Sleep Cycles: The Five Stages Explained

Sleep Cycles

Falling asleep might be a simple activity, but properly resting your body and waking up revitalized is more difficult to achieve when you do not understand how sleep cycles work. According to data generated from a subset of the more than 3 million people covered by MediKeeper, only 48% of respondents sleep soundly and feel rested most of the time. This is in comparison to the small 2% who feel rested all of the time. Considering how active of a role sleep plays in repairing our bodies, these are not promising results. One of the largest misconceptions about sleep is that quality is determined by how many hours you obtain. While this is true, as continually depriving yourself of sleep can put you in a sleep debt that is hard to get out of, a ‘good night’s sleep’ is more about quality than it is quantity. Waking up feeling refreshed and ready to take on the day involves not only getting the proper amount of rest, but the correct duration of sleep.

What Are Sleep Cycles?

Timing is everything, especially with sleep cycles. During a 90-minute period, we move through five stages of sleep that make up one sleep cycle. The first four stages consist of non-rapid eye movement (NREM) sleep, and the fifth stage is called rapid eye movement (REM) sleep. Each of these stages are important for replenishing different parts of your body, and a good night’s sleep should contain four or five complete cycles.

Stage 1

Stage one of sleep, the transitional phase, is both short and restless. It feels as if one is floating in and out of consciousness, because muscle activity is only beginning to slow. During this stage, there is a sense of awareness that might feel like you are partially awake. You can still hear your surroundings and, if woken prematurely, can recall some visual images. This period of half-conscious drowsiness eventually leads to a light sleep. Hypnic myoclonia, or muscle contractions, followed by a falling sensation that jolts you back into consciousness is also common during this stage.

Stage 2

Almost 50% of time spent asleep is spent in stage two. It is a continual progression of stage one in which the heart rate begins to slow and the core body temperature decreases. Similar to stage one, muscle contractions are common, but these are more unstructured in their alternations between muscle tone and muscle relaxation. Although stages one and two are both lighter sleep stages, they serve an important body reparating function. Stage two, specifically, is where your body processes memories and emotions and regulates its metabolism, making it crucial for body maintenance.

Stages 3 & 4

Stages three and four are often combined because they are periods of slow wave sleep (SWS). It is an NREM phase of sleep where brain waves slow to delta waves, and your body enters the deepest phase of sleep. If you try to wake someone up during stages of deep sleep, then they will most likely be disoriented and groggy for minutes after they awaken. Dreaming during these stages are no longer occurring, because the thinking parts of your brain are turned off. The focus is placed on rebuilding and repairing the body. Hormones are released to aid in bone growth, appetite control, and replenish tissues that were exerted over the course of the day. These hormones are essential to the development of a strong body and consumption control, which is why it is time to start making your health a priority.

Stage 5

Stage five is the only stage of rapid eye movement (REM) in which the brain bursts with activity. It is when most dreaming happens, and its name is derived from the action of your eyes moving rapidly in different directions. Time spent in this stage decreases as you get older. Children spend almost 50% of sleep in REM, while adults only spend 20%, which explains the decrease in dreams as you get older. Dreaming is a result of the heightened, desynchronized brain waves that are sharpening your daytime functions.

Although the brain is very active, your body is paralyzed by inactivity. Heart rate increases and your breathing becomes shallower and more irregular. REM’s main function is improving the brain; it is very important for emotion regulation and memory. This is why the body is so paralyzed.

At the end of stage five, the body begins to awaken. This process involves body temperature rising in order to prepare it for the daily activities ahead.

Improving Your Sleep Quality

Understanding how sleep cycles work are important to obtaining that seemingly impossible good night’s sleep that we all strive for. It is important to prioritize sleep the next time you consider staying up late for a work project or extra TV episode so that your body can properly heal from the day before. Depriving your body of its reparation process will weaken your immune system and cause both short and long term illnesses that will take a larger toll on your productivity. While there is no such thing as too much deep sleep, too little, on the other hand, is what makes us wake up feeling tired. Sleeping for the recommended eight hours a night therefore ensures more time in the deep sleep stages. Technology companies are well aware of sleep cycles and their impact on our sleep quality and productivity. Many fitness trackers, wellness portals, and websites have components that measure your sleep quality and provide recommendations for improvement. With all of this information, perfecting your sleep schedule is no longer impossible.