How Much Sleep Do You Need?

Research has shown that the optimal amount of sleep that we need each night is 8 hours. Yet, we still see people who can survive on less than 8 hours and those who need more than 8 hours. What is it that determines how much sleep we need to not only function but to thrive? We spend 1/3 of our lives sleeping. While we are asleep, the mind and body have a chance to rest, heal, take out the “trash” or toxins in the mind and body, and rejuvenate. It’s a function that is as necessary as breathing and eating. This guide will go over the mystery of sleep and how to know how much sleep you need.

Why do we sleep

The Stedman’s Medical Dictionary defines sleep as:

[su_quote cite=”Steadman Medical Dictionary”]“a natural periodic state of rest for the mind and body, in which the eyes usually close and consciousness is completely or partially lost, so that there is a decrease in bodily movement and responsiveness to external stimuli”.[/su_quote]

Sleep is an essential function for both our mental and physical health. Research has been done for years to determine the purpose of sleep, and it continues in an attempt to discover what else sleep does for us.

We have evolved over the centuries and our sleep requirements have changed with our environment. In the past, our sleep cycles followed a natural rhythm with the rising and setting of the sun. In the present, with people working so much in dark offices and then sitting up at night in front of a bright computer, phone, or TV screens, our sleep patterns have changed.

Sleeping in the past

Is it true that we slept better in the past than we do now? Having poor sleep patterns seem to be a modern issue due to so many having a sedentary lifestyle. We are glued to our phones and tablets, often staying up well into the night. Did our ancestors sleep better before all of this technology took over our lives?

A study was done on an indigenous tribe called the Hazda, found in Tanzania. You would think that these nomadic hunter-gatherers would have a fairly normal sleep routine that matches what our ancestors had before technology. What they did find was that sleep schedules differed widely amongst each individual and many woke frequently through the night. The study was run over a period of 3 weeks, and only once was there a time when all of the tribe members were asleep at the same time, for an 18 minute period. Now, it may be that this on and off sleep is down to ancient survival mechanisms that help protect them against threats in the night.

One main difference, when compared to western civilization, is that the tribe doesn’t have the usual anxiety, paranoia, and concerns regarding sleep that many people do.

Circadian Rhythm cycle

graph showing the flow of melatonin circadian rhythm
The flow of melatonin (Image from Luke Mastin)

As mentioned earlier, our lives are in sync with the 24-hour cycle of night and day. It’s not just in human beings either. Just about every form of life follows a circadian rhythm. Why is it that we are stuck in this cycle of 24-hours? As we have evolved over millions of years, this cycle has been firmly imprinted on our biological makeup, making it a genetic thing. You can see this with plants that have been kept in the dark. Their leaves will open and close as they would do when the sun rises and sets. It’s ingrained in all of us.

During the 1970s, scientists did experiments on fruit flies that helped them discover something crucial that kept this inner timeclock functioning. They discovered a gene that, like clockwork, had activity that followed this 24-hour cycle. It was referred to as the Period gene and its function was to release a protein that would build-up overnight. It would then be broken down during the day.

It was later found that human beings also had this gene that worked in a very tiny area of the brain, the suprachiasmatic nucleus. It’s a conduit that runs between the retina of the eye and the pineal gland in the brain. It’s what produces the flow of melatonin, also known as the sleep hormone. This is why, when it gets dark, we feel sleepy.

Does this SNC clock affect more than the brain?

The body has other secondary or peripheral circadian clocks
The body has other secondary or peripheral circadian clocks (image from Science Direct)

What is now referred to as the SNC clock, is the timekeeper of our entire body. Over the past decade, scientists have found that this gene is actually active in just about every type of cell in the body. Around half of our genes’ activity follows this circadian rhythm. Tests that were done on brain cells that were grown in a petri dish showed that those cells would start to organize themselves and begin to follow activity patterns that were similar to sleep patterns.

What the brain does while we sleep

REM sleep, brain activity looks similar to when you’re awake.
When you start to dream, your brain cells fire actively and randomly (Image Credit: WebMD)

When we go to sleep, our brains don’t just automatically turn off and stop working. What it does is generate 2 patterns of sleep, known as slow-wave and REM sleep. Slow-wave sleep is deep sleep, and REM, or rapid eye movement sleep, is when we dream. Around 80% of the sleep we experience is slow-wave sleep. This is when the brain waves are at their slowest, our muscles are relaxed, and our breathing slows down.

Evidence has shown that we need these periods of deep sleep for memory consolidation. This is how our recent experiences (in the past 24 hours) are moved to our long-term storage in the brain. Before this happens, the brain does a bit of a clear out of experiences that are not relevant, making room for the new, more relevant experiences. It was also found that the brains’ synapses shrink when we sleep. It’s the weaker connections that are removed, causing us to forget those experiences.

