Understanding the Stages of Sleep & How It Affects Your Body: Do You Really Need 8-9 Hours of Sleep? (Updated for 2021)

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To give you a quick answer, yes, you do need 8-9 hours of sleep every night. More even, if you’re younger. Newborns, for example, require up to 17 hours of sleep per day to develop well. But as newborns grow into kids, teens, and enter adulthood, sleep is still crucial.

It’s not hard to understand the importance of sleep. We all know that sleeping well and being fully rested is essential to our mind and body’s overall health. Everyone has probably had an interesting story to tell about the consequences of being sleep deprived – especially new parents, people working night shifts, or students up all night studying for exams.

Regardless of why you may be sleep-deprived, it’s still important to try and get the recommended hours of snooze time. So, this comprehensive sleep guide aims to help you understand how sleep works and what it does to your body. We’ve also covered tried-and-tested tips for better sleep as well as helpful information on sleep health, sleep disorders due to trauma or depression, and some bonus topics on COVID-19-related sleep information. At the end of this article, you’ll know so much about sleep that you’ll surely be encouraged to catch restful Zzzz’s at night.

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Main Points

How Much Sleep Do You Need?

Getting the appropriate amount of sleep is critical to your health. It improves the function of your organs and tissues while also preparing your brain functions for the next day. The amount of sleep you need differs depending on how old you are. It also plays a different role depending on each specific stage of development. 

See our guide below for you to know exactly how much sleep you need from ages 0 to 64 years+ old and also check our complete sleep guide for other information.

Newborn (0 - 4 months)

Recommended amount of sleep: 14 – 17 hours

0Since newborns are brand new humans, they do not have a circadian rhythm yet, and as such, they go through several phases of sleep. These phases typically last between 2.4 and 4 hours. 

But why do newborns, who are so tiny, need so much sleep? The answer is simple: newborns are recommended to sleep anywhere from 14 to 17 hours because they need to become bigger and stronger. While we associate sleep with resting and recharging, for newborns, sleep means something else entirely.

While asleep, their little bodies are busy at work to ensure that the food they take in (formula or breast milk) is turned into new muscles, fat, bone mass, tendons, and everything their fragile body needs to grow.

Infants & Babies (4 months - 1 year old)

Recommended amount of sleep: 12 – 15 hours

1

This is when the brain begins forming distinct sleep stages. Infants generally start developing more distinct sleeping routines at this age, including 2 to 3 naps per day. An infant typically sleeps 12 to 15 hours distributed throughout the day into night.

In the same way that newborns need sleep to grow, infants need it just as much. From 4 to 12 months old, babies need to meet certain milestones to ensure that they are growing well. For example, their first smile, first word, first tooth, first time to sit up, first time to roll over – these are some common developmental milestones that each baby needs to meet. And sleep, along with the proper diet, love, and affection of their caregivers, will help them develop into healthy toddlers.

Toddlers (1 year - 2 years old)

Recommended amount of sleep: 11 – 14 hours

2By the time a child is a toddler, their sleeping patterns are fully developed. They spend a quarter of their time in deep sleep and another quarter in REM. This is a higher percentage of time than we spend as an adult. Toddlers are recommended to sleep between 11 and 14 hours per day, including one to two naps. Also, this is when they stop having bodily movements during REM.

In terms of health and development, sleep affects many aspects of a toddler’s overall growth. It’s so crucial that getting too little of it will show almost-immediate effects on toddlers. For example, you’ll find that underslept toddlers are more easily agitated, have more tantrums, and, in some extreme cases, more sickly.

Following a strict bedtime routine will allow toddlers to sleep better, deeper, and longer, positively affecting their height and weight, including their emotional and mental well-being.

Preschool Children (3 - 5 years old)

Recommended amount of sleep: 10 – 13 hours

3Preschool children need slightly less sleep than toddlers, and as such, their need to nap around twice a day will subside around the ages of 3 and 4 to just once a day. They continue to have deep sleep for a higher portion of time, but their sleep patterns become closer to that of adults. 

Active toddlers should sleep at least 10 to 13 hours per day. This can be distributed to about 8 – 11 hours at night and 2 hours worth of naps during the day.

School-aged Children (6 - 13 years old)

Recommended amount of sleep: 9  – 11 hours

6Sleep is crucial for school-aged children who tend to have more activities compared to their toddler years. From homework to after-school activities like sports or music lessons, school-aged children need as much rest as they can get. 

This is why it’s recommended for them to sleep from 9 to 11 hours per day. Their deep sleep remains high, at around 20 to 25% of their daily sleep. This type of sleep is essential for growth and development especially for children with special needs. You can jump to the sections below to learn more about the stages of sleep.

