Rejuvenating sleep – The ultimative scientific primer towards slumber

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“It is a common experience that a problem difficult at night is resolved in the morning after the committee of sleep has worked on it.”

– John Steinbeck


  1. ) Introduction
  2. ) The necessity of sleep
  3. ) Differences In sleep across our limited Dasein
  4. ) Implications of a sleep deprived brain
  5. ) Shorter sleep equals shorter life
  6. ) Sleep disorders
  7. ) Sleep interferences and interventions
  8. ) Conclusion/Related reading
  9. ) References

1) Introduction

This extensive article will bring you closer towards understanding one of natures’ most heralded inventions – namely sleep. You will learn why this third of our lifespan is crucial to our survival and is not only paramount towards consolidating new memories, but also makes – or breaks – our general longevity.

You will be given an in-depth overview about pivotal matters such as the stages of our sleep, biological rhythms, memory and sleep, sleep and its relation to weight, as well as evolutionary and biological principles, which concern slumber.

Furthermore, you will learn, how caffeine, alcohol and prescribed pharmaceutical interventions interfere with this primordial need.

Finally, you will also be shown, why a lack of sleep significantly heightens our innate propensity towards medical conditions, such as Alzheimer’s, cancer, brain damage, cardiovascular diseases, depression, anxiety, diabetes, fertility problems, and so forth.

I highly recommend you take your time to properly digest the hereby disclosed pieces of information, so as to act accordingly and raise your overall well-being.

For the amount and quality of your sleep ultimately determine not only your lifespan, but also your everyday conduct.

2) The necessity of sleep

Sleep – a state of being, which, on average, encompasses about a third of our lifetime. This mostly motionless time of our day refreshes not only our body, but also our mind.

Despite the overwhelming empirical evidence (more than 17.500 studies) regarding the need for a proper amount of sleep, said part of our life still remains a triviality for most individuals, as apparently dictated by our achievement-driven society.

Claims such as “you can sleep, when you are dead”, or “I am able to do just fine with less than 7 hours of sleep”, and so on, are ludicrous at best, yet outrightly dangerous – and quite frankly, blatantly stupid – at worst.

Neglect this vital part of our life and you will pay dearly for it. Whilst the immediate consequences may range from mental fogginess to lacklustre physical abilities, the long-term ramifications are much more severe – and may not only pose a threat to yourself, but also influence others in negative ways, as you will get to know further down this letter-paved road.


The silent epidemic

Don’t you think that it’s quite ironic that a jump from about 39000 meters, with speeds surpassing even the sonic-wall, is able to make its way into the Guinness world record books, yet records, which are related to a lack of sleep are strictly prohibited?

Instances, such as this one, just show, how curbing down our night’s shut-eye is considered exceedingly hazardous. A lack in terms of this innate continuum of our life, on a global scale, has even prompted the “W.H.O” (world health organization), to declare a sleep epidemic.

Scientists have even gone so far as to call our most effective way to reset our brain, as well as our body, the fourth main biological drive in the animal kingdom (apart from eating, drinking and reproducing).

Slumber underpins pretty much everything – so without further ado, let’s get right into the gist of it.


Principles of sleep

The regulation of our bedtime is highly dependent on two factors – one of them being our internal biological clock.


Circadian rhythm
An hourglass next to a normal clock.

Every human being possesses an incredibly finely-tuned internal clock.

An internal twenty-four-hour clock, which not only reigns supreme over your sleep cycle, but also controls other rhythmic patterns, such as timed preferences for eating, drinking, your moods, emotions, the amount of urine you produce, your metabolic rate, your core body temperature and the release of numerous hormones as well.

Every animal, whose live-span lasts longer than a few days, possesses a circadian rhythm.

Weeks of eternal darkness

In 1938, two brave scientists from the university of Chicago have decided to be their own experimental guinea pigs and spent six weeks in Mammoth Cave in Kentucky – one of the deepest caves of our earth. The furthest reaches of this natural architecture are completely engulfed in darkness.

These two men brought loads of water, food, as well as a pair of dismantled high-standing hospital beds with them. Apart from that, said scientist have also decided to track their well-being by means of medical devices.

In total they spent thirty-two days in complete darkness, and have stumbled upon two interesting key findings:


I) Humans produce their own endogenous cycle – this basically implies that sunlight exposure is not necessary for us to regulate our circadian rhythm. These bravehearts did not suddenly fall into sleep, but instead expressed predictable patterns of wakefulness (usually in the realm of 15 hours) and sleep (about 9 hours).

II) The second find showed that the day, as predicated by our internal circadian rhythms, does not last exactly twenty-four hours, but rather twenty-four hours and fifteen minutes, in a consistent manner.


This also explains the nomenclature of the circadian rhythm. Circa means “around”, whilst diam is derived from “day”.



Sunlight, apart from the (and in conjunction with) circadian rhythm, basically poses as a means of resetting our internal clock to about twenty-four hours. Said internal reset also occurs, whenever we eat food, exercise and even socialize. Any stimuli, which prompts our brain to reset our biological clock is termed “zeitgeber” (derived from German – this means “time giver”).

This is also the reason, why individuals who suffer from certain types of blindness do not completely lose their way in regard to the perception of time brought about by external influences, such as the light omitted from the sun.


Sunlight shining through a damaged, brown leaf.

