Sleep Cycle

sleep cycle

A Sleep Specialist's Easy Guide To Understanding Sleep Cycles

Sleep Cycle – Most species are classified as either nocturnal or diurnal. Simply put, nocturnality means being active during the night and asleep during the day. Nocturnal animals have physical characteristics that help them thrive and survive in the dark. This includes a heightened sense of smell and large eyes that can see clearly in low-light conditions. The opposite of this is diurnal — or being awake and active during day time, and asleep and inactive at nights.

Human beings, by nature, are diurnal creatures. The National Sleep Foundation says that the average adult needs around seven to nine hours of sleep every night. But more than the total number of hours spent sleeping, the quality of sleep is so much more important. During sleep, the body is supposed to complete multiple cycles of all the stages of sleep.

Article at a Glance

The Importance of Regular Sleep Patterns

Human beings have built-in biological clocks that regulate our sleep and wake cycles and determine our sleep patterns — or the body’s circadian rhythm. The circadian rhythm is also influenced by environmental factors like sun and light exposure. It also regulates the release of hormones, hunger and digestion, and other bodily functions. When the circadian rhythm is disrupted, it could have negative effects on our health. Chronic sleep disruptions put you at risk for many health issues like depression, anxiety, obesity, diabetes, high blood pressure, and heart disease to name a few.

Your Sleep Cycle: What Goes On In Your Brain?

The circadian rhythm signals the body to produce melatonin. It is the hormone that is responsible for making us feel drowsy and primed for sleep. Once we do fall asleep, the body does not shut down, nor does the brain. This is unlike what was originally believed before scientific research revealed otherwise. Far from it, in fact. Instead, we enter a sleep cycle — it’s a whole new world for our brains.

It only looks like your brain and body are entering a passive stage when you fall asleep, but your brain actually shows incredible activity that can be classified into two parts, the Rapid Eye Movement sleep or REM sleep and the Non-REM sleep or NREM. On an average night of sleep, one can go through five or six cycles of NREM and REM phases of sleep.

Your sleep cycle is not the same as your circadian rhythm. While the circadian rhythm controls the overall sleeping and waking functions of the body, a sleep cycle is something your body enters into while asleep. On average, a single sleep cycle takes around 90 minutes. The average person will undergo multiple sleep cycles a night.

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The Different Stages of the Sleep Cycle:

Stage N1

This stage begins with feelings of drowsiness and progresses into a very light and very shallow sleep. This stage will last for about five, but up to 10 minutes in duration. The brain activity decreases. At this stage, a person will experience sleep starts or hypnic jerks; these are involuntary jerky movements that can mimic the sensation of falling, which usually ends up waking the sleeper.

Stage N2

The second stage of NREM lasts a little bit longer, up to nearly half an hour. This stage is still considered a light form of sleep, and a person in NREM can easily be roused. The body also undergoes some physical changes during this phase. The heart rate slows down, along with the breathing. The muscles start to relax, and brain waves also slow down. About half of the total number of hours a person spends asleep will be in the N2 Stage of sleep.

Stage N3 and N4

The third and fourth stage of the NREM sleep is also called slow wave, deep sleep, or delta, named after the slow brain wave that characterizes this stage. This sleep stage may last for less than an hour, but it is regenerative, and essential to waking up feeling refreshed and energized.

It is more difficult to rouse a person when they are in this stage of sleep. And when they do wake up, they wake up disoriented. (A tip for those who want to take a quick power nap, keep it under 30 minutes, so you don’t wake up feeling groggy.)

At this stage of sleep, some sleep talking and sleepwalking can occur, as well as vivid dreaming. On average, 15 percent of one’s total sleep time is spent in this stage.

REM Sleep

REM (rapid eye movement) sleep starts about 90 minutes after you fall asleep and each REM stage can last for up to an hour. This phase is marked by the swift left to right, up and down movements of the eyes behind your closed eyelids; hence the name. There is no definitive scientific explanation for this, but one theory is that it is linked to dreaming and brain wave activity because this deep sleep stage is also characterized by increased brain activity. This is the stage where a sleeping person may have dreams or night terrors. Physically, your body will undergo some changes as well. Your breathing will become fast and irregular; your heart rate and your blood pressure will spike up as well. Meanwhile, your body temperature drops and your muscles relax to the point of immobilization.

A Word About Sleep Disorders

A Word About Sleep Disorders

There are many different factors that can cause sleep to be elusive. Some are lifestyle based and temporary, while others may have rather serious underlying health issues that could be the root cause.


An example of short-term sleep disorder is jet lag. It’s the disruption of our biological clock that happens when we cross time zones. This is a condition that can resolve itself in a few days even without intervention; however, if you are a frequent traveler, you may want to consult your doctor.


On the other hand, some examples of the more serious sleep disorders include insomnia caused by depression and anxiety, sleep apnea, and narcolepsy. If you are suffering from insomnia, or if you find yourself waking up in the middle of the night to go to the bathroom, your sleep deprivation or sleep interruptions might have a physiological cause and will need treatment. It is important to schedule a visit with your primary doctor or sleep specialist regarding your sleep pattern.

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Simple Tips to Promote Restorative Sleep

Unfortunately, sleep does not come easily to everybody. For a wide variety of reasons, many people end up tossing and turning each night, unable to get a good night’s rest. We all must do what we can to help our body recalibrate and get back to a proper sleep schedule. This could include a number of lifestyle practices, changes, and additions such as limiting screen time, investing in a good mattress and pillows, installing blackout drapes, using a sleep cycle calculator, or maybe even seeing a trained specialist that can prescribe appropriate medication or therapies.

Don’t smoke

Not only is tobacco and nicotine (in any form) very problematic for your health and the environment, but research also shows that smokers have a low rate of REM sleep. Meaning, they’re not getting the maximum restorative benefits of sleep in the N3 stage.

Avoid alcohol, especially when you are about to sleep

You might think that alcohol will knock you right out and give you a good night’s sleep, but in reality, you might fall asleep, but an alcohol-induced slumber will keep you in the lighter stages of sleep, and you will not wake up well-rested.

Eliminate caffeine

Another example is consuming too much caffeine, especially too close to your bedtime. The effects of caffeine on sleep patterns include the inability to fall asleep and alertness even in the wee hours of the night. That last part might not sound too bad, especially if you are trying to catch up on work, but habitual sleep deprivation can have harmful effects on your overall health.

Follow a set routine

A set bedtime and waking up time is good for the body because it craves routine. Try your best to stick to a schedule of sleeping at nights and being awake during the day time.

Check your medication

Some drugs, especially prescription antidepressants, tend to interfere with your body’s natural sleeping patterns. It can either keep you from falling asleep or make you feel unnaturally sleepy most of the time. If you find it disruptive, speak to your doctor about alternative options.


To sum it all up, the sleep cycle is a rich and important subject of scientific research. It is an essential part of maintaining optimal health and optimal brain function. Sleep is not just for the lazy who love a good foam mattress, and absolutely nobody should feel guilty for prioritizing sleep. Having healthy sleeping habits are an integral and inextricable part of having a healthy lifestyle, and should not be taken for granted. Also, remember that eating healthy food and exercising regularly can also help get your sleep patterns on track.

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