It can be hard to tell whether your school-age child is getting enough sleep. Unlike older kids, tired school-aged children tend not to slow down. Instead, they become more active. This is why a child might refuse to go to sleep at night. Some reasons why your child may be having trouble sleeping are sleep apnea and ADHD. These two conditions tend to correlate because they both occur in the same part of the brain.

The best way to ensure that your school-aged child gets the sleep they need is to continue maintaining a consistent bedtime routine and avoid taking any food or drink with high sugar content 2-3 hours before bedtime.

Adolescents (14 - 17 years old)

Recommended amount of sleep: 8 – 10  hours

7When a child enters their teen years, their circadian rhythm changes, they go to bed later and tend to wake up later. However, a teen should be getting 8 to 10 hours of sleep each night, but due to early school times and other activities, sleep deprivation is prevalent among the teen years.

In fact, many experts say that sleeplessness among teenagers raises an alarming concern towards their mental and emotional well-being. For example, a study participated by 28,000 high school students in Virginia found that every hour of sleep deprivation predicted potentially disastrous results: a 38% increase in depression symptoms, a 23% increase in substance abuse, and a 58% increase in suicide attempts.

So, while it might be easy for us to forget that teenagers still need the right amount of sleep, we all need to work harder to remind our teenaged friends and family to never forget that sleeping well can heal the mind and body. There are many tried-and-tested ways for teens to get the sleep they need, including learning how to manage their time and not overloading their schedules with too much activity.

Parents and caregivers can also play an active role in encouraging sleep in teens, such as connecting rest with motivators like extending car privileges or other similar rewards. Making the connection between good sleep and better outcomes during exams or other school activities will also help teens see that sleeping well is important.

Young Adults (18 - 25 years old) & Adults (26 - 64 years old)

Recommended amount of sleep: 7-9 hours

8As teenagers enter young adulthood, their circadian rhythm begins adjusting back to normal. Going to bed earlier becomes more natural, making early start times much more manageable. People of these ages generally need 7 to 9 hours of sleep each night.

For fully-grown adults ages 26 years old and above, the circadian rhythm continues drifting back to an earlier bedtime. The need for sleep remains between 7 and 9 hours. As you age, less sleep is necessary to feel well-rested.

It’s important to note that the recommended sleep times for young adults and adults vary because everyone has different needs. According to Dr. Michael Breus, sleep specialist and author of “The Power of When,” the average adult requires an average of about 7.5 hours of sleep and not the proverbial 8 hours. Some can thrive and function on about 6+ hours of sleep, while others need more. Dr. Breus says our sleep drive, much like our hunger drive, is different for each of us. 

As such, we can’t compare our sleep needs with that of another individual. To determine exactly how many hours of sleep you need, Dr. Breus recommends using the following method:

Note that this method won’t work if you’re a night owl or a very early riser.

Older Adults (26 - 64 years)

Recommended amount of sleep: 7-8 hours

9In an ideal world, the elderly would get 7 to 8 hours of sleep, but this is not the case for many. Due to a common syndrome called Restless Legs Syndrome (RLS), many have trouble sleeping. This affects 13% of men and 35% of women. In addition to this, it can be difficult for the elderly to get sleep due to illness or medication. Both of which make uninterrupted sleep difficult.

Still, there are many ways for older adults to get the right amount of sleep: staying active during the day by doing light exercises, joining a club or pursuing hobbies, getting the therapy/medical help needed, and investing in the right mattress, bedding and sleep accessories for seniors. Check our sleep guide for seniors for more information.

Who made these sleep recommendations?

Organizations recognized by the medical community such as the American Academy of Sleep Medicine (AASM) or the Sleep Research Society (SRS) publish sleep recommendations based on age/development both for adults and children. These studies coincide with findings from expert researchers or panels composed of professionals from different fields related to sleep health.

What Happens If You Don't Get Enough Sleep?

Unlike eating habits that can be changed depending on the person’s need, sleep is, unfortunately, one of the few things in life that is something that’s difficult to adjust or make up for. For example, just because you’re busy today doesn’t mean you can simply cut down on your sleep without expecting any consequences. If you try to sleep less, your judgment will be affected, you will be less alert, and you will be moodier than usual.

Here’s a list of what will happen if you don’t get enough sleep:

If you are chronically sleep-deprived, here are other health risks that you potentially face:

Also, if left untreated, sleep deprivation can lead to more severe sleep disorders such as:

Other extreme forms of sleep disorders can even become a consequence of sleep deprivation, such as:

What is COVIDsomnia?

In the time of a pandemic, sleep should be made more of a priority than it ever was. But it’s also understandable that, globally, people are finding it hard to sleep. It’s become a worldwide sleep deprivation phenomenon that sleep neurologists have aptly named it “COVIDsomnia.”

