Sleep is a really weird thing, when you think about it. Sometimes when I’m drifting off to sleep, I’ll find myself thinking, “There are tens of millions of people right now lying unconsciously in theirs beds, temporarily paralyzed and experiencing intense hallucinations.”
Because that’s what happens during sleep. It’s crazy, huh?
But why must we all engage in this nightly routine? For most of human history sleep has been a big mystery. It wasn’t until fairly recently that scientists have begun to understand why animals and humans need to sleep. And even those emerging ideas are just hypotheses. When Dr. William C. Dement, who founded the Sleep Research Center at Stanford University and has researched sleep for over 50 years, was asked why we need to sleep, his golden response was: “As far as I know, the only reason we need to sleep that is really, really solid is because we get sleepy.” So despite the ability to peer into the brain with advanced technologies like MRIs and EEGs, sleep remains almost as much of a mystery to us as it was for the ancients.
While we don’t know exactly why we need to sleep, we do know it provides a myriad of benefits, and that if we don’t get enough of it, we risk a plethora of health and mental problems. The funny/sad thing is, even though sleep is an important part of overall health, it doesn’t get the same attention as diet and exercise does. People rarely boast of their propensity for eating mass quantities of Cheetos, but folks love to offer humble-brags about how little sleep they’re getting by on; it’s become a badge of honor to show off how busy one is with more important things. Sleep has unfortunately become associated with laziness – a luxury for the non-go-getter set. Yet, if you Chezmoi Collection, Al... Buy New $37.02 (as of 07:40 EDT - Details) want to get bigger, stronger, leaner, and manlier, as well as smarter and more emotionally resilient, you’ll need to be as thoughtful about your sleep as you are about your deadlifting and paleo diet. Sleep is truly one of the most neglected parts of building a foundation for a life of excellence. In fact, the average human spends an astonishing 24 years of their life sleeping; you’d be wise to understand it and make sure you’re getting the most out of it.
In this post, we’re going to take you on an in-depth tour of the wonders of sleep. We’ve covered the art of napping before, so here we will be focusing on nighttime slumber. You’ll learn what happens while you sleep, the things that control your sleep, what happens when you don’t get the sleep you need, and the benefits of getting the right amount of sleep. Then, next week, we’ll cover the things you can do to create the best night’s sleep of your life.
Grab a glass of warm milk, put on your PJs, and let’s do this.
Understanding the Sleep Cycle
Before the 20th century, the common belief among scientists and doctors was that our brain basically shut down during sleep and the only parts that remained active were those essential for keeping us alive. However, with the invention of electroencephalography (EEG) and the ability to measure brain waves, that belief changed.
We now know that there are two major types of sleep: 1) Non-REM (quiet sleep) and 2) REM (dreaming sleep). These two cycles alternate with each other over the course of the night.
Non-REM (Quiet) Sleep
Non-REM sleep consists of four stages (or three, depending on who you ask):
- Stage 1: We’re technically not asleep during Stage 1, but we’re well on our way. We spend about 5 minutes in this phase, though it can last longer. Brain activity begins to slow down; body temperature starts to drop; muscles relax; eyes move slowly from side-to-side. During Stage 1 sleep we lose awareness of our surroundings but we’re still easily jarred to wakefulness. If you’ve ever woken up from a sleep but claimed you were just “resting your eyes,” you were likely roused during Stage 1.
- Stage 2: This is the first stage of honest-to-goodness sleep. The first time it occurs during the night, it lasts 10-25 minutes before you go to the next stage. During Stage 2 sleep, your eyes are usually still, and breathing and heart rate are slower than when you’re awake. Brain activity is irregular; the EEG will pick up intermediate-sized brain waves intermingled with bursts of fast activity.
- Stages 3 and 4: Stages 3 and 4 are typically smooshed together by researchers and are called “deep sleep” or “slow wave sleep.” Deep sleep lasts anywhere from 20 to 40 minutes, but declines with age. In this stage, brain activity primarily consists of large, slow waves. Breathing slows and blood pressure drops 20 to 30 percent below awake levels. You’re much less responsive to external stimuli during deep sleep and thus harder to rouse. It’s in this stage that our bodies also repair and renew themselves. At the beginning of deep sleep our pituitary gland releases a pulse of human growth hormone to help with tissue repair and growth. Levels of substances that activate our immune system, like interleukin, increase in our blood.
REM (Dreaming) Sleep Doctoru2019s Best Brai... Buy New $26.26 (as of 09:20 EDT - Details)
The 4 stages of sleep alternate with REM (Rapid Eye Movement) sleep, which is basically when your mind has a party. Here’s what happens to our body and mind during REM sleep:
- Brain releases a small amount of a substance called DMT which has intense psychedelic properties
- Brain activity skyrockets because we’re dreaming
- Muscles not needed for breathing or eye movement are paralyzed; we can’t move during REM sleep
- Eyes move back and forth rapidly (hence the name)
- Blood pressure increases
- Heart and breathing levels increase to daytime levels
- Testosterone levels increase
- Erections regularly occur in men
- Despite being paralyzed, our sympathetic nervous system is twice as active as when we’re awake
We typically experience three to five REM sessions a night. The first episode lasts just a few minutes, but REM sleep gets progressively longer as the night goes on. The final REM session can last up to an hour.
A normal sleeper moves between these two sleep patterns in a fairly predictable manner over the course of the night. If you were to get 8 hours of uninterrupted sleep, you’d go through four to five alternating non-REM and REM sessions. Above is a chart that shows a typical sleep cycle during 8 hours of sleep. Notice how REM and Stage 2 begin to alternate as the night progresses.