The other 20% of our sleep time is spent dreaming. Dream lengths can vary from a few seconds to an hour. It’s also been found that, as the night progresses, our dreams last longer. Most of these are forgotten quickly. The brain is highly active during these periods of REM sleep. Our heart rate increases, the muscles become paralyzed, and our breathing can sometimes become erratic.

How much sleep do we need

This brings us back to that question of how much sleep we truly need. In short, an adult needs between 6 to 9 hours of sleep a night. The optimal amount of sleep falls between 7 and 7 ½ hours, not including how much time it takes to fall asleep.

It’s not as simple as that though, and the amount a person needs can depend on a number of factors, such as health, age, mental activity, and any recent physical exertions. Genes also play a part in this, meaning that the amount of sleep you need can run in the family.

The recommended amount of sleep

A young child and senior male walking together on beach
As we age, our sleep needs (and the amount of sleep we actually receive) change significantly

According to the Healthy People initiative set out by the federal government, 18 to 21-year-old people should have 8 hours per night, and over 21’s should have 7 hours per night. The amount of sleep that we need changes as we move from childhood to adulthood. These are the recommended amounts each age group needs:

[su_table responsive=”yes”]

Age Daily Sleep Requirement
Infants under 1 year 16 to 20 hours of sleep
Children between 1-2 years old 14 hours of sleep
Children between 3-4 years old 12 hours of sleep
Children between 5-12 years old 10 hours of sleep
Teens between 13-19 years old 9 hours of sleep
Adults & Seniors 7-9 hours of sleep


Infants and children

The average infant will sleep between 16 to 20 hours a day. This will usually decrease to 12 hours when they reach 4. Also, their sleep schedule is spread throughout the day and evening. It isn’t until they reach 6 years old that they do most of their sleeping at night.

Teenagers and adults

As children grow, they need less sleep. Once they reach adolescence, they are down to needing only 9 hours and this happens mostly at night. Once they reach adulthood, the amount of sleep teenagers needed can vary, with some only needing 5 hours a night and others needing up to 10.


Many believe that you need less sleep as a senior. This isn’t the case though. In 2014, a study was done on seniors that showed they need the same amount of sleep as do young adults. The problem is that, as we age, the neurons that are responsible for sleep pattern regulation start to die off. This means that seniors will wake up whether they are rested or not.

It also causes many to suffer from insomnia.

How to tell how much sleep you need

It’s important that you pay close attention to your body in order to determine how much sleep you need. If you find that you feel drowsy during the day, even during less active periods, it means you haven’t had enough sleep the night before. On average, most people will feel a drop in energy levels in the early afternoon. However, if you find you are consistently falling asleep at this time, you need to get more sleep at night.

It’s not only about the quantity of sleep you get, but the quality as well.

People who tend to do fine on less sleep may do so because they are sleeping well.

However, research has shown that getting under 7 hours of sleep a night can have some negative impacts on our health and mental state. While it’s also been said that too much sleep isn’t good, there haven’t been any noticeable impacts on a person’s cognitive state of health as a result.

When you don’t get enough sleep

What happens to us when we aren’t getting enough sleep? Not sleeping for a night or two can have a big impact on us. Our sleep routines cannot be changed to reflect our life, meaning, just because you have a busy schedule, don’t expect that your need to sleep will fit itself in with that schedule. Trying to change what our body needs by forcing oneself to have less sleep will result in poor judgment, a slower reaction time, and memory issues. The only way to recharge is to get some decent sleep.

Catching up on missed sleep

Many feel that missing sleep is nothing to worry about because they can catch up on it later. The problem is, if you don’t have a consistent sleep pattern, you are always fighting to catch up on sleep. Trying to take a nap to catch up on sleep really doesn’t do a lot. We tend to recover about ½ of the REM sleep we have lost and some of the deep sleep.

Sleep deprivation

[su_pullquote]Power naps and microsleeps, which are very brief periods of sleep in someone who is, for the most part, awake, are another sign of sleep deprivation[/su_pullquote]

If you find that you normally fall asleep within a few minutes of laying down, you probably have a sleep disorder or are suffering from sleep deprivation. Power naps and microsleeps, which are very brief periods of sleep in someone who is, for the most part, awake, are another sign of sleep deprivation. Most people aren’t even aware of these short periods of sleep happening to them. We have become so used to being workaholics that feeling abnormal sleepiness is considered to be normal.

Are you getting enough sleep?

A tired overworked woman under the covers
Individual sleep needs may vary significantly

Most people aren’t even aware of how much sleep they may, or may not, be getting. Most people overestimate how much sleep they think they have had. If you want to find out if you are getting enough sleep:

  1. Start by taking note of what time you go to bed and what time you wake up. If you tend to not have trouble falling asleep, it probable takes between 15 to 20 minutes for you to fall asleep.
  2. Now, add those minutes to when you went to bed, and then subtract that from the time you have woken up.

Do you fall into the recommended 7 to 9 hours of sleep?