How does light affect dormancy?

Light processing

The uptake of light and its subsequent processing takes place in a specific area of our brain – namely the “suprachiasmatic nucleus”. This tiny structure, which is composed of about 20.000 neurons, basically receives its signal from light, which wanders along the optical nerves behind our eyes to the areas for visual processing at the back of our brain. [1]

This reliable visual information is imperative, when it comes to dealing with our inaccurate timing and helps thusly in correcting this previously explained internal mismatch in the realms of our sleep-wake cycle.


Further regulation

Our circadian rhythm also aids our body in regulating other internal states, such as the core body temperature. Its influences can be seen in the figure below:

A graph of the fluctuation of our body temperature throughout the day.

Our circadian rhythm is not only responsible for generating slumber.


Different biological rhythms

Not everybody displays the same level of wakefulness, respectively sleepiness, at a given time during the day. Generally speaking, humans either fall into one of the two following groups:


I) Morning larks

  • Make up about 40% of our population
  • Prefer to wake up at dawn
  • Function optimally at this time of day


II) Night owls

  • Make up about 30% of the population
  • Prefer going to bed late
  • Remain in a state akin to sleep in the early hours of the day (their prefrontal cortex does not function properly during this “phase”)


The remaining 30% of human beings fall somewhere in between those two distinct groups, but express a slight nudge towards eveningness.

Your genetics are paramount in terms of determining your chronological state of being, which basically implies that altering your sleep schedule constitutes a biological non-sequitur.


Evolutionary reasons

Mother Nature has endowed the human race with the abovementioned differentiating dormancy patterns as a means of decreasing vulnerability. If every individual within a tribe were to get their night’s shut eye at the same time, the respective population would be at risk of decimation for eight hours at any given day.

The night owls would be going to sleep at around one or two a.m. and wake up at approximately nine or ten a.m., whilst the morning larks would already start catching their slumber at 9 p.m. and accordingly wake up at around 5 a.m.

This divergence basically upped our survival fitness by a whopping 50% (only 4 hours of “total vulnerability”).



The bi-directional communication of our suprachiasmatic nucleus and other parts of our brain takes place on a hormonal level. Melatonin, which is released into the bloodstream from the pineal gland, signals our brain and body that the nightly curtain has been drawn.

A great many homo sapiens hold the erroneous belief that melatonin generates sleep. It is important to understand that melatonin simply ushers the commencement of bedtime, but is not responsible for the generation of those rejuvenating hours itself. [2]


Think of it in this way: You partake in a 60-meter dash. The announcer pulls the trigger of the gun (the timing = melatonin), and you start moving towards the finishing line (the race = sleep).


Sleep basically leads to the decrease of melatonin-levels across night into the morning hours. When you get exposed to sunlight, those bright beams hit your optical nerves (through your closed lids).

This results in an application of a mechanism, which is akin to a brake pedal, on your pineal gland that stops melatonin from being further released into your bloodstream.


This figure demonstrates the typical profile of melatonin-release over a timeframe of twenty-four hours.

A depictation of your melatonin release throughout the day.

Exposure to light regulates your melatonin levels.

Jet Lag

Many of us, who tend to travel on a regular basis have experienced a sort of mental fogginess, when traversing different time zones. [3]


Imagine taking a flight to Austria (with your starting point being New York).

Austria is six hours ahead of New York. Let’s say, you depart from New York at 2 a.m. – arriving in Austria at about 5 a.m., which basically means that you’ve skipped a few hours in order to make said transition by air. This biological state of time lag confuses your body insofar as that you – biologically speaking – are led to believe it to be day, whilst it may actually be night.


The turbine of a jet on an airport.

Frequently switching from timezone to timezone leaves its marks on your body.

Your suprachiasmatic nucleus can only make up one hour of “lost” time each day. This means that it will take you about 3 days, to get acclimated to the new time zone.


If you are in the (un)fortunate position of constantly foregoing many time zones due to your line of work, the internal consequences will be much more severe than a few days of lacklustre sleep.


Scientists have studied airplane crews, who tend to frequent many time zones and have come to two rather troublesome conclusions:


I) The first one was that the brain areas responsible for memory and learning have physically shrunk, which suggests a destruction of brain cells due to the biological stress linked to the abovementioned “loss” of time.

II) The second finding showed that the short-term memory of said individuals was significantly impaired, in contrast to peers of the same age, respectively demographic.


The outlook in similar studies, which were conducted within groups that are exposed to time-zone-travel on a regular basis, have proven to be even more alarming. Shift crew members, respectively cabin crew members, have proven to be way more susceptible towards severe medical conditions, such as cancer and type 2 diabetes, than your average joe, or carefully selected individuals, who do not travel as much.


Sleep pressure

The second sleep-determining factor (the first being the circadian rhythm, as you may recall) is being governed by another hormone – namely adenosine.

Adenosine is a substance, which rises in a linear fashion by the minute. The longer you are awake, the more adenosine will have accumulated in your brain. This biological structure is tantamount to a barometer. It continuously registers the elapsed time, since you have awoken from your slumber.

The higher your adenosine, the greater your internal pressure to sleep – you will consequently be sleepier, as time goes on. At its peak, an irresistible urge to indulge in renewing slumber will overcome you – given your circadian rhythm is not messed up due to negative influences, such as jet lag. Most people will experience this kind of overwhelming pressure after about twelve to sixteen hours of wakefulness.

