The energy we feel when we're awake is often related to how much sleep we get at night.
We can all relate to the dreaded feeling of taking on the day after a night of poor sleep. Your body feels worn out, and your brain is full of fog.
During sleep, our body works to support and maintain our physical health and healthy brain function.
In a sense - your body recharges and repairs itself during this time.
Whether you’re striving to perform and feel your best with sports, work, or family life - sleep plays a critical role.
But, how much sleep do we really need?
When we asked our members the common health myths and practices they believed in - getting 8 hours of sleep every night was amongst the top ten.
But, is this true?
Does it really matter how many hours of sleep we get?
Is quality or duration of sleep more important?
And, can age affect how much sleep is optimal for our health?
We’ll be discussing all these questions and getting to the bottom of the idea that we need 8 hours of sleep every night to be at our best!
How much sleep do I need?
According to the National Sleep Foundation, the average adult needs about 7-9 hours of sleep every night. However, many factors can affect how much sleep you need, including age, pregnancy, your level of physical activity, and prior sleep deprivation (sleep deficit). We'll go into that later in this article.
If you get between 7 and 9 hours of sleep most nights, you'll spend about one-third of your life sleeping. However, keep in mind that the time you spend sleeping isn't wasted time. Your body is getting a lot of work done while you're sleeping. If you get high-quality sleep—and enough of it—you'll be healthier, more energetic, and more productive when you're awake.
But sleep duration is only part of the equation. Sleep quality matters just as much when it comes to whether or not your sleeping hours are actually restorative. The key is to progress through the four stages of the sleep cycle multiple times every night.
Genetics also plays a role in how much sleep you need. A 2009 study found that some people have a mutation in the DEC2 gene. These people can function efficiently on very little sleep. In fact, people with this mutation are well-rested after just 6.25 hours of sleep per night.
In 2019, a second short sleep gene was discovered when researchers at the University of California, San Francisco identified 50 families whose members require less than 6.5 hours of sleep per night. The research team used whole exome genome sequencing to study three generations of naturally short sleepers in one of these families and found a rare mutation of a gene that was being passed down in the family's DNA.
People who have these specific gene mutations are called "efficient sleepers." Magaret Thatcher, the former British prime minister, famously needed only four hours of sleep to feel well-rested and energetic. Researchers suggest that Thatcher probably had one of the gene mutations. However, most of us aren't this lucky. Less than 1% of humans have one of these mutations, so most of us need 7-9 hours of sleep to function at our best.
Quality or duration?
First, we should understand the difference between sleep quality and duration.
Whether you’ve had nights of tossing and turning or nights where you’re waking up often. Not all of our time spent trying to sleep is of good quality.
According to the nationwide research team - assessing sleep is better done using quality of sleep as a measurement rather than using the duration.
But, what does quality sleep even mean?
How can we measure the quality of our sleep?
The National Sleep Foundation states that there are generally 4 aspects used to measure the quality of sleep:
- Wakefulness: which is the amount of time you spend awake after first falling asleep
- Sleep latency: this refers to the amount of time it takes you to fall asleep
- Sleep efficiency: the time you spend sleeping while lying in bed
- Sleep waking: how many times you wake up during your sleep
Becoming aware of all four parts of your sleep quality will allow you to better measure if you’re having a good sleep.
Do you wake up in the middle of the night?
Do you have trouble falling asleep?
These are all questions we should be asking ourselves when trying to figure out how much sleep we really need.
But, how come?
Why does it matter?
8 hours of quality sleep is much different from 8 hours of poor quality of sleep.
In fact, you feel the difference the day after.
Those days when we wake up feeling energized and satisfied with our sleep are generally days we can say we had a good quality sleep.
This brings up the point that when we refer to the hours of sleep we get a night, we’re referencing good quality sleep, not poor quality sleep.
But, the question still remains - how much sleep do we really need?
How many hours of sleep by age?
I’m sure we can all agree that age plays a role in the amount of sleep that’s necessary for optimal health.
When we were infants if we weren't crying or eating we were sleeping, and during our teenage years sleeping in felt like the greatest thing ever!
During infancy, the recommended number of sleep is as much as 16 hours a day! But, as we grow up the recommended time spent sleeping begins to lessen and lessen.
- From the ages of 3-5, it’s recommended we sleep 10-13 hours a day
- From the ages of 6-12, it’s recommended we sleep 9-12 hours a day
- From the ages of 13-18, it’s recommended we sleep 8-10 hours a day
- Then, from adulthood onward, it’s recommended we sleep 7 or more hours a day
Other than age, there are other factors that can affect our sleep patterns.
