What Are The Stages Of Sleep And What Affects Them?

By Nadia Khan

Updated February 16, 2020

Reviewer Chante’ Gamby, LCSW


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Everyone, even someone suffering from the most severe insomnia, sleeps eventually. Different people have different sleep patterns, but scientists have identified specific stages of sleep that are natural and beneficial. These sleep stages generally happen in an orderly way unless something happens to disrupt them. Knowing more about the sleep stages you go through each night can help you sleep better and function better in your waking hours.

What Is a Sleep Stage?

A sleep stage is a distinct part of the overall sleep experience. The duration of the sleep stages varies depending on several different factors, which we'll discuss later in this article. One stage of sleep follows another until a complete cycle of sleep is over and another one begins. If all goes well, we wake up from this time of mental activity, after several stages of sleep cycles, refreshed and ready to start the day.


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How Many Stages of Sleep Are There?

You may hear doctors or sleep experts talk about the 4 stages of sleep or the 5 stages of sleep. You may even hear both statements from the same person at different times. It can be extremely confusing to someone just learning about the stages of sleep. You may find yourself asking in frustration, 'How many stages of sleep are there, then?'

The truth is that there are indeed 5 stages of sleep: stage 1, stage 2, stage 3, stage 4, and REM sleep. However, many experts refer to the numbered sleep stages as the 4 stages of sleep and mention REM separately from them, as in 'The four sleep stages and REM sleep.'


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Specifically, What Are the Stages of Sleep?

Scientists have studied the five stages of sleep extensively. Generally, they agree on a basic description for each stage. Sleep progresses naturally from stage one through stage four and REM sleep. When one cycle of sleep ends, another one follows unless you awaken. In a typical night, you spend 50% of the night in stage 2 sleep, 20% in REM sleep, and the rest of your sleep time in the other stages.

Stage 1

Stage one sleep naturally happens first. It is a stage of light sleep. Moments of awareness are interspersed between moments of light sleep. You may also see brief or incomplete images during this stage. You awaken easily. Your eyes may move, but only slowly. Your muscle activity diminishes, although you may jerk awake easily if you're disturbed by a loud noise or other environmental stimuli.

Stage 2

In stage two sleep, you fall a little deeper into slumber. Your eyes stop moving. Your brain waves become slower except for occasional rapid brain waves called sleep spindles.

Stage 3

Stage three sleep is the beginning of deep sleep. Delta waves, which are very slow brain waves, begin to come, although small, fast brain waves are also occasionally present.

Stage 4

In stage four sleep, the faster waves disappear nearly completely. The predominant or possibly the only brain waves present are those extremely slow delta waves. Your eyes don't move, your muscles don't move, and it is very difficult to wake up for any reason. If you do wake up directly from stage 3 or stage 4 sleep, you tend to feel sluggish and disoriented for a few minutes before you fully wake up.

Stages 3 and 4, the deep sleep stages, are when children most commonly wet their beds, have night terrors, or sleepwalk. Although it is rarer, adults may have the same problems during deep sleep.

REM Sleep

Rapid Eye Movement sleep, or REM sleep, is the phase of sleep in which most dreams and nightmares happen. This sleep stage gets its name from the fast, jerky movements of our eyes during this phase. Your breathing speeds up and becomes shallower and more irregular. Your heart rate and blood pressure increase to levels similar to those of wakefulness. You can't normally move your arms and legs during this phase, which keeps you from acting out the dreams.


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How Do the Sleep Stage Cycle Stages Progress?

We typically complete the first sleep cycle with a REM phase that starts about 70 to 90 minutes after we go to sleep. The average complete sleep cycle lasts a total of about 90 to 110 minutes. You spend little time in REM sleep during that first cycle, and more time in deep stage 3 and stage 4 sleep. In later cycles, you have more and more REM sleep, until the last of the sleep cycle stages, which consist mostly of stages 1, 2, and REM.

What Can Disrupt Your Sleep Stages Cycle?

A variety of environmental stimuli can bring you out of sleep at any stage. You may hear a very loud noise such as a car backfiring, a gunshot, or something more common, such as loud music. You may see a brilliant flash, such as that from a sudden fire or explosion, even though your eyes are closed. Even smells can awaken you if they're strong enough. Any of these things can wake you up, especially during the light sleep of stage one and stage two sleep.

You may also bring on the disruptions by taking street drugs or drinking alcohol. People who use nicotine typically sleep only until their bodies begin to crave the drug, often within just 3 or 4 hours. Medications for a variety of medical and mental disorders may disrupt sleep stages as well. (If they do, be sure to mention it to your doctor.)

What Happens When Each of the Stages of Sleep Are Disrupted?

Whether you experience serious effects on your health certainly depends on how much sleep you're losing, but it may also depend on what sleep stage is being disrupted.