A depictation of your sleep wake cycle. Your circadian rhythm is the sinus wave and your adenosine is a pretty linear rise and fall throughout the day.

An interesting interplay between sleep pressure and the circadian rhythm determines our propensity towards slumber.

Your circadian rhythm constitutes the dotted sinus curve in this figure, whilst adenosine poses as the wave-like line.

During times of the day, where the discrepancy between the two parts of the graph is at its highest, your propensity towards sleep will be heightened as well.


The state of sleep

Sleep is marked by two somewhat universal tell-tale signs.


I) One constitutes the loss of external awareness. Your gate of external perception – namely the hypothalamus – simply blocks all external stimuli, even though you still “perceive” them. Roughly speaking, they are not being redirected towards your cortex, where they would be consciously perceived.

II) The second one expresses itself by means of a distorted sense of time. After you have slept for a few hours, you tend to check the time, for you have been unaware of the time that has passed, since you have decided to go to rest.


At a non-conscious level, however, this time tracking occurs at an incredibly precise rate. You may have probably already experienced this internal precision first-hand.

You have decided to get up the next day at 8 a.m. – you set up the alarm clock and went to bed. Your sub-conscious has logged the time and woke you up even a few minutes before you have set up the alarm clock. Scenarios such as this one are only possible due to your subliminal chronological finesse.


Getting into the nit-grit of sleep

There are two distinct types of sleep, which are common across not only homo sapiens, but a broad array of other animals as well – namely NREM-sleep and REM-sleep.


Phases of sleep

NREM (“Non-rapid eye movement”-sleep) consists of 4 stages – increasing in depth. Depth as in a steadily growing difficulty in terms of waking somebody up.

The longer you sleep, the more REM sleep you’ll be able to catch.

All ninety minutes our brain switches from NREM-sleep to REM-sleep. “Rapid eye movement”-sleep lasts considerably shorter than its counterpart. Yet the ratio between NREM-sleep and REM-sleep shifts from cycle to cycle.

REM-sleep increases, as the night goes on, whilst NREM-sleep decreases. NREM dominates our early sleeping hours and REM dominates the latter half of our slumber. Both phases are crucial when it comes to not only strengthening our cognitive abilities, but also recovering from the strenuous day in a general manner, as we will discover later on.

Most humans tend to cut off their bedtime at one end or the other, which is something that should not be taken lightly. Let’s say you are getting to sleep at 12 p.m., whilst rising at 6 a.m., since you have to take the early train, in order to make it to your job.

On the surface, you are robbing yourself of 25% of the recommended daily dose of sleep, but looking beyond that the shortage appears to be much more severe.

Speaking from the standpoint of REM-sleep, you are actually foregoing 60-90% of said sleep phase of all your REM-sleep, even though you are only losing about 25% of your overall sleep.

This works both ways. If you wake up at 8 a.m., but decide to go to bed at 2 a.m., you are actually robbing yourself of a significant amount of NREM-sleep.

As with sleep, there is no such thing as getting away with cutting it short at one end and getting away with it.


The formation of sleep

Our brain generates sleep by means of brainwaves. Brainwave activity, in this context, can generally be broken down into three different states.

A depictation of our brainwave states.

Fascinatingly, the brain waves during REM sleep and wakefulness are pretty similar.


I) Wakefulness

Whilst being awake, your brainwave activity is somewhat frenetic. This “fast frequency” brainwave activity is called like that, for your brainwaves move up and down at a rate of approximately 30 – 40 times per second.

This electric drumbeat expresses itself in a highly erratic manner. The reason being that different parts of your brain have to process distinct pieces of information

Wakefulness is predominately concerned with reception. Its primary function lies therefore in the uptake of external stimuli.


II) (Deep) NREM sleep

These types of waves are quite slow in comparison to the abovementioned chaotic rhythm. They typically range from 2 – 4 waves per second. These decelerated curves are even somewhat predictable (although only in the range of a few bars).

The downbeat of the slow-waves cycle is, from time to time, being overshadowed by a peculiar layer, which only lasts for a few seconds. Those distinct sheets of overarching brainwave activity are generally being referred to as “sleep spindles”.

These spindles occur during both the lighter and the deeper phase of NREM sleep. Their primary function is that of a nocturnal soldier, who shields you from external noises and thus protects your brain from interference, whilst sleeping.


By the way, most deep-sleep brainwaves originate in your frontal lobes. A place, which is located at about 5 cm’s above the bridge of your nose, right between your eyes.

Deep NREM sleep is a state of neural collaboration – thousands upon thousands of neurons fire together, which also explains your loss of external consciousness.

The severance of perceptual bonds with the outside world, which occurs as a result of an internal barricade in terms of relaying sensory pieces of information from the thalamus to the cortex, as you might recall, leads to the already mentioned slow-wave activity in our brain.

During NREM sleep we are neither in a state of perceiving time, nor are we dreaming. This phase of sleep aids our cortex insofar as that said part of our brain calms down and soothes into its default mode of activity, which is commonly known as deep slow-wave sleep.

NREM sleep is predominately concerned with inward reflection. It acts as a fertilizer in terms of transferring pieces of information and distilling memories.


