The Basics Of Sleep: Stages and Benefits

Written by Dr. Lynda Odoh - Anikwe on Wed, 13 September 2023

Key Highlights

  • In the early parts of non-REM sleep, brain waves slow down considerably; however, in stage 2 and stage 3, there are numerous quick bursts of brain activity.
  • In REM sleep, brain activity accelerates, showing markedly different types of brain waves.
  • Heightened brain activity is why REM sleep is known as the stage most associated with vivid dreaming.
  • REM sleep is thought to enable critical cognitive abilities, including memory consolidation, but non-REM sleep, even with reduced brain activity, is also believed to play a role in facilitating proper brain function while awake.

Prior to the 1950s, most people believed that sleep was a passive activity during which the body and brain were dormant. But it turns out that sleep is a period during which the brain is engaged in a number of activities necessary to life—which are closely linked to the quality of life.

What Happens In The Brain During Sleep?

Brain chemicals are very involved in our sleep cycle. Neurotransmitters are chemicals that help the nerves communicate. They control whether we're awake or asleep, depending on which neurons (nerve cells) they're acting on:

  • Neurons in the brainstem (where the brain and spinal cord meet) produce neurotransmitters called serotonin and norepinephrine. These chemicals keep our brain active when we're awake.
  • Neurons located at the base of the brain are responsible for us falling asleep. It seems these neurons turn off the signals that keep us awake.

Need for Sleep

Why sleep is important

Sleep helps us in many ways and thus we need it for:

  • Growth: In children and young adults, deep sleep supports growth. The body releases growth hormone during this type of sleep. The body also increases production of proteins, which we need for cell growth and to repair damage.
  • Nervous system function: A lack of sleep affects a person's memory, performance and ability to think clearly. If a person is severely sleep deprived, they may even experience neurological problems such as mood swings and hallucinations. Sleep also helps our nerve cells. They can repair themselves, so they function at their best. And certain nerve connections get a chance to turn on, strengthening our brain and thinking ability.
  • Survival: Studies in animals have shown that being deprived of REM sleep can shorten lifespans. Lack of sleep may harm the immune system, which protects us from infections.
  • Well-being: People who don't get enough sleep are at higher risk for developing various health conditions, including obesity, diabetes and heart problems.

The Stages Of Sleep

When a person is sleeping, his brain goes through natural cycles of activity. Throughout sleep, our brain will cycle repeatedly through two different types of sleep: REM (rapid-eye movement) sleep and non-REM sleep.

Non-REM sleep happens first and includes three stages. The last two stage of non-REM sleep is when you sleep deeply. It's hard to wake up from this stage of sleep.

REM sleep happens about an hour to an hour and a half after falling asleep. REM sleep is when you tend to have vivid dreams.

When you sleep, your body cycles through non-REM and REM sleep. The sleep cycle usually beings with stage 1 of non-REM sleep, then you pass through the other stages of non-REM sleep, followed by a short period of REM sleep. Later, the same cycle begins again at stage 1.

A full sleep cycle takes about 90 to 110 minutes. First REM period is short. As the night goes on, you will have longer duration of REM sleep and less of deep sleep.

What is Non-REM sleep?

The Stages Of SleepThree stages make up non-REM sleep.

Stage 1:

This stage of light sleeping lasts for five to 10 minutes.

  • Everything starts to slow down, including your eye movement and muscle activity. Eyes stay closed. If you wake up from stage 1 sleep, you may feel as if you haven't slept at all. You may remember bits of images.
  • Everything starts to slow down, including your eye movement and muscle activity. Eyes stay closed. If you wake up from stage 1 sleep, you may feel as if you haven't slept at all. You may remember bits of images.
  • Sometimes, you may feel like you're starting to fall and then experience a sudden muscle contraction. Healthcare providers call this motion hypnic myoclonic or hypnic jerk. Hypnic jerks are common and not anything to be concerned about as this occurrence is unlikely to cause any complications or side effects.

Stage 2:

  • This period of light sleep features periods of muscle tone (muscles partially contracting) mixed with periods of muscle relaxation.
  • Eye movement stops, heart rate slows down and body temperature decreases.
  • Brain waves become slower. Occasionally, you'll have a burst of rapid waves called sleep spindles.
  • Body prepares to enter deep sleep.