In a nutshell, COVIDsomnia is a form of insomnia generally caused by COVID-19, whether directly or indirectly. Some people who already have chronic insomnia are experiencing more severe sleep issues, while those that did not previously have any problems with falling asleep are suddenly experiencing it now.

If you or a loved one is experiencing sleep health issues related to the challenges of coping with daily life during this pandemic, then you should seek the proper treatment. You can find tips and resources in our COVID-19 sleep guidelines.

What Happens If You Get Too Much Sleep?

Have you ever overslept and felt “drunk” or just a bit muddled before getting up? According to experts, “sleep drunkenness” is an actual condition after oversleeping – typically over 9 hours. It’s aptly termed since anyone who experiences sleep drunkenness will feel groggy and disoriented. 

While babies, children, and teens thrive on more than 8 – 9 hours of sleep, it’s not the same for adults. In fact, sleeping too much can lead to the same health risks as sleeping too little:

How Do We Know If You Are Getting Enough Sleep?

Knowing if you are oversleeping or undersleeping all depends on how it is affecting your daily life. Sleeping too much or too little from time to time is expected. After all, our days are never the same. Sometimes we have to crunch deadlines and miss a couple of hours of sleep or, we might just need to get up early to pick up someone at the airport. 

Below, we’ve listed some common signs that indicate whether you sleep too much or too little.

Signs You Are Undersleeping

Signs You Are Oversleeping

While the above are common signs that you experience if you sleep too much or too little, sometimes these can also be a symptom of something deeper. This is why if your sleep patterns are erratic lately and it’s negatively affecting your work or your life in general, it’s best to seek the advice of a sleep health professional.

What Happens When We Sleep?

Now that we’ve covered exactly how much sleep you need to get and how to tell if you’re sleeping too much or too little, plus some simple tips to make your night better, it’s time to dig a little deeper and find out exactly what happens while our eyes are closed.

Why Do We Sleep?

The question of why we sleep has been debated for a long time. Whether it started with the dream theories of the ancient Greeks and Romans or continued with the recent era of brain imaging techniques, there are still many unanswered questions either way.

According to Dr. Michael Halassa, a neuroscientist at New York University, “It’s obvious why we need to eat, for example, and reproduce … but it’s not clear why we need to sleep at all.”

For the most part, we know what happens to our bodies if we don’t sleep, but even the most experienced sleep scientists cannot pinpoint exactly why. There are, however, a few theories that attempt to explain the reasons why our bodies go “offline” for a few hours of the day. Researchers, however, all seem to agree that sleep plays a vital role in the brain’s plasticity.

Brain plasticity (or neuroplasticity) refers to the brain’s ability to reorganize itself. Without this particular feature, the brain would be unable to “re-wire” itself after brain damage or develop from infancy to adulthood. Research findings are as of yet fragmentary, but results do show that sleep is linked to the brain’s plasticity. 

What we do know, though, is what happens when we sleep. The following section discusses the 5 stages of sleep and why each stage is vital to our overall sleep health.

What Are The 5 Stages of Sleep?

It was not until the 1950s and 60s when sleep stages became truly defined. In 1953, availability for an appropriate imaging technique finally became available. Where the rapid rolling of the eyes during sleep was observed, it was then referred to as REM (Rapid Eye Movement). It was found that REM is the stage where you dream. When this research was published, it quickly brought on interest in popular American culture.

Several years later, they would define the stages of sleep based on brain waves and breathing. There are three more stages in our sleep cycle, including stages 1, 2, and 3. There is a debated fourth stage too, which is characterized by extremely slow brain waves. However, it is so similar to stage 3 that it can generally be lumped together into one stage of deep sleep.

Sleep cycles make up the duration of our sleep. Once we shut our eyes, there are two types of sleep. These are:

We pass through 3 to 5 cycles each night, with each one lasting anywhere from 90 to 110 minutes. The shortest cycle of the night is the first to pass through 3 to 5 each night. 

Differences in brain activity and roles characterize each stage of sleep. They are each important in their way and help make you a healthier person. Deep sleep plays a role in muscle and brain regeneration, while REM restores your mind. Experts also say that REM perhaps plays a role in “cleaning up” irrelevant information that builds up in your brain during the day. Additionally, recovery sleep is necessary when sleep is put off for a while.

The 5 Stages of Sleep

Quick Overview

young female sleeping peacefully bed morningThese 5 stages include the four stages of NREM and REM itself. The stages of NREM follow a pattern of getting increasingly deeper. This includes lower heartbeat and blood pressure. Another symptom of deep sleep is alpha brain waves.