III) REM sleep

This type of sleep is often referred to as “paradoxical sleep”. Speaking from the standpoint of brainwave activity, said state is barely distinguishable from its wakeful counterpart.

MRI scans have shown that there are even certain areas of our brain, which are up to 30% more active during this state than during wakefulness.

During this phase, the gate of the thalamus opens up once again, albeit with a slight twist. This time our perceptual redirector allows signals of emotions, motivations, and memories (of the past and the present) to make their way to their respective designated areas of our visual, auditory, kinesthetic and sensory cortices of our brain.

This phase of our sleep is also responsible for creating the oftentimes bizarre and downright absurd stories, known as dreams.

REM sleep is predominantly concerned with integration. It allows us to interconnect barebone ingredients, and perceptions, so as to build a constantly more precise model of our world, which includes innovative insights and problem-solving abilities.

During REM-sleep, you will create more links between distant, often times unrelated pieces of information.

REM sleep constitutes a highly creative process. We tend to draw parallels between topics, which are more often than not miles apart – speaking from the standpoint of a distinct set of areas, that is (i.e. politics – nature, and so on).



During sleep, all of our muscles, which are related to controlling automatic operations, such as breathing, and keeping us alive, roughly speaking, are still working, yet involuntary muscles are basically shut down.

This “feature” is commonly referred to as “atonia”. A powerful signal, which travels all the way down from your brain stem to your spinal chord, instigates your postural muscles, such as your biceps and your quadriceps to lose all their strength and tension.

The evolutionary explanation is linked to experiencing dreams. Said fabrications of our mind are tightly intertwined with motoric commands.

“The brain paralyzes the body, so that the mind can dream safely.”

If you were to act out your wildest fantasies, it would not take you too long, before you would put yourself in harms way and probably be awarded the Darwin award. Just imagine sprinting away from your imaginary foe, whilst being completely oblivious to your imminent surroundings!


Two ducklings sitting in a basket.

All species experience sleep, or a state akin to that.

Sleep across all species

Sleep – or a state akin to that – is a need of all animals, which have been studied up to date. It is thought that the active and passive phases of bacteria pose as the evolutionary precursor to our slumber.

Even the simplest life forms acted out some sort of sleep as a response to the day-night-cycle of our planet.


Divergent states of sleep

There are four encompassing distinctions between sleep within the span of natures’ creations.


I) Sleep duration

One such differentiation can be found by paying heed to father time. Certain animals, such as the elephant, require just four hours of dormancy each day, whereas species, such as the brown bat take up to nineteen hours each day, so as to get a good night’s shut eye.

Inspecting the phylogenetic tree as means of coming to terms with differing durations of slumber is actually irrelevant, since sleep needs, within the same evolutionary branch, can differ highly from each other.

Take the family group of rodents as an example. Squirrels take about 15.9 hours each day for this basic necessity, whereas degu only need about 7.7 hours. On the other hand, there are animals, which couldn’t be more dissimilar (not only speaking from a strictly phylogenic standpoint, that is).

Guinea pigs and baboons need the exact same amount of sleep each day – 9.4 hours.

Scientists are not entirely sure, what’s responsible for these drastic differences, yet the size of the respective nervous system, its complexity, as well as its body mass are meaningful predictors. At least to a certain degree.

Other reasons are dietary types (carnivore, herbivore, omnivore), predator/prey balance within a habitat, the presence and nature of a social network, as well as the metabolic rate.


II) Sleep composition

Every observed species’ sleep has one phase in common: that of NREM. Only birds and mammals, which made their appearance later on, in the evolutionary timeline show full-blown REM sleep.

Aquatic mammals, such as the dolphin, however, are somewhat of an exception. Although a report in 1969 states that a pilot whale underwent REM sleep for six minutes, most modern day assessments have shown us a different type of picture.

This shortage, or total absence of REM sleep in mammals, who roam the everchanging depths of fluid molecules, does make sense, since this type of sleep prompts the relaxation, as well as the loss of functionality in our muscles. If these mammals would indulge in this type of slumber, they would most likely drown.

Curiously mammals, which are partially aquatic, such as pinnipeds (derived from Latin “pinna” – fin | “pedis” foot), split their time between land and sea. Take fur seals as an example. These coated paddlers only indulge in NREM as well as REM sleep, when they spend their time on land. Whilst drifting through the waters, those mammals have shown no observable amount of REM sleep. They instead feast on a snooze diet full of NREM sleep.

Another interesting evolutionary find, within this given context, is that of the distinction between birds and mammals. Those two groups have evolved separately, yet both possess REM sleep, which means that said stage of our slumber may henceforth have been birthed twice.

Speaking from a Darwinian perspective, whenever a feature propagates itself across (unrelated) lineages, not only vertically, but also horizontally, you can be sure that it is of utmost importance and often indicates a fundamental need.


A short excursus on sleep deprivation

Experiments, which were geared towards creating a hunger for sleep, as a result of pulling all-nighters, have led us to two interesting finds.

a) Unsurprisingly, the night after a mammal (humans included), has been deprived of sleep, they take longer to recover. Humans take about 10-12 hours of slumber, so as to “make up” for their lost Z’s. The technical terms for this is “sleep rebound”.

b) NREM sleep rebounds harder

In the first night after sleep deprivation, our brain will be prompted to consume much more NREM sleep. This lopsided hunger, however, does not imply that NREM sleep is more important. A tidal shift happens in the following nights – our brain gathers much more REM sleep.

