The Four Stages of the Sleep Cycle
With several pillars of health to consider when seeking to optimize your overall wellness, many often forget about sleep and its importance. As a result, many fail to reach the deep stages of sleep and instead wake up unproductive, unenergized, and frankly unhappy a lot of the time.
Whether or not this is a result of the persistent hustle culture or sleep when you're dead analogy that is constantly being pushed in today's society, it's undeniable the vital importance of quality sleep.
Additionally, it's often debated how many hours of sleep we require on a nightly basis in order to achieve an optimal level of rest. While it's typically agreed upon that 7-9 hours is ideal, sleep duration is not the only component of sleep quality to consider; it's also important to consider and understand the entirety of the sleep cycle and the role it plays in sleep quality.
With that said, in what follows, we'll be defining the four stages of the sleep cycle, their roles, and how you can optimize your sleep schedule so as to wake up feeling refreshed and recharged every time.
The Four Stages of Sleep
Generally speaking, there are four stages of sleep that one enters throughout a period of rest. These four stages are as follows: awake, light sleep, deep sleep, and the ever-popularized REM sleep.
Notably, the first three stages are categorized as NREM, or non-REM sleep, with the fourth stage, of course, being REM sleep…
While each is important in their own respect, they all play individual roles in maintaining and achieving optimal sleep quality, thus improving and optimizing one's mental and physical health in the process.
Additionally, as you progress through each stage of the sleep cycle, it becomes increasingly more difficult to be awoken, hence the deeper the sleep. With that said, the following will be a detail into what each stage of sleep is and what role it plays in the sleep cycle.
Stage 1: Awake
Obviously stated, stage one of the sleep cycle is the phase in which you first place your head on the pillow with the aim of falling asleep. Evidently, the time it takes for you to reach stage two will largely depend on how tired you are and how isolated your environment is from distraction.
Because your body and brain have yet to fully relax, brain activity is still apparent in this stage. As such, you may experience brief moments of “dozing” with brief moments of awakening.
In short, this stage can be characterized by the time spent in bed to the moment at which you officially fall asleep. Stage 1 typically lasts 1-5 minutes.
Stage 2: Light Sleep
Once you've dozed off into a state of subdued unconsciousness and your muscles have fully relaxed, your body will begin to slow its breathing, reduce its heart rate, and reduce its internal body temperature. This is what characterizes stage two of the sleep cycle.
While many consider this to be sleep, your brain still shows small amounts of activity, thus defined as light sleep. While this stage typically lasts anywhere between 10-30 minutes during the first sleep cycle, it depends largely, however, on how isolated your environment is from distraction; many can still be awoken quite easily in stage two…
Stage 3: Deep Sleep
Otherwise known as deep sleep, stage three is arguably the most important stage for restoration and recovery. Without reaching deep sleep, you're likely to awake groggy and grumpy.
Characterized by a further reduction in breathing rate, heart rate, pulse, and brain activity, stage three is known to be a difficult stage to awake someone from their slumber. Further, it's also the stage that promotes blood flow, muscular recovery, hormonal release, and cellular repair.
Notably, stage three is the longest of the first three stages, especially during the first half of the night. Upon exiting this stage, you'll have officially entered what's known as REM sleep…
Stage 4: REM Sleep
REM sleep is the stage at which we experience rapid eye movement and it becomes increasingly longer as the night goes on. In other words, while the first phase of REM may only last a few minutes, the final phase may last upwards of an entire hour.
Unlike the first three stages which happen to experience a reduction in brain activity, breathing, and heart rate, stage four happens to result in the opposite. As such, this stage is scientifically presumed to be imperative for cognitive functions such as memory, deep learning, and creativity.
As you can imagine, REM sleep is likely where you'll experience the most vivid of dreams… Because of this, REM sleep is also characterized by a level of paralysis, intended to inhibit body movement so as to not physically act out the dreams you're experiencing.
Optimizing Your Sleep
There are several ways to improve your overall sleep quality, whether it be lifestyle interventions or otherwise…
Firstly and arguably most importantly, it's imperative that you follow a consistent sleep schedule. Failing to do so will only result in a disruption to your internal clock, thus an impairment to your overall sleep quality.
Unfortunately, this can't always be avoided, as life can become quite busy… In such a case, it's your personal responsibility to do all that you can to optimize your sleep environment so as to increase the likelihood of a quality night's sleep.
Some of the best practices and lifestyle interventions to aid in such an endeavour include but are certainly not limited to the avoidance of blue light before bed, the reduction of caffeine consumption, the frequency of exercise, the optimization of your bedroom temperature, and if need be, the use of melatonin supplementation.
If sleep persists to be of concern and the lifestyle interventions discussed above are largely ineffective, it might be best to consult with a sleep expert or medical doctor to further examine your biology and physiology.
The good news is that there is an abundance of solutions no matter where you land on the spectrum of sleep quality! It's up to you, however, to seek out said solutions.
-  Stutz, Jan, Remo Eiholzer, and Christina M. Spengler. Effects of evening exercise on sleep in healthy participants: A systematic review and meta-analysis. Sports Medicine 49, no. 2 (2019): 269-287.
-  Patel, A. K., Reddy, V., & Araujo, J. F. (2020, April). Physiology, Sleep Stages. StatPearls Publishing.