N1 is the lightest sleep, sometimes acting as a transition between wakefulness and rest. N2 is a deeper form of light sleep while taking up 50% of your total sleep time. Finally, there is deep sleep. These are the N3 and N4 stages of sleep. They are about identical, with slightly slower brain waves during N4.

How do Sleep Patterns Cycle While You Sleep?

Sleep patterns change cyclically throughout the night. One does not switch to REM immediately after the N3 stage of sleep. Instead, the body must adjust to much more rapid brain waves. So a cycle would flow as follows: N1, N2, N3, N2, N1, REM. This means that most of your sleep is spent in N2, with only 10 – 15% in restorative sleep. However, more recovery sleep is necessary when rest is put off for a while.

Let’s have a closer look at each stage of sleep:

Stage 1 - Shallow Sleep

Typically, after hitting your pillow, stage one sleep follows within moments. This first stage of sleep is shallow and ordinarily will not last more than 7 minutes. As the lightest of NREM sleep, outside distractions often cause awakenings.

The brain rocks your body to sleep with high amplitude theta waves. These are very slow brain waves, which relax your entire body. Sometimes other symptoms such as hypnic jerks (abrupt muscle spasms), or a sense of falling can occur.

Stage 2 - NREM Sleep

This is the first stage of defined NREM sleep. (Though it is still considered a form of light sleep). You become less aware of your surroundings, making awakenings less common — the body temperature drops, followed by a decrease in breathing and heartbeat.

The brain begins producing rhythmic brain waves known as sleep spindles and K-complex structures. These brain waves are not fully understood but are believed to be a signal of stable sleep. Some theories claim that they are similar to a sound machine. They make patterned rhythms to protect the body from awakenings.

Stages 3 & 4 - Deep, NREM Sleep

This is the deepest of NREM sleep. The brain produces delta (slow) waves, creating the most restorative stage of your sleep cycle. Awakenings during this stage are rare and would cause sleep drunkenness if you ever do wake up. This means you would be in such a state of grogginess you won’t be aware of what’s going around you and perhaps fall  right back to deep sleep.

Parasomnias can happen during this stage. These are characterized by undesirable behavior, showing up in the forms of night terrors, sleepwalking, and bedwetting. A sudden arousal from deep sleep often causes this. The motor centers, but not the higher centers, are awakened.

Deep sleep is very restorative. The brain resets for learning the next day. The immune system restores itself, and human health hormones are released. Bodybuilders once used a drug called GHB to lengthen their time in deep sleep. They found that the restorative properties were beneficial for muscle building and repair.

Stage 5 - REM Sleep

This is when most of your dreaming occurs. It is known as Rapid Eye Movement, primarily because of the quick motion of the eyes during this part of sleep. Brain waves are just as rapid as during the day, often “replaying” the events of that day. The body is temporarily paralyzed during this stage, making it impossible to act out the depictions in your dreams.

During this stage, the heart rate and blood pressure increase, and the body loses its ability to stabilize its body temperature or thermoregulation. When awakened during REM, sleep inertia  (worn out syndrome) occurs. This causes a high sense of sleepiness which can sometimes last for a considerable time after you wake up.

At the start of the night, less time is spent in REM sleep. However, about halfway through, REM sleep takes on much more of a priority. The NREM sleep becomes lighter, and the REM sleep becomes longer in duration. Usually a person experiences 3 – 5 REM stages throughout the night.

How Do You Create A Great Sleep Environment At Home?

To create an environment that’s best for sleep, you must focus on your bedroom. Often looked at in the aspect of interior design more than sleep comfort, your bedroom should be a haven for deep, restful sleep. In other words, it shouldn’t just be something nice to look at, but it should also ideally be cozy, comfortable, and only filled with things that will help you sleep well. 

If you don’t have the budget for a huge renovation, then that’s not a problem. The important thing is that your bedroom is neat, clean, and organized. When cluttered with other distractions like a desk for work, dirty laundry, books, or plates of unwanted food, your bedroom will no longer become somewhere for you to relax after a long day. This could be most challenging for the sleep deprived American homeless.

Here are some easy, helpful ways to make your bedroom perfect for sleep:

Tips for Getting a Better Night’s Sleep

young sleeping woman alarm clock bedroom homeMaking sleep a priority will change your life for the better. Try these tips below:

Conclusion

A great night’s sleep doesn’t have to be a puzzle. It can be as simple as taking the time to prioritize it. Make a schedule, take time to relax, and exercise throughout the day. There is an abundant amount of solutions for insomnia, and it begins with right now. Choose to make this change because you deserve it.

More importantly, understanding how sleep works will also give you clearer insight on why it’s so critical to your overall growth hormone, health, and well-being.

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