Make no mistake, our brain desperately tries to regain both types of sleep, but it does not even come close to “catching up” the sleep that has been lost. This holds not only true for both phases of our sleep, but also for the total time of sleep.


III) Our way of sleeping

Cetaceans, such as dolphins and whales, are able to sleep in a unihemispheric manner. This means that, during sleep, one half of their brain is still active. After one side has done its recovering deed, the brain switches and now the other half of the brain gets to relax.

Recent studies suggest that humans are capable of indulging in a mild form of unihemispheric sleep. Whilst our dormancy in familiar environments shows no sign of “abnormality” in regard to this specific matter, catching our Z’s in unfamiliar environments actually causes some parts of our brain to stand on guard. The reason being that, whilst we have been awake, our brain has registered the environment as potentially dangerous. Subsequent nights in said potentially harmful context have shown that this process of acclimation instigates our brain to lower its guard.

This is perhaps the reason, why so many of us find themselves in dire straights, when it comes to getting the much needed slumber during our first night in a hotel.


IV) Different sleep patterns

The animal kingdom never ceases to amaze. Birds during transoceanic migration have shown to take “ultra-naps” – brief periods of sleep, which on average last only a few seconds.

These quick phases of recovery are born out of necessity, since said airborne mammals literally fly thousands of kilometers during their strenuous endeavor.


Homo sapiens’ preferred sleep pattern

Most westerners have settled on sleeping in a monophasic way. This means that we get the totality of our sleep in one fell swoop – during the night. Most individuals get less than seven hours of quality rest.

Looking at hunter-gatherer tribes, such as the San people in the Kalahari Desert, which conduct themselves without any electricity, a clear distinction becomes apparent.

These folks still sleep as nature dictates – in a biphasic way. Whilst getting the majority of their dormancy during the night, those individuals also include a short mid-afternoon nap (typically in the range of 30 to 60 minutes) in their daily “schedule”.

All humans, irregardless of their geographical location, respectively their socioeconomic status, have an ingrained sleep pattern. This hardwired part of our DNA is the reason, why we favour an afternoon nap – the post-prandial alertness dip (prandium stands for “meal”). Our innate tendency towards low-level alertness should not be discarded.

A study of 23.000 healthy greek adults has turned out to be another humbling Greek tragedy. These individuals have been tracked over a span of six years. As the majority of them had to abandon their siestas, their cardiovascular health has taken a hefty toll.

Individuals, who discarded their practice of daily siestas went on to suffer a 37 percent higher risk of death from disease related to the heart, compared to those, who continued their daily ritual of napping.

The effects of this sleep-related shift in the mentality of those Europeans have proven to be especially devastating in workingmen, where the mortality risk rose by well over 60 percent.

It turns out that the secret to a long life is a healthy diet and a biphasic sleep pattern, after all.

3) Differences In sleep across our limited Dasein

One has to wonder, whether there are actually any constants in our existence. One thing is clear: sleep is definitely not one of them.


Baby sleeping amidst a cozy blanket.

Babies spend most of their time blissfully sleeping.

Babies will spend most of their time in a state of dormancy. Whilst many parents tend to believe that their offspring is awake, whenever, in utero, some sort of kicking can be recognized, it is most likely the case that the little bugger experiences REM sleep.

As you know by now, REM sleep is the phase, where we dream and enact – at least mentally – a sort of wandering process throughout the wondrous constructs of our mind. Whilst the brain of an adult has no problem, when it comes to inhibiting their responses on a muscular level, the same does not go for our progeny.

Babies at the early stages spend most of their time being in a mixture of REM sleep (6 hrs/day), NREM sleep (6 hrs/day) and an intermediary phase of sleep, which can not be properly categorized (12 hrs/day).

It is only at the onset of the third trimester that our new blood starts to experience a state akin to wakefulness. This state does however not last that long either – only two to three hours each day.

The detailed creation of our brain happens during the second and third trimester. These interludes are also times, where the amount of REM-sleep rises to unforeseen heights.

Rapid-eye-movement sleep principally acts as a sort of electrical fertilizer – stimulating the growth of neural pathways during this highly critical time of our organisms’ existence.

This synaptogenesis poses the first critical period of plasticity, as described in my article on neuroplasticity.

There are devastating consequences, If you disturb or impair the REM sleep of a developing infant brain – irrespective of it being in the pre- or early-post term phase.

Studies in a variety of mammalian species have shown that robbing the brain of said phase results in a forever underconstructed cerebral cortex. The blockage of REM sleep has ground the construction of the neuronal rooftop to a halt. Day after day of diminished REM sleep, the sparsely fabricated cerebral rooftop showed no signs of growing any further.

After those mammals have finally been granted a full scoop of proper sleep, the rooftop assembly restarted, yet it did not accelerate, nor did it ever get completely back on the right track.


Autism and sleep

There exists a clear correlation between a lack of sleep during our pivotal years and autism spectrum disorder (ASD). [4] This abnormal state of mind has been linked to a distorted synaptogenesis. Inappropriate synaptical wiring – more precisely in the realm of numbers, formation respectively, appears to be central to this condition.

