How sleep works and my experience with it

11/20/2022

An introduction to sleep

Sleep is an underrated part of every healthy lifestyle. There’s a lot of buzz about diet and exercise when discussing health, but sleep is sometimes forgotten because it’s boring and hard to monetize. For me, sleep is the obvious third pillar of a healthy lifestyle and is of at least equal importance as diet and exercise. In this post, I will outline how sleep works, what can be done to improve it, and my experience with sleep.

How sleep works

Sleep is defined as a period of alternating rest and wakefulness, and it’s controlled by internal body clocks with cycles of approximately 24 hours. These clocks are called circadian clocks and their cycles are regulated by many factors including light, darkness, and sleep schedules. These cycles are often called circadian rhythms. The central circadian clock is located in the brain, more exactly in the hypothalamus, and is called the suprachiasmatic nucleus, or SCN for short. I talk a little bit about the SCN in my post on time-restricted eating as well; a concept that is very much related to circadian rhythm and sleep.

Circadian rhythms

A circadian rhythm refers to physical, mental, and behavioral changes that follow a 24-hour cycle. One of these circadian rhythms is our sleep schedule. The circadian rhythms are synchronized with your environment and how you treat your body. Light, darkness, food, exercise, and other factors help cue the circadian rhythm and control when you should feel sleepy and when you should feel awake. This rhythm can be disrupted by so-called fake wakefulness cues such as artificial blue light, caffeine, and alcohol. Everybody’s circadian rhythm is unique. Some people fall asleep late and some people wake up early. I talk more about this in the section on sleep chronotypes at the end of this post. The circadian rhythm also changes as we get older due to our clocks’ signals getting weaker. This means that as we get older we have a harder time staying asleep and we usually wake up earlier.

Sleep molecules

An important molecule when it comes to sleep is adenosine. Adenosine is a neurotransmitter that is released continuously by the body during the day and a rising level of this compound signals to the body that it’s time for sleep. Another important compound for sleep is melatonin. Melatonin is a hormone that is released by the body to make us sleepy. More on melatonin later in the section on blue light and sleep.

The four stages of sleep

So far we have discussed how our sleep schedule works. But what actually happens when we sleep? There are four different stages of sleep.

Stage 1: Awake. This stage includes the time spent awake in bed before falling asleep and also the brief awakenings that occur during the night.
Stage 2: Light sleep. In this stage, muscles relax, the heart rate decreases, and the body temperature drops. You are easily awakened during this stage.
Stage 3: Deep sleep. The main area of focus during deep sleep is to restore and heal the body. In this stage, the blood pressure drops, growth hormone is released, cells are repaired, and waste is flushed from the brain. Waking up at this stage is not optimal. You will feel groggy and disoriented if you awaken in this stage.
Stage 4: REM (Rapid eye movement) sleep. While deep sleep is healing the body, the main area of focus of REM sleep is to energize your mind. In this stage, respiration and heart rate increase again. You may also dream vividly in this stage, which is why the body is immobilized during REM sleep to keep you from acting out your dreams. REM sleep offers great benefits for memory, learning, and problem-solving.

You typically cycle through these stages multiple times during the night. A sleep cycle lasts for about 90 to 110 minutes, which means that if you sleep 7-8 hours you should be cycling through these stages 4-5 times per night. The time spent in each stage varies from night to night and also during the night. In the early portion of the night, more time is generally spent in deep sleep, while REM sleep occurs more at the later stages of the night. If you read between the lines, this means that the body prioritizes physical healing before mental healing when it’s short on sleep. The stages are generally cycled through sequentially and it’s not unusual to wake up once per cycle. Oftentimes you won’t remember these awakenings as their durations are often very short, but sometimes you will be aware of your awakening as it will last longer.

Blue light and sleep

When your eyes are hit by blue light, both natural blue light from the sun and artificial blue light from digital screens, your inner clocks will signal that it’s time to be awake and alert. Exposure to blue light signals the body to release the sleep hormone melatonin roughly twelve hours later. So exposure to blue light, preferably natural blue light in the morning is very beneficial to our circadian rhythm and sleep schedule. Blue light from the sun is most prevalent in the morning and mid-day, while the afternoon and evening sun has more amount of red light. Red light has the opposite effect of blue light. It will tell your body to relax and wind down. So before we had artificial light, our inner clocks would be aligned with the sun. Since the advent of artificial blue light through digital screens etc, our circadian rhythm has taken a hit. Blue light in the evening will suppress melatonin and increase awakeness, which is suboptimal for sleep.