Stage 3:

  • This stage is deep sleep.
  • During this stage, your brain produces delta waves, very slow brain waves.
  • It's hard for someone to wake you up during this stage.
  • You have no eye movement or muscle activity.
  • If you're woken up, you may feel groggy and disoriented for a few minutes.

What happens during non-REM sleep?

During non-REM stages, our body builds bone and muscle, repairs and regenerates tissues, strengthens the immune system.

With age, a person gets less non-REM sleep. Older adults get less deep sleep than younger people.

What is REM sleep?

In REM sleep, brain activity increases again, meaning sleep is not as deep. The activity levels are like when you're awake. That's why REM sleep is the stage where a person gets intense dreams.

At the same time, major muscles (such as arms and legs) can't move. In effect, they become temporarily paralyzed.

Usually, REM sleep arrives about an hour and a half after you go to sleep. The first REM period lasts about 10 minutes. Each REM stage that follows gets longer and longer.

The amount of REM sleep you experience changes as you age. The percentage of REM sleep is highest during infancy and early childhood. Whereas, it declines during adolescence. There is further decline as you get older.

What else happens to the body in REM sleep?

Besides increased brain activity and muscle relaxation, body goes through a series of changes during REM sleep. These changes include:

  • Faster breathing
  • Increased heart rate and blood pressure
  • Rapid eye movement

Body's Built-in Sleep Controls

There are two main processes that regulate sleep: circadian rhythms and sleep drive.

Circadian rhythms are controlled by a biological clock located in the brain. One key function of this clock is responding to light cues, ramping up production of the hormone melatonin at night, then switching it off when it senses light. People with total blindness often have trouble sleeping because they are unable to detect and respond to these light cues.

Sleep drive also plays a key role: Your body craves sleep, much like it hungers for food. Throughout the day, your desire for sleep builds, and when it reaches a certain point, you need to sleep. A major difference between sleep and hunger: Your body can't force you to eat when you're hungry, but when you're tired, it can put you to sleep, even if you're in a meeting or behind the wheel of a car. When you're exhausted, your body is even able to engage in microsleep episodes of one or two seconds while your eyes are open. Napping for more than 30 minutes later in the day can throw off your night's sleep by decreasing your body's sleep drive.

How Genes Affect Your Sleep Clock

A few researchers recently identified a gene involved in the circadian regulation of sleep timing. When researchers removed this gene—called "wide awake"—from fruit flies, the flies experienced problems falling asleep and staying asleep.

A similar sleep gene exists in both humans and mice. Scientists continue to study this gene in hopes of understanding more about how processes within our cells affect our to sleep.

How To Maintain A Healthy Sleep Cycle

Maintain A Healthy Sleep Cycle


Getting in sync with your body's natural sleep-wake cycle, or circadian rhythm, is one of the most important strategies for sleeping better. If you keep a regular sleep-wake schedule, you'll feel much more refreshed and energized than if you sleep the same number of hours at different times, even if you only alter your sleep schedule by an hour or two.

Try to go to sleep and get up at the same time every day This helps set your body's internal clock and optimizes the quality of your sleep. Choose a bed time when you normally feel tired, so that you don't toss and turn. If you're getting enough sleep, you should wake up naturally without an alarm. If you need an alarm clock, you may need an earlier bedtime.

Avoid sleeping in even on weekends The more your weekend/weekday sleep schedules differ, the worse the jetlag-like symptoms you'll experience. If you need to make up for a late night, opt for a daytime nap rather than sleeping in. This allows you to pay off your sleep debt without disturbing your natural sleep-wake rhythm.

Be smart about napping While napping is a good way to make up for lost sleep, if you have trouble falling asleep or staying asleep at night, napping can make things worse. Limit naps to 15 to 20 minutes in the early afternoon.

Start the day with a healthy breakfast Among lots of other health benefits, eating a balanced breakfast can help sync up your biological clock by letting your body know that it's time to wake up and get going. Skipping breakfast, on the other hand, can delay your blood sugar rhythms, lower your energy, and increase your stress, factors that may disrupt sleep.

Fight after-dinner drowsiness If you get sleepy way before your bedtime, get off the couch and do something mildly stimulating, such as washing the dishes, calling a friend, or getting clothes ready for the next day. If you give in to the drowsiness, you may wake up later in the night and have trouble getting back to sleep.

Benefits Of A Healthy Sleep Cycle

1. Easier to sleep: When you were a child, your body probably had its own sleeping schedule for you to stick to every night. Then as you got older and got busier with real life, you soon forgot what your natural body clock was.