The circadian rhythm of those sufferers is also weaker than in their healthy counterparts. Besides, the overall amount of generated sleep is less than that of normal individuals.


Hermit the frog lying on a bench, being obviously intoxicated.

Alcohol causes immense damage to the vital periods of sleep of our offspring.

Alcohol on the infant brain

Alcohol is one of the mightiest suppressors of REM sleep. The brain of infants, whose mothers do not disdain from gulping down these types of poisonous beverages, have shown a 200% reduction in terms of vibrant electrical activity during this specific phase of slumber. [5]

Studies have also linked a higher likelihood of developing neuropsychiatric illnesses in the child to alcohol use during pregnancy. [6]

As if this wasn’t enough, those drinks have also proven to lower the overall rate of breathing during REM sleep. The normal breath rate of 381 per hour during natural circumstances has plummeted to a measly 4 per hour in fetuses that were trenched in alcohol. [7]

This holds true, even if you, as a mother, do not consider yourself to be a heavy drinker. Just one or two glasses of wine affect your unborn child in unhealthy ways.

Those beverages are still not to be trifled with, even if your child has already been born. If you ingest alcohol, this substance will be absorbed by your milk. Breastfeeding will therefore lead your infant child towards taking up this fluid as well.

Babies, who consume alcohol-laced milk will experience a fragmented sleep. They are longer awake and have to endure a 20 – 30 % suppression of REM sleep shortly afterwards. Following this disturbance, the fetus or newborn tries desperately to regain every hour of this lost obligatory sleeping stage. [8]

The long-term implications related to the practice of those unhealthy habits are currently not fully understood, but one thing is clear: Blocking or reducing REM sleep in newborn animals not only hinders the development of their most versatile organ, it also distorts its development. Adults, who have been exposed to said practices are as a result socially abnormal.


Young Kids

Infants, as well as young kids, show a different sleeping pattern: polyphasic sleep. The younger they are, the more often they tend to wake up during

Two young kids walking on top of a wooden bridge.

Young kids experience a rather fragmented type of slumber.

the night. The reason for those, often vocal, intersections of awakening, is a lack of development of the suprachiasmatic nucleus – the area that governs our circadian rhythm.


Newborns show small signs of a daily rhythm by the age of approximately three or four months. After one year this internal clock has most likely been fine-tuned.

At the age of four the circadian rhythm reigns supreme, when it comes to governing the child’s sleep behaviour. Our progeny now shows a somewhat maximized proclivity towards sleeping through the night, whilst occasionally catching a few Z’s in the form of a single nap.

By the way, a four month-old infant spends about 50% of their fourteen-hour long sleep in the REM phase, and 50% in the NREM phase.

As the respective homo sapiens grows, its propensity towards NREM sleep rises. A five year-old will spend about 70% of their eleven hours of total daily sleep in the state of NREM, and only 30% in the REM phase.

This balance will plateau at an 80/20 split (NREM/REM) by the late teen years. This will be the case for early, as well as midadulthood.


Three adolescents sitting at a table and talking, as well as sipping coffee.Adolescents

As we age, there is an overall increase in the department of our sleep-effectiveness. Changes are mostly related to deep NREM sleep. It is thought that deep sleep is a driving factor, in relation to brain maturation, not vice versa.

The dictating forces of deep sleep do not shape our brain in a uniform manner. Apart from the discovery that that the deep-sleep intensity changes with the developmental stages of our cognitive superweapon, the pioneering sleep researcher Irwin Feinberg has observed another highly interesting feature of our being.

The rise-and-fall pattern of maturation always took its turn starting at the back of our brain, which is in charge of visual and spatial perception.

As adolescence advanced, it progressed consistently forward. The tip of the frontal lobe poses as the very last stop of this journey of maturation. This part of our brain allows us to think in a rational way and make critical decisions.

Henceforth, the back of the brain of an adolescent individual was more akin to that of an adult, whereas the front remained in a more child-like state at any given moment during this developmental timeframe. [9]

This also explains, why most teenagers and adolescents are prone to act in riskier and more irrational ways. Their rational-thinking faculties are simply not developed enough. Completing the arduous task of sculpting a fully functional mental muscle does not happen until children reach their mid-twenties.

By the way, the circadian rhythm of adolescents favours, in comparison to that of children, later bedtimes. Teenagers are, speaking from a biological standpoint, at later hours, even more wakeful than adults. Most adults tend to attempt to rest at eleven p.m. – a stark contrast to the peak wakefulness of the majority of adolescents at that time.

This poses a society wide problem, given the early starting hours of most schools – a problem, which has not been addressed as of yet, it seems.

Mother nature has most likely employed this shift of sleepiness, so as to foster independence. One of the most heralded goals of adolescent development appears to be the process of unbuckling oneself from one’s caretakers.

Whilst this socio-evolutionary happening does not result in a full separation between progeny and parents, it still tilts the respective soon-to-be adult towards an independent way of living.


Midlife and old age

A common erroneous belief is that of a reduced need of sleep in seniors. Whilst it is true that the older one gets, the more disordered the sleep turns out

People moving throughout a hall.

As we grow, our sleep starts getting worse and worse.

to be, it is blatantly wrong to assume that older adults need less sleep. These poor souls are simply less capable of generating this free panacea.


