Understanding the Sleep Cycle


March 14, 2023 4 MIN READ

sleep cycle

Understanding the Sleep Cycle

It takes an average of 100 minutes for the body to complete a full sleep cycle, your body usually goes through 4 to 6 cycles a night. Each cycle includes 4 stages, though the amount of time your body spends in each stage varies as the night goes on. These 4 stages are split into two main types of sleep – Non-REM Sleep and REM Sleep. It is vital that you understand each of these types of sleep to know how important they are for your body’s health.

Non-REM Sleep

The first 3 stages of the sleep cycle are considered non-REM sleep, or just NREM. It is during NREM that your body builds muscle and bone, repairs tissue, and nourishes your immune system. Most adults spend 75% of their total sleep in NREM sleep.

Stage 1

This first stage of sleep occurs when you are initially falling asleep. Usually only lasting between 5 and 10 minutes, your body hasn’t had enough time to fully relax during this stage. However, your brain and bodily functions are starting to slow, preparing for deeper sleep as the cycle continues.

Since a person hasn’t achieved deep sleep yet, getting someone to wake up during stage 1 of sleep is easy. Sometimes, a person startles awake during this stage of sleep despite not being disturbed externally. This is usually caused by at least one of your muscles suddenly contracting, usually giving someone the sensation of falling. This is known as a hypnic jerk or hypnic myoclonic and isn’t anything to be concerned about, according to medical professionals.

Though nothing of particular importance happens during this stage regarding your body’s need for rest and restoration during the sleep cycle, it is still important as it prepares the body to go into a deeper sleep. If stage 1 continues to be interrupted, the entire sleep cycle can be thrown off.

Stage 2

As your body enters stage 2, it enters a deeper stage of sleep – though not yet what’s considered deep sleep. During this stage, your muscles relax, your temperature lowers, and your breathing and heart rate slow. Brain activity slows during this stage as well, though your brain may still experience short bursts of rapid activity known as sleep spindles. Though medical professionals and scientists don’t understand why sleep spindles occur, or why they vary from person to person, they believe that these bursts of activity have to do with the flexibility of the brain, especially regarding memory and learning.

Usually lasting no more than 25 minutes, this second stage of sleep is what prepares your body for stage 3, also known as deep sleep.

Stage 3

There are many names for stage 3 of the sleep cycle – deep sleep, delta sleep, or slow-wave sleep. These names stem from the way the body acts in stage 3. Some use deep sleep because of how deeply a person sleeps, as it becomes very hard to wake a person as their body relaxes and activity decreases. Others use delta sleep or slow-wave sleep because of the brain activity patterns that occur during this stage. The presence of delta waves is seen to increase sleep quality.

Regardless of the name being used, stage 3 of the sleep cycle is critical for your body’s restoration. It is during this stage that the body can receive the necessary rest it needs to grow, recover, and strengthen. One of the most important functions that are aided during this time is the immune system. This is why many people who struggle with getting a good night’s sleep often find themselves struggling to battle illness and disease.

It is in the earlier cycles of the night that the body experiences deep sleep the most often, usually around 30 minutes. It is during this stage of sleep that, when woken from it, a person will experience disorientation and struggle with reaching full alertness.

REM Sleep (Stage 4)

After the body has cycled through the first 3 stages of sleep, also known as Non-REM sleep, it’s time for the final stage of the cycle. This fourth stage is known as REM Sleep due to the increased brain activity and rapid eye movement that are key characteristics of this stage.

The body usually enters REM sleep around 90 minutes after first falling asleep. Though the brain’s activity is almost the same as when the body is awake, providing the sleeper with intense dreams, some muscles in the body become temporarily paralyzed in the fourth stage of sleep. Unlike the relaxation experienced in deep sleep, REM sleep shows not just heightened activity in the brain but also increased rates of the heart, blood pressure, and breathing.

It is during the later cycles of the night when the body spends the most time in REM sleep. During the first cycle of the night, REM sleep may only last a handful of minutes, whereas later on, it can last up to an hour. Most adults only spend a total of 25% of their total night’s sleep in REM.

Struggling with Your Sleep Cycle, Struggling with Your Health

After understanding the sleep cycle and all of the important functions it provides for the body, it makes perfect sense why individuals who struggle with sleep also struggle to maintain good health.

Whether it’s a sleep disorder like insomnia or sleep apnea negatively affecting your sleep or poor sleep hygiene decisions like not having a good sleep routine or drinking caffeine before bed, if your sleep cycle is being disrupted, so is your health.

As each stage of sleep plays a vital role in the overhaul restoration of your body, it’s key that you’re able to maintain full cycles and get plenty of rest at night. If this isn’t your reality, it’s important that you seek help before your health suffers. Reach out here to the Sleep Science Academy for a consultation. As a leader in helping people overcome sleep struggles, their expertise can provide you with the boost you need to start a healthier sleep journey today!