Sleep Cycles & What You Should Know About Them - By Henry Toraño

There’s few things more natural than sleeping. We knew how to sleep the day we were born. In all but very few cases, we’ve done it virtually every single day of our lives. Most humans spend nearly two thirds of their lives sleeping. What’s mind boggling is that with all this practice, most of us are terrible at it. There seems to be an ongoing conflict between science insisting on how important sleep is versus societal pressure to get things accomplished. It gets to the point where people get shamed into thinking that sleeping is a habit of the lazy. In the past, we may have not had enough information to go on. But nowadays there’s a great wealth of information due to the work of sleep scientists and research. The unanimous, undisputed findings of these works is that one of the main factors in prediction, thus prevention, of chronic disease may very well be our slumber habits. 

As you may suspect, if there’s such a thing as “sleep scientists”, that must mean that sleeping is not simply wasting hours away in bed. What may come as surprise is how complex and intricate of a process it actually is. I’m going to discuss the mechanisms of sleep, the importance of the individual components, and why it’s important to know these things so that you can modify your sleep routine.

Sleep Architecture

Some may already be familiar with the term “sleep cycles”. You may know that there’s different “levels” to sleep. Common sense would suggest that these levels begin with light sleep, build up to deep sleep, and eventually taper back down to light sleep before we wake up. Well, in this case, common sense will fail us. There’s tons of published work describing the different cycles, so I won't try to reinvent the wheel. 

from www.sleep.org :

Stage One: Within minutes (sometimes even within seconds!) of nodding off, your brain produces what are called alpha and theta waves and your eye movements slow down. This introduction to sleep is relatively brief, lasting up to seven minutes. Here, you are in light stage sleep, which means that you're somewhat alert and can be easily woken. It’s during this stage of sleep that people often indulge in brief “catnaps.”

Stage Two: During this stage, which is also fairly light, the brain produces sudden increases in brain wave frequency known as sleep spindles. Then brain waves slow down. If you were to schedule a “power nap” you’d want to wake up after this stage of sleep.

Stages Three & Four: This stage is the beginning of deep sleep, as the brain begins producing slower delta waves. You won't experience any eye movement or muscle activity. At this point, it becomes a little harder for you to be awakened, because your body becomes less responsive to outside stimuli. The brain produces even more delta waves and you move into an even deeper, more restorative stage of sleep next. It's most difficult to wake up during this stage. This is when the body repairs muscles and tissues, stimulates growth and development, boosts immune function, and builds up energy for the next day.

Rapid Eye Movement (REM) Sleep: You generally enter REM sleep about 90 minutes after initially falling asleep, and each REM stage can last up to an hour. An average adult has five to six REM cycles each night. During this final phase of sleep, your brain becomes more active. This is when most dreaming occurs, your eyes jerk quickly in different directions (hence, the name!), heart rate and blood pressure increase, and breathing becomes fast, irregular, and shallow. REM sleep plays an important role in learning and memory function, since this is when your brain consolidates and processes information from the day before so that it can be stored in your long-term memory.

Before we get into the discussion, you need to know that stages 1-4 are referred to as “non rapid eye movement (NREM), while stage 5, as you’ve already learned, is referred to as ''REM”.

You may already be finding this quite interesting, in the sense that no, we don't simply “pass out” and yes, there is a difference in the types of sleep that we experience every night. What I find fascinating is the fact that it’s not a linear progression. It’s actually a repeating cycle. What I mean is that we don't go through the process one time, but rather cycle stages 1-5 multiple times throughout the night. It takes approximately 90 minutes to progress through all stages before we go back and start all over again. This means that we spend several stints in NREM and REM cycles nightly. If we want to get a bit more precise, about 75-80% of sleep is NREM, the remaining 20-25% is REM. What’s even more fascinating is that the cycles are not consistent. The first time through the process, NREM phases are long, compared to very short REM phases. As the night progresses, NREM phases get shorter as REM gets longer. Hence, we do most of our dreaming when we’re closer to waking up. But wait there's more…. As we age, sleep patterns shift to where NREM sleep is shorter and REM sleep is longer. So, babies spend a lot more time in NREM sleep than their grandparents. 

Our Brain: The Body’s Computer

To make better sense of how these processes interconnect, I like to use a computer analogy. It is during NREM sleep that the body is typing up content and actually creating work. But it is during REM sleep when the “save” button is pressed and all that work is stored in the hard drive. Both things need to happen to complete the process. If you do all the work but don't save, you’ll have stored nothing. In contrast, if you do no work, it doesn't matter how many times you press the save button, there’ll be nothing there. This is how our brains manage the sleeping process.

Connecting the Dots

Let's start putting some of this together. You know how people talk about “8 hours of sleep”? It turns out, 8’s not just a random number. Sleep research has revealed that in order for humans to put in a full sleep, complete all processes, and get all the benefits, we need to go through all the sleep cycles an average of 5-6 times. If one cycle takes approximately 90 minutes, it comes out to 7.5 to 9 hours.