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Stage 1 and Stage 2

Because you are frequently moving in and out of sleep, you are accustomed to being awakened during this period anyway. Unless something traumatic happened to wake you or an urgent problem has arisen, you probably won't have any trouble falling back to sleep. The main problem with being awakened during stage 1 or stage 2 sleep is that you can't pass into deeper sleep if these stages are continually disrupted.

Stages 3 and 4

Most of the time we spend in the deep sleep of stages 3 and 4 happens long before we wake. It is in these stages that the body repairs and renews itself, so disruptions can have serious effects on your health.

When you are first awakened, you'll feel groggy and may have trouble remembering where you are. As the disorientation fades, you realize that you have been sleeping. If you have to get up and go somewhere for work or to do errands, you may have to wait to wake up more fully before you can drive safely or accomplish anything at work.

REM Sleep

Being awakened during REM sleep can also have serious effects. Notably, when people are awakened suddenly from REM sleep their self-image suffers. If it happens often enough, it can lead to mood problems. On a positive note, though, people often score much better on creativity tests after they're awakened from REM sleep.

Ways to Track Your Sleep Stages

Concerns about your sleep can be distressing, especially if you are having daytime symptoms that may be caused by problems with your sleep stages. One step you might take is to track your sleep stages to find out how much your spending in each and what the overall quality of your sleep was during the night. There are a few different ways to do this.

Fitbit Sleep Stages Tracking

Many apps and electronic devices have been or are being developed to track sleep. Fitbit sleep stages tracking is available now. The Fitbit Charge 2 sleep stages function allows you to monitor your sleep cycles. All you have to do is wear the Fitbit device when you go to bed, and it does the rest. When you awake, you can see how long you slept as well as how long you spend in light, deep, and REM sleep.


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Tracking Sleep Stages in a Sleep Lab

If sleep deprivation or disruption becomes a serious physical or mental health problem, your doctor may send you to a sleep lab to have technicians there do a sleep study for you. There, you are connected to monitoring devices by leads that attach to your head and body and to the monitoring equipment. With this advanced equipment, the technicians can see readouts that show details of your sleep stages. They then report to your doctor, who can take appropriate measure to improve your sleep.

Using a Stages of Sleep Chart

You, sleep lab technicians, or your doctor can make a sleep stages chart from the information you gleaned from a sleep study or a Fitbit. The information on the stages of sleep chart might all seem academic at first. However, when you look at it carefully, you can see when disruptions occurred. You can tell at a glance if any stages of sleep are missing or if you are getting very little of one of the sleep stages. The chart is helpful for your doctor as well, because they can use it to determine what treatments might be most effective for you. A psychologist can refer to the sleep chart to help you find effective psychological techniques and practical strategies for getting a better night's sleep.

What Happens When You Don't Sleep? What Are the Sleep Deprivation Stages?

Sleep deprivation stages are usually listed by the number of hours you've been awake. Regardless of what is keeping you awake, you will eventually sleep, like it or not. The following stages of sleep deprivation are some of the things that happen to you as you become more and more sleep-deprived.


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After 24 hours - Your coordination, memory, and judgment are impaired.

At 36 hours - Inflammation in your body increases, which can cause heart disease or high blood pressure. Your hormones are affected. The earlier effects on coordination, memory, and judgment become more severe.

At 48 hours - You become disoriented and have involuntary microsleeps, sometimes without even realizing it.

At 72 hours - You hallucinate easily and frequently. Your cognitive processes are seriously affected in myriad ways, making every situation more difficult to understand and manage.

How to Solve Problems Resulting from Disturbed Stages of Sleep Cycle

Anyone who is having serious mental or physical health disorders that may be caused by sleep cycle disturbances needs to see a medical doctor to get help as soon as possible. Depending on the type of condition you have, you may choose to see your primary care physician, a sleep specialist, or your psychiatrist.

What do you do if you find out through careful observation or a sleep study that your sleep cycles are being disrupted? It might not seem very important if you haven't experienced any physical or mental health problems so far. Yet, those problems are likely to happen if you don't do something to correct your sleep patterns.


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If you've only experienced mild effects of sleep stages issues, you can begin now to resolve them before they become extremely serious. A psychologist can help you develop new strategies to get to sleep and stay asleep 7 to 9 hours as doctors recommend. A therapist can help you identify changes you need to make to your sleeping environment and routine. They can teach you psychological techniques for relaxing before you go to sleep, which may help you sleep more naturally in all 5 stages.

Licensed counselors are available through Better Help, a platform for professional counselors who work with patients via internet-connected smartphones, tablets, laptops, or desktop computers. Getting help at BetterHelp.com for sleep stages concerns as well as many other mental health issues is both affordable and convenient. The rewards come in better sleep and a happier and more productive waking life.


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