As we age, three key factors related to sleep become apparent:


I) Reduced quantity/quality

A general decline of vital deep NREM sleep hits us way earlier than one expects. Our late twenties and early thirties induce a sleep recession. The electrical quality and quantity of said sleep phase diminishes significantly, as we grow older.

Those deep NREM brainwaves recede in their size, their power, as well as their number.

Passing our mid- and late forties, we will have already lost about 60 – 70 % of deep sleep, in comparison to our more youthful days.

By the time we are seventy years old, we will have lost 80 – 90 % of our much needed deep sleep.

We are not able to have a good grasp on the declining electrical quality of this type of deep slumber, which in turn prompts us to look over the deteriorating effects of this natural deficiency and may lead us to attribute health problems to other possible causalities.


II) Reduced sleep efficiency

One perceivable feature of our worsening sleep is that of fragmentation. Older individuals tend to wake up more during the night – a chief factor towards this stressor is, amongst the possibility of experiencing other medical conditions, a weakening bladder.

A reduction in sleep efficiency means that people, who suffer from it, tend to lose overall time asleep. Let’s say you decide to sleep for eight hours. If you were to spend all eight hours slumbering, your sleep efficiency would be at a 100%. Spend only six out of those eight hours sleeping and your efficiency would be at 75%.

Teenagers enjoy a sleep efficiency of around 95%, whereas the efficiency of individuals in their eighties hovers around 70 – 80%. [10|11] Good-quality sleep involves a sleep efficiency of around 90 percent.

Formulating it this way does not sound too bad, but if you do the arithmetic, you would conclude that homo sapiens within this age bracket spend as much as one to one and a half hours being awake.

Studies, which assessed thousands of adults, have concluded, that a lack of sleep efficiency results in a myriad of negative implications. A higher mortality risk, worse physical health, a higher probability of suffering from depression, less energy and lower cognitive function, which typically results in forgetfulness are some of these by-products of a reduced efficiency in the department of slumber.

Disrupted sleep also shows signs of correlation with dementia.


III) A shifted circadian rhythm

An earlier release of melatonin often leads elderly individuals to get to bed earlier and wake up sooner than their younger peers.

This may sound insignificant, but it actually leads to a lot of troublesome consequences, such as falling asleep on the couch, or in other unconventional places. This causes said troubled humans to lose sleep pressure in the form of adenosine.

This, in turn, means that they will have problems falling asleep, when it truly matters. Moreover, our body curbs back the amount of released melatonin, as we age. I am sure that by now you have already figured out, where this leads to: a vicious, self-perpetuating cycle of continuously sub-par sleep.

Unfortunately, the same areas in our brain, which promote deep sleep, atrophy earliest and most severely as we age.

Scientists around the globe have demonstrated over and over again that deep sleep is crucial, when it comes to cementing new memories and retaining new facts.

Poor memory and poor sleep are highly intertwined with each other – it comes henceforth as no surprise that the progressing brain deterioration in older adults explained 60 percent of their inability to produce generated deep sleep.


Somebody holding an old picture in their hand.

Sleep is imperative, when it comes to generating new memories.

The link between sleep and memory

Our hippocampus acts as a short-term reservoir for memories, which are essentially in the realm of facts. Its capacity is limited – just like that of an USB stick. Exceed its limits and you will overwrite data – this neurological process has been coined “interference forgetting”.

People who nap, have a 20 percent advantage, in terms of learning new facts, as opposed to their non napping counterparts. Sleep henceforth restores our ability to “save” new facts. This is related to the lighter stage 2 phase of NREM sleep.

Sleep spindles; those short bursts of electrical impulsivity, as previously discussed, have been proven to be the cause for this memorization process, as induced by sleep. Even more astounding has been the discovery that electrical impulses between the hippocampus and the cortex, which repeat themselves and occur every 100 to 200 milliseconds, are responsible for the transfer of memories. These short-lived impressions are basically getting re-located from the floating state of short-term memory, which reigns supreme in the hippocampus, to a more solid state of existence in the cortex.

Scientists have concluded that the amount of sleep spindles correlates directly with the degree of over-night restoration, as linked to our learning abilities. Unsurprisingly, one’s capacity to generate those bursts of electrical activity diminishes over time. People in their sixties and seventies suffer from a 40 percent deficit regarding the creation of those spindles.

After learning, sleep helps our consolidating of newly acquired pieces of information. Experiments have proven time and time again that sleep offers a memory retention benefit of 20 – 40 %, when compared to being the same amount of time awake. [12]

With that being said, our early-night sleep, which is rich in deep NREM sleep offers superior memory retention savings, in comparison with late-night REM-rich sleep.

Another highly interesting find is related to retrieving our stored pieces of information. Prior to sleep, we use our hippocampus – the short-term solution towards saving data –, to gather collected impressions.

After having slept, we make use of a different storage warehouse, so as to gather the same pieces of information – namely the neocortex. It is located at the top of the brain and serves as a long-term storage for factual bits of cognitive input.

Naps, as short as 20 minutes, have been shown to elicit higher cortical retention, provided that the respective individual had its fair share of NREM sleep.


Sleep and motoric retention

Sleep not only grants us a click on the factual “save” button, but it also allows us to consolidate motoric skills. A good night sleep literally soothes out the rough patches in abilities, such as playing the piano.