Alcohol and sleep

Alcohol is often seen as a sleep aid due to its sedative effects. While it’s true that alcohol might help you fall asleep initially, it comes with a price in the form of sleep quality. Having alcohol in your system will mean that you spend less time in the REM stage of sleep, meaning that your cognitive capacity will be impaired the next day and you will most likely wake up feeling less refreshed than usual. Even just a couple of drinks will have this negative effect. Alcohol might also have you waking up to go to the bathroom in the middle of the night due to its diuretic effects. Increased snoring is also a potential side effect of alcohol due to increased relaxation, which can stop air from flowing smoothly through the airways. Risk for sleep apnea, a potentially serious condition in which breathing repeatedly stops and starts during the night, is also connected to increased alcohol intake. I will dedicate an entire post to sleep apnea in the future.

Caffeine and sleep

Caffeine can induce a negative effect on sleep for many people due to it blocking the aforementioned adenosine receptors and causing increased alertness and wakefulness. I write more about this in my post about caffeine.

Sleep chronotypes

Since we as humans love to put people in different categories, attempts have of course been made at categorizing people based on their sleep schedule. One such categorization is called sleep chronotypes. According to this categorization, there are four different categories of people:

Lion: The equivalent of an early bird. Wakes up early and is most productive in the morning. Gets tired early in the evening and might have trouble with late social events.
Bear: Tends to be quite aligned with the sun. Works well with normal office hours and has no problem with social events in the evening. Over half of the population is thought to be of this chronotype, which explains why the norms are set to fit this specific chronotype best.
Wolf: The equivalent of a night owl. Wakes up and goes to sleep late and is more productive late at night.
Dolphin: This type generally has a harder time falling and staying asleep. Dolphins are easily awakened and sleep less than the average population. Insomniacs fit this chronotype.

If you’d like to find out which chronotype you belong to, you can take this test.

My experience with sleep

I have for the past 10-15 years or so had a hard time falling asleep and staying asleep throughout the night. Going to bed always induces a small hint of anxiety in me, due to me stressing over if I’ll be able to fall asleep today. When I drink a lot of alcohol, my sleep is always horrendous. I sleep a maximum of 4-5 hours and wake up with a heart that pounds faster and harder than usual. It’s a really bad experience for me, which is a large part of why I don’t drink large amounts often.

Since I learned about the chronotypes, my understanding of my own sleep habits has increased. I’m an obvious dolphin since I’m ridiculously easily awakened and I tend to sleep 6-7 hours rather than 8-9 hours. It’s as if I sleep with one eye and one ear open the whole night. I have throughout the years tried to improve my sleep through different remedies, where some have worked better than others. The list below consists of a compilation of my own tips for improving sleep and what the research says.

Tips for improving sleep:

Blue light-blocking glasses. From time to time I use blue light-blocking glasses at night to try and counteract the effect of blue light on sleep. I use these glasses and I’m quite happy with them. I usually feel more relaxed at night after using them. On that same note, the f.lux software is a great resource for adjusting the light on your digital screen in accordance with the sun.
Dimming lights in the evening. At night I try not to have any bright ceiling lights turned on. Instead, I focus on candle lights and smaller table lights. This is also to avoid suppressing melatonin production.
Getting natural light in the morning. To try and optimize my melatonin production, I often go out and get some natural light in the morning with a 20-minute walk. Living in Sweden, getting light in the morning is a hard thing to do during the winter and fall seasons. I usually try to take my walk later in the morning during these seasons.
Food schedule. I try not to eat too large of a meal too close to bedtime. I usually eat my last meal around 2-3 hours before going to bed, so that my body can focus on healing and reenergizing itself rather than digesting food during sleep.
Exercise timing. I try to avoid doing any heavy resistance workouts at night. I might do some light cardio or just a nighttime walk instead to try and destress. I do almost all of my resistance training before lunch.
No caffeine after 12 PM. Since I’m quite a slow caffeine metabolizer, I don’t drink any coffee after 12 PM.
Cool bedroom temperature. Last but definitely not least is having a cool temperature in the bedroom. Around 18 degrees Celsius is said to be an optimal temperature for sleep, and I really notice the difference when it’s getting too hot in the bedroom.