This would result in you having trouble sleeping at night. To eliminate common minor sleep problems, make sure you have a comfortable sleep environment, a healthful balance of nutrition and exercise, and frequently engage in relaxing activities before bedtime.

2. Creates a healthy sleep-wake pattern: A sleep schedule is the act of sleeping and waking up at the same time - otherwise known as a sleep-wake pattern.

Even if it's your day off or it's the weekend, your body will remember what time you should go to bed and what time shall you wake up. This way, you won't have any problems getting a good night's sleep at all.

3. Better stress levels and mood booster: When you have a sleep schedule, you won't have any trouble getting enough sleep at night. By the time you wake up, you will feel recharged and well-rested in the morning, thus getting you into a good mood.

Ensure that when you're stressed at work, don't bring it with you in your bedroom. Instead, do some relaxing activities such as yoga, reading a book, or taking a hot shower, so that stress won't disrupt your sleeping schedule.

4. Reduce the risk of heart diseases, stroke, and cancer: Studies have shown that people who don't get enough sleep are at a greater risk of heart diseases, stroke, and an even higher risk of cancer. Some of the systems that may be affected by sleep in ways that result in cancer risk include the brain, the production and regulation of hormones, the immune system, metabolism, and body weight.

Sleep may affect how cells function, adjusting their environment, or the signals that affect how they grow. Thus, it's best if you take your sleep schedule seriously to prevent fatal illnesses. If you think you've poor sleep hygiene and are experiencing symptoms of a disease, it's best to opt for an MRI scanning and a general body scan and detect any diseases at an early stage.


5. Avoid sleep disorders: Following a consistent sleep schedule can help you avoid sleep disorders such as insomnia, hypersomnia, sleep apnea, parasomnia, and others. The way you strive to maintain a balanced diet to stay physically fit and healthy, you need to do the same goes for your sleep schedule.

When you have a healthy sleep schedule, you won't suffer from these disorders and may put yourself in the best position to sleep peacefully at night.

6. Avoid the risk of obesity: It has been proven that people who have a short sleep duration tend to gain weight faster than those who get adequate sleep every night. Hence, it would result in obesity. If you're trying to lose weight, you must get quality sleep and stick to your sleep schedule. Aside from that, it's also known that people who get inadequate sleep tend to consume more calories.

This increase in calorie-intake may be due to increased appetite and unhealthy food choices. However, it may also only be from an increased time spent awake and the availability to eat. This is particularly true when the time awake is spent being inactive, like watching television and consuming snacks after dinner.

7. Maximize brain functions: Sleep is also vital for several aspects of your brain function. This includes your concentration, productivity, memory, cognition, and performance. Frequently depriving yourself of sleep will negatively affect all of the mentioned functions. Research also discovered that short sleep could negatively impact brain function aspects to the same degree as alcohol intoxication does.

Moreover, a healthy sleep schedule can improve your memory and optimize problem-solving skills. Whereas getting insufficient sleep can only impair your brain functions.

8. Improve overall health quality: Being consistent with your sleep schedule is not just about getting enough sleep every night. It's about enhancing your overall health quality. Your healthy sleep schedule can improve your immune system and even improve your physical performance during the day.


A lot happens in your body while you sleep; you cycle between REM and non-REM sleep. There are three phases of non-REM sleep. Each stage can last from 5 to 15 minutes. You go through all three phases before reaching REM sleep. REM sleep happens 90 minutes after you fall asleep.

As you get older, you sleep more lightly and get less deep sleep. Aging is also linked to shorter time spans of sleep, although studies show that you still need as much sleep as when you were younger. Few benefits of a healthy sleep cycle are decreased stress levels, reduced risk of obesity, sleep disorders & improved health.


Dr. Lynda Odoh - Anikwe

Dr. Lynda Odoh - Anikwe (M. B. B. S) is a MPH  candidate at the University of Manchester. Dr Odoh is also currently a member of the Society of Lifestyle Medicine Nigeria, and aiming to get certified by the International board of lifestyle medicine as a Lifestyle Medicine Physician by the last quarter of 2022.

Did you like our Article?





Not Sure




Leave a Comment

Our team of experts frequently monitors developments in the health and wellness field, and we update our articles when new information becomes available.

Current Version

Sep, 13 2023

Written By

Dr. Lynda Odoh - Anikwe

Aug, 01 2023

Written By

Dr. Lynda Odoh - Anikwe