I have always had one question about sleep that I never really looked into. Why does sleep feel so short? I decided to finally answer that question with a little research. Why does it feel like I have only been asleep for a few minutes, when hours have passed?
Sleep feels so short due to your brain disabling the areas of itself that controls consciousness. This happens during SWS, or Slow-Wave Sleep, one of the major phases of sleep. Your brain sort of “blacks out” during this phase and you are unable to perceive time properly while in this non-dream state.
What is Slow-Wave Sleep?
Slow-Wave Sleep, or stage 3 sleep, is the third stage of sleep and the last stage before REM sleep, or a non-dreaming state. In this stage of sleep, your brain begins to block outside stimuli in order to enter REM sleep, or a dreaming state. Your brain begins emitting delta waves that slows down your brain to a resting state.
Slow-Wave Sleep is is deepest stage of sleep and is also very difficult to wake up from. Ever wake up and see that you have a missed call on your phone and never heard it ring? You were more than likely in slow-wave sleep. When you are in this stage, it is very difficult to wake up from. If you are awakened during this stage, you will be a little disoriented. The disorientation will pass shortly, but just imagine your computer rebooting. It has to load the hardware, software, time and date. Your brain has to do something similar.
I know there have been times that I have woken up and not know what day it is, or where I am. This is the disorientation from slow-wave sleep. This is also helps to answer “why does sleep feel so short” question.
Why Do We Have Slow-Wave Sleep?
There are 4 stages of sleep that are scientifically accepted. Your body will go through each one one step at a time.
Slow-Wave sleep is the deepest non-dream stage that your body can achieve. This is important since this is the stage that your brain begins to disconnect you from outside influences to begin REM (Rapid Eye Movement) sleep, also known as a dream state.
While you are in this state, the body begins to repair muscles and tissues, conserves energy for the next day and helps improve your immune system. Some very important functions! The delta waves in this stage help keep your body calm when you enter REM sleep.
How does Slow-Wave Sleep Slow the Perception of Time?
Time progresses forward if you stay awake or not. It only seems to change because you are “tuned out” while your brain is in this state of sleep. During this stage of sleep, your brain begins producing slower and slower delta waves. These delta waves are not completely understood by science, but we do know that it only occurs during the slow-wave sleep.
The delta waves that are produced at this time is essentially the lowest form of brain activity that we can do. Any lower, and you would be considered brain dead. It is nothing to be concerned about, since if you are 21 or older, you have entered this state well over 7,000 times! Assuming you sleep once per day, every day, for the past 21 years. I know there are people you have met that may seem like they live in this brain dead state, but they are not.
There are people that believe these delta waves provide access to God, or a Collective Intelligence. I am not going into that here, but feel free to google that and enjoy that rabbit hole.
What Happens During Slow-Wave Sleep?
I have already mentioned why we have it, but what exactly goes on here? Ill tell ya.
During this phase, your brain begins to produce what is known as “Delta Waves.” These delta waves allow your brain and body to disconnect from the outside world and prepare your body for a dream state.
During this stage of sleep, your body boots it’s immune system, begins to repair muscles and other tissues and store’s energy for the next day. It is also believed that since REM (Rapid Eye Movement) is the next stage of sleep, it is important to disconnect your motor functions from brain at this time. During dreaming, you can experience very vivid dreams. If you had a dream you were running in a field, does your legs start running in the real world? No. That is one of the reasons for the delta waves and the stimuli disconnect.
Why Do We Sleep in Stages?
Scientists believe that when you sleep, your brain processes what you have learned and experienced since the last time you slept. Its common knowledge that your brain cells builds new connections when you experience situations during the average day and during sleep, it is widely accepted that your brain uses this time to filter out what is important, and what is not.
As an example, lets think of a food you do not like. Can you remember the last time you tasted it? What did it taste like? Can you remember what was the time of day the last time you tried it? How about the weather that day? Was it sunny in the morning, then thunder stormed that afternoon?
Odds are, you do not remember the details surrounding that memory, but can remember the event itself. This is what scientists believe happens during sleep. Your brain eliminates the “useless” information, remembering only the important events. Can you remember the names of all the kids in your 6th grade English class? I bet you knew them when you were there, but not anymore. They were important at the time, but not anymore. Your brain needs that space for new information.
In order for the brain to process and store this new information, it blocks outside stimuli and disconnects from your motor functions. In the off chance that you enter REM sleep and begin to dream you are boxing with Muhammad Ali, you do not want to start throwing punches in your bed, or wherever you fell asleep, would you? This is why your brain disconnects your body.
What are the Stages of Sleep?
Ther are 4 different stages of sleep before you reach REM sleep, or the stage where you dream. I will cover these quickly, since it is not the main topic of discussion.
- Stage 1: Here, you have just closed your eyes. This is a very light sleep where you are easily woken from. Your eyes will move very slowly and you may have sudden muscle jerks. It is thought that these muscle jerks are your brain checking to see if you are asleep.
- Stage 2: Only small and random brain waves are seen and your heart rates drops, as well as your body temperature.
- Stage 3: Your brain waves slow dramatically and it begins to produce delta waves. You are technically in a deep sleep here where you can experience parasomias like night terrors, sleep talking and bed wetting.
- Stage 4: At this stage, your brain is doing pretty much nothing but emitting delta waves. Your brain is now in its deepest sleep before entering into a dream state.
- Stage 5: Rapid Eye Movement (REM) Sleep. Your brain is extremely active during this phase and gives the same signals as if you were wide awake. Your eyes move rapidly and is assumed it is you interacting with your dream. When you wake up in this state, you will usually remember your dream for a short period.
These are what you go through during a regular sleep cycle. The time spent in each stage can vary from person to person, or animal to animal since these work with all mammals.
So, Why Does Sleep Feel So Short?
TL;DR Version (too long, didn’t read) During the third stage of sleep, your brain disconnects you from your body and reaches a very low state of brain activity. Since your brain is what processes consciousness and time, it essentially blacks out and just seems like you just went to sleep.
I hope this has helped with a better understanding of why it seems like you sleep for 20 minutes and hours has passed by. You are not secretly a time-traveling time lord and your bed is definitely not a TARDIS. (Doctor Who reference for those non-geeks.)