Sleep. We all know it’s good for us. Whether it was your mom, a grandparent, a sibling, or even the internet, someone in your life has told you that you need sleep. I’d even hazard a guess that many people in your life have told you that you need sleep.
But how much do you really know about how sleep actually works? This is my first blog post, so I decided to write a little about something I’ve recently been learning in my “Intro To Psychology” class, and I find it utterly fascinating. We all know that at night we shut our eyes and (hopefully) enter a different state of consciousness that our bodies need, but it’s not just one single state of inactivity where we lie there unconscious for 7 hours or so until waking up. So, what actually happens while we sleep? Let’s get into it.
Humans cycle through 4 different ‘stages’ during sleep, categorized by our brain activity. Researchers have been able to observe these variations in our consciousness by using an electroencephalograph. But that’s a very long word, and we don’t need to know it, so we’re going to refer to it by its widely used acronym: EEG.
Basically, an EEG tracks and records brain wave patterns by detecting electrical activity in our brains. So by using an EEG, we’re able to look at the different rhythms in wave patterns of our brain activity and identify 4 distinct stages while we sleep.
So, our 4 stages are broken up like this:
Stage 1 (5-10% of sleep in adults): This is the transitional stage of light sleep where we are hardly asleep. If you’ve woken while in stage 1 sleep and someone asks if you were asleep, you’ll probably say no, because we don’t even realize that we’re sleeping in this stage. This is generally the part of sleeping when our body starts slowing down and we feel ourselves being lulled. If you’ve ever felt like you were falling or floating right as you fell asleep, you were in stage 1! Sometimes if you wake up during this stage, your body will jolt or feel like it’s falling.
Stage 2 (45-55% of sleep in adults): As we enter stage 2, our body continues to slow down. It’s a lighter sleep, so while slight noise won’t wake us, we are still far easier to wake up than in the next stage. Our heart rate, respiration rate, muscle tension, and body temperature all drop. Fun fact: this is why we generally feel colder/need blankets at night while we sleep even though we don’t walk around all day wrapped up in comforters. Our body temperature actually decreases when we sleep, so we need those blankets to stay toasty!
Stage 3 (15-20% of sleep in adults): As our bodies slow down, our brain waves also become slower in frequency. During stage 3, we enter a deep phase of sleep that’s also referred to as “slow-wave sleep”, because our brain waves in this stage of sleep have low-frequency when looked at with an EEG. This is the stage of sleep where you are deeeeeeply asleep and nothing will wake you!
REM – Stage 4 (20-25% of sleep in adults): REM (stands for Rapid Eye Movement) is the most fascinating and active stage of sleep. As we cycle through the stages of sleep, we enter REM. During REM, our heart rate, blood pressure, and oxygen consumption all increase – this is all very similar to when we are awake. Why is it called the Rapid Eye Movement stage, you might ask? It’s because during this stage, we actually experience muscle paralysis. Our bodies quite literally become paralyzed, and we’re unable to move. However, our eyes are the only part of our bodies that are not paralyzed in this instance. So, if you happen to lift the eyelids of someone who is in REM (please ask for consent before lifting someone’s eyelids while they sleep – that’s creepy), you’ll actually see that their eyes are moving (which is also creepy). Our eyes dart around during REM as if we are awake and actually seeing whatever it is that’s going on in our brains.
This begs the question: why do our bodies freeze up during REM? It’s because during REM our brains are seriously active. REM is when we do most of our dreaming. If our bodies weren’t paralyzed during this stage, we would be physically acting out our dreams/active minds, and that would be very dangerous, and I’m sure you can imagine why! There’s actually a very rare and scary disorder called REM sleep behavior disorder where people are not completely paralyzed during their REM stage of sleep and do act out their dreams. Just imagine that you are killing someone in your dream – it could end VERY badly for the person sleeping next to you if you aren’t paralyzed.
This is why if you’ve ever had a dream where your mind is telling you to run away from something or scream, but you can’t do it no matter how hard you try in your dream, it’s because you… seriously can’t. Your body is paralyzed – you can’t go anywhere or do anything. That’s why REM sleep is so interesting – there’s so much going on between our minds and our bodies in this stage!
Our sleep patterns do change as we get older, though. Babies get about 50% of REM sleep during their first few months of life, and then the percentage of sleep spent in REM starts to decline. The average percentage of REM sleep that we get continues to decrease until adolescence, and then it generally stays stable (taking up about 20-25% of our total sleeping). As we continue to age after adolescence, the total amount of sleep that we actually need does decline (this is why teenagers need more sleep than adults), but our percentage of REM stays roughly the same.
However, while there is a “normal” idea of what a night’s sleep cycle should look like, there are many people whose sleep cycles do not resemble this, and sleep disorders are also common.
Some examples of sleep disorders include:
Insomnia: chronic difficulty falling or staying asleep – the most common sleep disorder.
Narcolepsy: the body’s inability to properly differentiate between sleeping and being awake. Someone who has narcolepsy actually slips far too easily between states of consciousness and unconsciousness, which explains why they will quickly fall asleep during random times throughout the day or constantly wake up when they are sleeping. It’s like constantly being on the edge of sleep or wakefulness.
Sleep Apnea: when your breathing periodically stops and starts as you sleep.
Restless legs syndrome: an irresistible need to unceasingly move your leg, generally while sitting or lying down.
Sleep walking: when a person wanders around while remaining asleep.
Sleep is very complex, and I know we’re all busy people and don’t have the time (or quite honestly, the energy) to read 10,000+ words about sleep in one sitting. So hopefully this was just enough to teach you a little bit about the basics of what our sleep cycle looks like with its 4 stages. In another article, we’ll talk a little bit about the benefits of sleep, what it actually does for us, and some of the theories about the different stages and the role they play.
We can also get into sleep disorders, how to treat them, and how to improve our sleep!
Hopefully tonight you get a proper sleep and spend enough quality time in each necessary stage. 😉