alertness begins to wane, I like to lie down for a nap and completely refresh. I have no data to back this up, but I feel that separating my day in half allows for improved memory and learning. And, given the science, it is definitely possible that this is indeed the case.
Something interesting that I don’t quite have an answer for, is the increased REM that I experienced after my first evening whole-body cryotherapy session. On Monday, August 24th, 2020, I went for a 7pm whole-body cryotherapy session at Effect Therapy in Lethbridge [26]. This was just my second time doing whole-body cryotherapy, and my first time doing it in the evening. Amazingly, I observed a massive increase in REM sleep that night. In the two weeks prior, I averaged one hour and 23 minutes of REM sleep a night. However, that night, I experienced an enormous 2 hours and 51 minutes of REM sleep, over twice as much as my baseline, despite only spending 52 mins more time in bed than my average. To me, this was pretty incredible, and I share will share my WHOOP data in the show notes on the website. Interestingly, I did not notice significant repeated increases in REM sleep with future cryotherapy treatments, although I did enjoy subjectively good sleeps.
Now, to attempt to explain it, there are claims from some cryotherapy companies that whole-body cryotherapy increase levels of norepinephrine which help to regulate the sleep/wake cycle and promote REM sleep [27, 28]. Research I found confirms that whole-body cryotherapy increases levels of norepinephrine, and it has even been shown to lead to large spikes after initial treatments that subside as the body adapts, which is consistent with my experience, because I had the greatest reaction after my first evening cryotherapy sessions, but less of a reaction in following sessions [29, 30]. However, most studies show that norepinephrine is linked to wakefulness, and is therefore actually linked to REM suppression [31]. To be completely honest, I am stumped about how the rise in norepinephrine could be responsible for improved REM sleep, and is a subject that I’m going to have to explore further. But alas, the bottom line is that after cryotherapy, I have enjoyed great sleeps and in that first experience, my REM sleep was off the charts.
Moving on, the last point worth mentioning is disruptions. I have consumed very little alcohol in my life and believe that is a contributor to healthy sleep that I experience. Beyond my poor physiological response to alcohol, which I actually have genetic variants that result in alcohol flushing, and an overall lack of enjoyment of drinking, I have a really hard time justifying the consequences that come with drinking. However, in the spirit of science, I might just have to throw back some shots of tequila a few times so that I can observe alterations in my sleep cycles, but we’ll save that for another time. Moving on to cannabis, I have never taken any form of cannabis, so I have no experience with that and my sleep. As for sleep apnea, I have no reason to believe that apnea affects me, and after a month of mouth-taping to ensure nasal breathing during the night, I did not observe any noteworthy changes in sleep disturbances or sleep efficiency, so until I conduct further testing, I can conclude that I do get quality sleep. Again, I believe that keeping a very clean, natural, and healthy diet and lifestyle is an important part of optimizing my sleep and in turn, optimizing my life.
So What Can You Do
This brings us to the most important part of the show. By this time, I hope that it should be pretty obvious that sleep is important. As Harpreet Rai points out, we don’t exercise every day, but 99.9% of us sleep every night [10]. Further, he points out that we don’t get stronger in the gym, but rather, we get stronger in our sleep. Therefore, the first step to optimizing our lives should be to optimize our sleep. To do that, we need to make it a priority. You’re going to spend about a third of your life sleeping, you might as well make it count.
Managing sleep cycles can be a tricky task because it is a passive activity. However, I do have some recommendations for how you can begin to better understand and optimize your sleep cycles.
1. Track your sleep
Using a fitness device to track your sleep can be an awesome way to learn about your sleep tendencies and discover how lifestyle factors impact your sleep. This doesn’t need to be a permanent task, but think of it is a chance to calibrate your lifestyle to your sleep. WHOOP and OURA are highly recommended fitness trackers, and as you can probably tell, I am in love with my WHOOP device. However, if you’re not looking for an expensive fitness tracker, there are many other options on the market and apps that may be able to provide valuable insights as well.
2. Try to maintain consistent sleep and wake times
By going to bed or waking up a few hours earlier or later than usual, you may be significantly altering your quantity of deep sleep and REM sleep.
3. Be conscientious of the effects of alcohol and cannabis
Doing what you enjoy is an important part of your psychological health, so this is a personal choice, but to optimize your sleep and your life, you should always be aware of the potential consequences of substance use. Recall that alcohol has been shown to impair recovery for up to five days, meanwhile data on cannabis is still largely inconclusive.
4. Try using a sleep tracker alarm
Sleep Cycle is an app that not only tracks your sleep, but it also wakes you up during a phase of light sleep to prevent those groggy mornings [31]. If you find yourself frequently having a hard time waking up, this may be able to help you out.
To close out, a quote from Nobel Prize winning Author of The Grapes of Wrath, East of Eden and Of Mice and Men, John Steinbeck. He said “It is a common experience that a problem difficult at night is resolved in the morning after the committee of sleep has worked on it” [32].
Episode Outro
To discover more, the full transcript of this episode with all citations is available on the website and you can also contact me on social media with any questions or comments. If you found this episode useful or think that it may help someone else, I encourage you to pass it along.
Thank you all for joining me on this journey to lifelong health, happiness, and higher performance. And remember, always be grateful, love yourself, and serve others.
References
[1] Walker, M. (2017). Why we sleep : unlocking the power of sleep and dreams. New York, NY: Scribner, an imprint of Simon & Schuster, Inc.
