The importance of sleep for a happy and healthy life cannot be understated.
You probably know what it feels like to wake up tired and face the day in a sleep-deprived zombie-like state.
It’s tough… really tough.
Yet, the world is a busy place and it seems like the only way to get ahead – or break even at times – is to give up essential hours of sleep to get more done.
Unfortunately, the human body requires regular, quality sleep to maintain itself.
A person who suffers from long-term, chronic sleep loss may experience additional mental and physical health problems.
It will reach into and negatively impact every facet of a person’s life.
But how much sleep do you really need?
Let’s find out…
The Four Stages Of Sleep
Scientists categorize sleep into four stages that are measured and differentiated with the use of an electroencephalogram (EEG).
They have measured the brainwave amplitudes and frequencies of sleeping participants, and paired these with other biological markers to help determine when the mind is actively shifting through the stages of sleep.
Here’s what they found.
Stage 1 – Non-REM Light Sleep
Stage 1 is the lightest stage of sleep.
The person can be awakened easily and drift in and out of sleep.
The eyes tend to move slowly and muscle activity slows too.
It’s in this stage that people often experience unexpected muscle contractions and the sense of falling that may jolt them awake.
Stage 2 – Non-REM Light Sleep
As the person transitions to Stage 2, their eye movement will stop while brainwaves become much slower.
The brain will intermittently produce a burst of activity in the form of rapid brain waves.
The person’s body temperature drops and their heart rate slows down as their body prepares itself to enter deep sleep.
Stage 3 – Non-REM Deep Sleep
Stage 3 is the first stage of ‘Slow Wave Sleep’ (SWS), or delta sleep.
Delta sleep derives its name from the high amplitude signals with slow frequency known as delta waves.
These cycles provide the most restful sleep of all the stages.
Shallow sleepers who do not reach these stages may sleep an entire night yet not feel rested or alert when they awake. They may also have a harder time getting started once they start to wake up.
A person in this stage of sleep is going to be more difficult to rouse and may sleep through jarring or loud noise and even some movement.
A person awoken from Stage 3 sleep will typically experience cognitive difficulties and have a harder time shifting to the state of being awake.
It is also the stage of sleep where a person is most likely to experience things like bedwetting, night terrors, sleepwalking, or sleep talking.
These behaviors are called parasomnias. They usually happen during the period where the brain is shifting from non-REM to REM sleep.
Scientists previously believed this was a period of quiet and stillness in a sleeping person, but this turned out to be untrue.
The brain is actually quite active as it goes about maintaining and preparing the body for the coming day.
Scientists conducting sleep studies determined that stage 3 delta sleep is actually a necessity. They reached this conclusion after observing that the brain will try to get back into slow wave sleep if it is interrupted during this stage (though it won’t always be successful).
The final stage is REM (Rapid Eye Movement) sleep. It’s the stage in which a person dreams.
Every person does dream, though they may not remember or have an extremely difficult time recalling them.
It’s much easier for people who awake during REM sleep to remember their dreams.
It differs physiologically from other stages of sleep in that muscles are without movement, breathing is irregular, but the EEG shows patterns as though the person is awake.
A person’s heart rate and blood pressure will typically increase as they enter and proceed through REM sleep.
Scientists speculate that muscle paralysis during REM sleep may be the result of an evolutionary advantage meant to keep people from hurting themselves from involuntary activity as they slept.
The eyes do remain closed, but they move from side to side as the sleeper experiences intense brain activity and dreaming that only occurs during this stage.
The person’s breathing may become shallow, rapid, and irregular.
More essential sleep information (article continues below):
- 14 Things To Do Before Bed That Will Put You Into A Deep, Restful Sleep
- How To Fall Asleep Fast: 8 Ways To Drift Off In Record Time
- How Sleep Affects Mood (And Vice Versa) And What You Can Do About It
- 20 Of The Best Songs To Fall Asleep To: A Bedtime Playlist
The Procession Of A Sleep Cycle
A sleep cycle is the period of time it takes for a person to transition through the various stages of sleep, but the person doesn’t just transition from Stage 1 through REM.