Also, you know how you may have heard, possibly from your fitness coach, that you should be in bed by 10:00 pm? Well, it turns out that circadian rhythm dictates sleep cycle distributions, mainly via the hormone melatonin. This means that if you go to bed at 2:00am, your brain will start you at shorter NREM cycles and longer REM cycles, as it does every night, later into sleep hours. Conversely, if you go to bed early, but wake up at 3:00am to do shift work, you’ll be getting a lot of NREM sleep to very little REM sleep. So think back to the computer analogy. In the first example, you’re pressing the save button many times without getting much work done. In the latter, you’re working quite a bit, but not pressing the save button. This is where things start getting a little tricky and why you may have heard me say that it’s not only how many hours of sleep you get, but also which hours you’re sleeping. To drive this point a little further, consider the following timeline as it pertains to physiology during the night.

11.00 PM – 1.00 AM: LIVER ELIMINATES TOXINS AND REJUVENATES ITSELF 

12.00 AM – 4.00 AM: BONE MARROW (MEDULLA OSEA) PRODUCES BLOOD 

1.00 AM – 3.00 AM: GALLBLADDER (VESICULAR) ELIMINATES TOXINS AND REJUVENATES ITSELF 

3.00 AM – 5.00 AM: LUNGS ELIMINATE TOXINS AND REJUVENATE THEMSELVES 

4.00 AM – 7.00 AM: COLON ELIMINATES POISONS AND REJUVENATES ITSELF (THIS IS THE PROPER TIME TO EMPTY YOUR BOWEL)

7.00 AM – 9.00 AM: VITAMINS, MINERALS, PROTEINS AND NUTRIENTS ARE ABSORBED IN YOUR SMALL INTESTINES (OPPORTUNE TIME FOR BREAKFAST)

I must note that this is an Ayurvedic Bio Clock model. While we can say with reasonable certainty that these processes do occur throughout the night on a given timeline, the actual timing of what Ive just described is theoretical. Yet, research suggests that if the body is not in full rest and undergoing sleep cycles during these times, some of these processes may not occur at the extent that is required.

Sleep Aids

Before getting into this, I will say that in my opinion, the best way to fix your sleep is to work on daily rhythm. This means waking up at the same time every day, adequate hydration, consuming nourishing foods, avoiding stimulants, exercising, and limiting blue light exposure after sunset. Yes, there’s supplements that could help improve sleep timing and quality, but I see these as “bio hacks”. They’re ways that enable one to overreach and treat symptoms without actually fixing behaviors that are the root cause. What I'm more interested in addressing is practices that are commonly associated with better sleep but are actually detrimental.

Alcohol - The “night cap” is very commonly referenced as something that helps you sleep. Yes, consumption quantity has quite a bit to do, but overall, alcohol serves as a sort of sedative. It will, indeed, help one fall asleep and get solid NREM sleep. The problem is that as it begins to be metabolized hours later, it will greatly disrupt REM sleep. Think about it. When you’ve gone out boozing at a party, you come home, fall dead asleep, and wake up 10 hours later. You didn't move, you didn't roll over, as far as you're concerned, the world stopped turning while you were asleep. Question is, have you ever fallen asleep drunk and remember a dream the following day? Most likely not and the reason for this is lack of REM sleep.

Drugs - This term gets uncomfortable for some people, but if you’re using Ambien, Lunesta, or Restoril among many others, you’re taking sleeping drugs. All of these induce sleep via the same sedative effect described above for alcohol and alter sleep cycles in the same way. 

Bottom line, getting good sleep is one thing, “passing out” is very different.

Sleep Chronotype

There’s very interesting research coming out on whether or not there’s such a thing as a “night owl”. We’ve all heard of people who describe themselves as a “morning person” and others who insist that they simply do not operate until later in the day. To be honest, I used to think this was total bullshit. But it turns out there may be some truth to it. Morning people are referred to as “larks”. Those who take a little longer to get going, they’re “night owls”. What we know so far is that it may be a pretty even split, but for the most part, there's more female larks than night owls versus an almost even population of the two for males. But, before you get too excited, you should know that this doesn't mean that the two groups have opposite circadian clocks. Larks will experience better energy levels and enjoy greater health if they’re asleep by 9-10pm and wake up at 5-6am. Night owls have a difficult time falling asleep at those times and consequently waking up that early. They fare a lot better with a 11-12 pm bedtime and waking up at 7-8am. Unfortunately, night owls have it a little rough in life as modern society has its own rhythm and if you wake up at 7-8am, you’re going to be late for most jobs and your kids will most likely be expelled from school because of unexcused tardiness. What's important to see is that even though we may be wired a little differently, general rules still apply. An approximate bedtime of 10:00pm is healthy and we should get 7-9 hours of sleep.

By no means is this all the information that you need to know about the benefits of sleep. There will be a continuation to this article where I’ll discuss how sleep deprivation negatively affects us in different ways. These include, but are not limited to, exposure to chronic disease, psychological health, mental acuity, productivity, and weight management. For now, I hope this little bit of information helps in making sense of what’s happening while you sleep and can provide direction on basic habits that you can implement to make sure that you allow your body to undergo the processes required to promote greater health.