How much sleep we need can also be affected by things like:
- Sleep quality
- Physical activity
- Reaching older age
- Previous sleep deprivation
For example, your body may need 7 hours of sleep, but when you only sleep for 5 you create 2 hours of sleep debt.
This is why some people decide to nap, go to bed earlier some nights, or even sleep in on the weekends!
These approaches may provide temporary recovery and energy. But, research suggests that 1 hour of sleep debt takes a total of 4 days to recover to your optimal level.
This means it’s better in the long term for you to do your best to maintain a sleep schedule that fits your lifestyle.
The general guidelines provided by the NIH say from 18 years old and onward we should be getting 7-8 hours of sleep per night.
What is the sleep cycle?
The sleep cycle—sometimes referred to as the sleep-dream cycle, ultradian sleep cycle, or REM-NREM cycle—is the period of time it takes to transition through the four stages of sleep, which we'll define below.
A sleep cycle takes between 90 and 110 minutes, but can extend to up to 120 minutes. However, like all aspects of sleep, the sleep cycle duration varies depending on various factors. For example, the sleep cycle for infants lasts about 50-60 minutes.
If you sleep 7-9 hours at night, you'll go through between four to six sleep cycles.
Sleep cycles can be affected by a number of different things, including some medications. To encourage a healthy sleep cycle, try some of these things:
- Turning off all artificial lighting sources
- Practicing good sleep hygiene
- Relaxation techniques or meditation
- Avoiding caffeine in the afternoon and evening
Let's learn more about the four stages of sleep that make up the sleep cycle.
What are the four different types of sleep?
Sleep is divided into four stages. The first three stages are NREM sleep, and the fourth stage is REM (rapid eye movement) sleep.
The acronym NREM stands for "non-rapid eye movement," and the acronym REM means "rapid eye movement." NREM sleep is abbreviated by the letter N, with numbers representing the stages.
- Stage 1: N1 (NREM - drowsiness and light sleep)
- Stage 2: N2 (NREM - light to moderate sleep)
- Stage 3: N3 (NREM - deep sleep, delta sleep, or slow-wave sleep)
- Stage 4: REM (rapid eye movement or REM sleep)
Note that many experts cite five sleep stages, with two stages of deep sleep. However, the majority of sleep scientists focus on the four stages, so we're using the sleep stage guidelines established by the Sleep Foundation for this article.
Let's do a deep dive into what these four sleep stages mean.
Stage 1: N1 (drowsiness and light sleep)
Duration: 1-7 minutes
When you're in sleep stage 1, you drift from wakefulness to sleep. This light NREM sleep doesn't last for long. During stage 1, you begin to relax and dream, but you may twitch occasionally as you transition to stage 2.
During this stage, your body isn't fully relaxed, but brain and body activities start slowing down. If you're not disturbed, you will move quickly into state 2 of the sleep cycle.
Stage 2: N2 (light to moderate sleep)
Duration: 10-25 minutes
While still light sleep, stage 2 of the sleep cycle has you drifting into steadier sleep. As your heartbeat and breathing slow down, your muscles begin to relax. During this time, your body temperature decreases, and your brain waves become less active.
In this stage, brain activity begins to slow, but you will still have short bursts of activity that help your body resist being awakened by external stimuli. Throughout the night, stage 2 can become longer during sleep cycles. You spend about half your sleep time in N2 sleep.
Stage 3: N3 (deep sleep, delta sleep, or slow-wave sleep)
Duration: 20-40 minutes
The deep sleep stage of the sleep cycle lasts for up to 40 minutes, and it's more difficult for someone to wake you up when you're in this stage. Your breathing rate, muscle tone, and pulse rate decrease during N3 sleep, and your body begins to further relax.
Stage 3 is also known as delta sleep because of the identifiable patterns of brain activity. Another name for this stage is slow-wave sleep (SWS).
Deep sleep is critical to getting restorative sleep. This stage allows your body to recover and grow. Stage 3 also boosts your immune system and impacts some of your other bodily processes.
During the first half of the night, you spend more of your sleep time in deep sleep. Throughout the night and subsequent sleep cycles, deep sleep stages get shorter.
Stage 4: REM (rapid eye movement, REM sleep)
Duration: 10-60 minutes
Brain activity picks up during REM sleep, coming close to the same as waking hours. However, your body also experiences a temporary muscle paralysis called atonia. There are two exceptions to atonia: the muscles that control breathing and the eyes. Although your eyes are closed, they can also be seen moving quickly, and that's where the name "rapid eye movement" comes from.
The REM stage is believed to be highly associated with cognitive functions such as learning, memory, and creativity. During REM sleep, most people have vivid dreams because of increased brain activity, but they’re more common in NREM stages.
In most circumstances, you don't enter REM sleep until you've been asleep for approximately 90 minutes.