Instead, the average sleep cycle looks more like this: Stage 1 (light) – Stage 2 (light) – Stage 3 (deep) – Stage 2 (light) – Stage 1 (light) – REM.
The sleeper returns to Stage 1 after REM and the cycle begins again.
As the night goes on, the person will spend more time in REM sleep and less time in Stage 3.
The first sleep cycle will average about 70 to 100 minutes. The following cycles will increase in length, averaging 90 to 120 minutes per cycle.
The average sleeper will experience three to five sleep cycles throughout the night.
The first REM cycle may be as short as ten minutes, while each subsequent cycle extends to about an hour.
How Much Deep And REM Sleep Do You Actually Need At Night?
The amount of deep and REM sleep an average adult needs will be about 20-25% of their total sleep, depending on how many hours they actually sleep.
At 7 hours, that would be approximately 84 to 105 minutes. At 9 hours, that would be approximately 108 to 135 minutes.
People tend to require less sleep as they get older, which will cause that average to shift.
The average adult needs 7-9 hours of sleep at night. Once a person dips below 7 hours of sleep at night, they start to experience negative effects of their physical health and mental acuity.
How Do I Know If I’m Getting Enough Sleep?
The average person should be able to function without the need for sleep in the course of their day.
Intense drowsiness while working or driving, needing an afternoon nap, feeling sluggish throughout the day, or drifting off while performing another activity are all good indicators that you may not be getting enough sleep.
People who have a hard time waking up and getting out of bed in the morning or who fall asleep within a few minutes of getting in bed may also be sleep deprived.
The negative effects of sleep deprivation are many….
Sleep deprivation increases moodiness, the chance of depression, fatigue, lethargy, impairs the immune system, and impairs learning and cognitive mental abilities.
It increases difficulty in dealing with stress and managing emotions, weakens the immune system, facilitates more physical illnesses, weight gain, hallucinations and delirium.
It also increases the risk of several physical illnesses including some cancers, diabetes, high blood pressure, and strokes.
A person whose sleep is interrupted will not be reaching the deepest, most restorative parts of the sleep cycle.
Any time the person wakes up fully, their brain needs to start the whole cycle over. Broken sleep is just as bad – and sometimes worse – than not sleeping at all.
It can be broken up by outside noises, leaving a television or music on, an uncomfortable temperature, pets, waking children, or mental health issues that prevent the person from reaching those deep, restorative stages of sleep.
Does It Matter When I Sleep?
So far we’ve discussed how Stage 3 non-REM deep sleep is the most restorative and that as the night wears on, this part of the sleep cycle shortens in favor of REM sleep.
This might, then, account for the age-old wisdom that every hour of sleep before midnight is worth two after midnight.
While not strictly true (the 2:1 ratio is plucked from thin air), an earlier bedtime might be beneficial in feeling refreshed come the morning.
In a Time Magazine article, Dr. Matt Walker, head of the Sleep and Neuroimaging Lab at the University of California, Berkeley, suggests that going to bed at some point between 8pm and midnight should give the brain and body all the Stage 3 sleep it needs.
This is because, as the article states, “The shift from non-REM to REM sleep happens at certain times of the night regardless of when you go to bed.”
But there is some inevitable variability as to when people begin to feel tired. Some people really are morning larks, while others are night owls, and they will probably experience that sleepy feeling at different times.
And an individual’s bedtime will change as they get older. Young children need a bedtime that is much earlier than adults, but once they reach college age, they will likely find that they don’t feel tired until closer to the midnight hour.
Beyond this age, a person’s natural bedtime will gradually become earlier once again.
So, yes, it does matter when you sleep. Ideally, you will trust the signals that your body gives you and find the right time somewhere between 8pm and midnight.
Sleep is an essential part of maintaining one’s physical and mental health.
Make it a priority.
It is definitely worth your while to consult with a doctor if you have a hard time sleeping at night.