Signs of not getting enough sleep

You may get the recommended amount of sleep but still not feel rested. There are signs that can tell you whether you need more or less sleep. Many people who are sleep deprived aren’t even aware of it. You’re probably wondering how that is possible. The signs of sleep deprivation are quite subtle, and if you are used to not getting enough sleep, you probably don’t recall what feeling wide-awake is like. It isn’t really normal for you to feel sleepy when bored, to struggle during that afternoon period when energy is lower, or to doze off right after dinner. These are things that happen when you are sleep deprived.

Here are the main signs of being sleep deprived:

  • Can’t wake up on time without an alarm clock
  • Rely on using the snooze button
  • Find it hard to get out of bed in the morning
  • You feel sluggish during the afternoon
  • Tend to feel sleepy in warm rooms or during lectures and meetings
  • Feel drowsy when driving or after a heavy meal
  • Can’t get through the day without having a nap
  • You fall asleep in the evenings when relaxing or watching TV
  • Find you need to sleep in on the weekends
  • Find you fall asleep within five minutes of going to bed
  • You find you get irritated easily and are moody
  • You forget things more often and have poor performance

On the opposite side of the scale, these are signs you’re getting too much:

  • When going to bed, it takes over an hour to fall asleep
  • You normally wake before your alarm and still feel rested through the day
  • Your energy feels low during the day
  • You experience hypersomnia and/or feel depressed
  • You find you are gaining weight due to inactivity

Sleep and physical health

A lack of sleep can mess with levels of the hormones that control hunger - leptin and ghrelin.
A lack of sleep can mess with levels of the hormones that control hunger – leptin and ghrelin.

[su_pullquote]When deprived of sleep, these toxin levels rise and can cause symptoms linked to Alzheimer’s.[/su_pullquote]

A cumulative lack of sleep can lead to some long-term health issues, with links being found to diabetes, obesity, dementia, and heart disease. This seems to affect people who do night shift work more than others. A review of several existing studies found that those who permanently worked on night shifts were nearly 30% more likely to become overweight or develop obesity in comparison to those working a rotating shift. It also showed a rise of 41% of stroke and heart attack risk. It’s been proven that sleep deprivation alters our body’s metabolism, as well as the balance between muscle mass and fat.

Another study has shown that sleep deprivation may play a role in developing Alzheimer’s disease. During normal sleep, our brain cleanses itself of proteins that are linked to Alzheimer’s, known as beta-amyloids. When deprived of sleep, these toxin levels rise and can cause symptoms linked to Alzheimer’s.

Shift work and sleep

Back in the 1930s, Nathaniel Kleitman, an American scientist, performed his own study on the body clock. He spent 32 days in Kentucky’s Mammoth Cave, located 42 meters underground. He lived in complete isolation during that time and had no access to external indications of night and day. He chose to adopt a 28-hour day. He had rigid schedules around the time he went to bed and mealtimes, which were sent down a shaft via a bucket. However, he found he was unable to adapt to this 28-hour cycle, only feeling awake when the times that were assigned as 2daytime” occurred. This was set to be in sync with the outside world. During the experiment, Kleitman’s body temperature continued to follow close to a 24-hour cycle.

A large number of shift workers are faced with similar issues, especially those who have irregular shifts. It’s an issue that has only recently been taken seriously.

Myths about sleep

Oddly enough, there are many myths about sleep that so many believe but that aren’t really true.

#Myth 1 Your daytime functioning won’t be affected by just one hour less of sleep.

While you may not feel sleepy during the day, losing just one hour of sleep will affect your ability to respond quickly and think clearly. It can also compromise your energy balance, cardiovascular health, and your ability to fight off infection.

#Myth 2 Your body can quickly adjust to different sleep schedules.

Yes, most people are able to adjust their biological clock, but by one an hour or two max. It can take some people up to a week for their body to adjust in situations like switching from a day shift to night shift or traveling across time zones.

#Myth 3 Getting extra sleep at night will stop you from excessive tiredness during the day.

It’s not just about the amount of sleep you get, it’s also about the quality. Some people can sleep up to 9 hours at night and wake not feeling well-rested. This is because their sleep quality is poor.

#Myth 4 You can catch up on lost sleep during the week by sleeping more over the weekend.

This can help to relieve part of what we call sleep debt, however, it will not make up for any lack of sleep. Also, if you sleep later on your weekends you risk affecting your sleep-wake cycle, making it harder to get to sleep on time when Sunday night comes along.


We’ve learned that we all have a deeply ingrained clock that our body follows, which matches with day and night time. It can difficult to change that habit in a situation like working at night. While the average amount of sleep an adult should get per night falls between 7 to 9 hours, a lot depends on your age, health, and lifestyle. From infancy to becoming a senior, our sleep needs differ greatly. A constant lack of sleep can have long-term adverse effects on one’s health. This is why it’s important to listen to what your body is telling you when it comes to getting too little or too much sleep and making the needed adjustments to ensure better sleep quality.

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