REM stages get longer throughout the night, particularly during the second half of the night. The first REM stage might last for just a few minutes, and later stages can last for about an hour. REM stages make up about 25% of sleep in the average adult.
Why is deep sleep so important?
The effects of sleep deprivation are well-known, and as we explained earlier, the quality of your sleep is as important as the quantity. All sleep stages are necessary, but deep sleep specifically offers numerous mental and physical benefits.
Deep sleep starts between 20 and 30 minutes after you first doze off, and it's this restorative sleep that dominates the first half of your sleep. Deep sleep lasts for up to an hour at a time, then you drift into deep sleep again approximately every 90 minutes.
Deep sleep is the most restorative sleep, and it's when we produce most of our growth hormones. For children, this is what helps them grow and develop. However, for adults, growth hormones are involved in youthfulness.
Also known as slow-wave sleep (SWS), deep sleep strengthens our bones and muscles, keeps our immune systems optimizing and functioning, helps us prevent injury, and contributes to many other important bodily functions. Equally important, if we're injured, deep sleep helps with recovery.
This sleep stage has been shown to have potential importance in regulating glucose metabolism, and elite athletes value deep sleep because it helps them replenish their energy stores. Researchers believe that deep sleep is important for memory and cognitive function and that it plays a significant role in motor skills, language learning, and brain development.
Signs you might not be getting sufficient deep sleep
If you are experiencing any of these issues, you may not be getting enough deep sleep.
- Reduced attention and alertness
- Hitting the snooze button repeatedly
- Cognitive fogginess
- Feeling drowsy
- Lowered libido
- Cravings for food high in calories
- Dozing off when it's not convenient, such as at your desk
- Slow reaction time (increased risk of having accidents)
- Increased anxiety
- Trouble forming new memories and learning
When you wake up, you should feel refreshed and alert. If you don't, you may not be getting enough sleep or your sleep may be lower in quality than it should be. Conditions such as general sleep disorder and obstructive sleep apnea also affect our sleep quality. In total, about 13-23% of your sleep should be deep sleep. For most people, this equals to between 1 and 2 hours every night for deep sleep.
What are the long-term effects of not getting enough deep sleep?
In addition to the issues listed above, chronic sleep deprivation has been linked to other serious health conditions. For example, if you don't get sufficient deep sleep, your immune response to vaccines may be weakened.
One of the roles deep sleep plays is eliminating waste products that are potentially harmful from the brain. For this reason, long-term deep sleep disruptions may drive the advancement of such neurological conditions as Parkinson's and Alzheimer's disease.
Because sleep deprivation increases our appetites for high-calorie foods, a shortage of slow-wave sleep may contribute to insulin resistance, which often manifests as heart disease and the development of type 2 diabetes.
How can I get more deep sleep?
If you're concerned that you're not getting enough deep sleep, there are some strategies you can employ to try to increase the quality of your sleep.
- Reducing the stress in your life
- Establishing sleep routines and rituals
- Eliminating caffeine in the afternoon and evening
- Using an eye mask for blocking light
- Using earplugs to block external noise
- Exercising regularly
- Creating a relaxing ritual or routine to wind down near bedtime
- Listening to pink or white noise
- Eliminating screen time for an hour before bed
- Using brainwave entertainment such as binaural beats
- Sleeping in a cool room
- Practicing sleep meditation
The bottom line - How much sleep do we really need?
We know that not all hours of sleep are created equal. There’s a difference between poor quality and high-quality sleep.
And, we know we can create a certain sleep debt in our lives causing us to fall behind.
This makes us more tired throughout the day, and we often try to catch up on sleep through different methods.
The general consensus for adults 18 years and older is that we should be trying to get 7-8 hours of sleep a night. Which is about 49-64 hours of sleep a week!
But, we know this isn’t always possible. Life can sometimes cause interruptions in getting that amount of sleep.
You should be doing your best to sleep 7-8 hours, but don’t beat yourself up if you can’t always do that. If you can’t sleep 7-8 hours a night, do your best to catch up on it, and try to start maintaining a consistent sleep schedule so you can prevent sleep debt!
Getting 8 hours of sleep each night is just one of the top ten health myths and practices our members said they believed in.
We’re just getting started with our health myth debunking series.
Stay tuned for upcoming blog posts where we're going to talk about more common health myths and if they’re even true!
Sleep your way to optimal health
All of the sleep stages are important to our health and well-being, with deep sleep being the most essential for staying healthy and feeling well-rested. If you're concerned you're not getting enough deep sleep, consider speaking with a healthcare provider or participating in a sleep study.
Evidation Members can earn points for tracking self-care activities such as walking, sleeping, food intake, and more. Download our app today to get started.