Tedious transitions, which have been prior to sleep executed in a rather defective way, have become easier after rest.

Motor memories, as it turns out, are not being transferred to the long-term memory, but rather to brain circuits, which do their deed on a subconscious level.

Stage 2 NREM sleep (and more specifically the last two hours of an eight-hour night of sleep) is responsible for raising the speed and finesse of motoric skills that have been acquired throughout the day. Interestingly, sleep spindles have only increased in areas above the motoric cortex.

The more sleep spindles, the better the performance upon awakening.

4) Implications of a sleep deprived brain

It is no wonder that world record attempts at staying awake longer than naturally intended have been banned. Countless studies have shown the adverse effects of losing out on sleep, yet most individuals are not aware of their impeding negative implications.

We all have been educated on the dangers of drinking whilst being in a state, far from sobriety.

Alcohol surely poses as one of the biggest reasons for car-related accidents around the globe, but there is one other highly dangerous, yet often times neglected cause for those dangerous mishaps: a lack of sleep.

Whereas alcoholics are still somewhat in control of their given situation, a lack of sleep may express itself in a short period of complete unresponsiveness, which is commonly known as “microsleep”.

These bouts only last for a few seconds, and are usually experienced by individuals, who are chronically sleep-deprived (getting less than 7 hours of sleep on a regular basis). The eyelids are either shut completely, or partially, and the respective sufferer becomes blind to all channels of perception. The troublesome component of this continuous sleep deficit can be easily spotted in the realm of decisive motoric action.

Even speeds as low as 40 km/h, with a modest angle of drift, can lead you to switch from one lane to the other, crash into incoming traffic, and henceforth be enough to put a halt to the story of your life for good.

You do not need to be ten seconds asleep to get a feel of where this is going. Two seconds will do just fine – and it may very well be the last microsleep you’ll ever experience.

Another type of drowsy accident may manifest itself, when an individual has not slept for twenty hours. The culprit simply falls asleep at the driving wheel. Those bouts last longer than two seconds of microsleep.


Dangerous shortage of Z’s

You may wonder how long it actually takes, before sleep impairs your overall performance. David Dinges at the University of Pennsylvania has researched this and other related questions, which eventually led him to stumble upon important key findings. Mr. Dinges has conducted experiments, during which individuals have been divided into four groups and tested for about two weeks:


I) 72-hours of total sleep deprivation

II) 4 hours of sleep each night

III) 6 hours of sleep each night

IV) 8 hours of sleep each night


Slowness, missed responses and growing sleep debt

Those participants who have been sleep deprived, not only had a reduction in their overall reaction time, they even showed slight lapses, where they stopped responding altogether. Microsleep, as previously illustrated, has become commonplace amongst those, who had less than 8 hours of sleep each day.

Individuals in the 72-hour bracket had, after the first night of no sleep, already experienced a 400 percent increase in terms of focus-related leaps. This negative correlation rose in severity, as their bodies have become more and more sleep-starved.

Those, who got to sleep for 4 hours each night showed the same reduction after six nights of sub-optimal slumbering time. After eleven days of only of hours of sleep, those same individuals’ performance has been diminished even further. They were now conducting themselves in a state akin to somebody, who pulled two back-to-back all-nighters. Their bodies basically acted, as if they hadn’t slept for 48 hours straight.

The most worrisome aspect, from a societal perspective, is that of those, who have had 6 hours of sleep each night. After just ten days of less time asleep than necessary, their lacklustre performance was tantamount to somebody who hasn’t slept in 24 hours.

Just as in the other groups, the performance-diminishing effects have started to accumulate, as time went by. If this experiment would have continued, these participants’ sleep debt would have accrued.

Unsurprisingly, those who had eight hours of sleep each day, maintained a stable, pretty much perfect performance.


Unawareness of sleep-deprivation

The most mind-boggling found of this study relates to our subjective sense of sleep. Participants, who have been asked to sleep deprived they felt, constantly underestimated the degree of their performance-handicap.

These statements’ validity was tantamount to somebody, who has had one too many drinks, who’d tell you that he’s just fine driving home. A highly risky and harmful subjective misconception.

You should really engrave this part of the article in your brain: You do not consciously know, when you are sleep deprived. This is one of the harshest and most fear-inducing truths of a lack of sleep.

And also one that the majority of humanity is literally unaware of. I am sure, you know a person, who claims that they can get by just fine with less than six hours of sleep, and thus lives in a perpetual state of sub-optimal function.

Now, as you already know, there is no such thing as recovering all the lost hours of sleep. Our brain is simply incapable of doing that. Many chronic sleep deniers believe they can regain their lost sleep during the weekend.

Dinges has found that, even after three nights of recovery sleep, performance still did not reach the heights of the original baseline assessment, which was conducted before the participants’ sleep deprivation.

Generally speaking, the human brain takes a hit after you are being awake for around sixteen hours. You need eight hours of sleep, in order to function optimally – even seven cause you to get cognitively impaired in the long run.


The sleepless forefront

A very rare group of people is able to survive on just six hours of sleep, without showing significant signs of cognitive impairment. As it turns out, those same individuals appear to have a sub-variant of a gene named “BHLHE41” (a.k.a. DEC2).

Some of you might now believe that you fall into this category of specialness. This is extremely unlikely, for but a fraction of 1 percent of the population happens to be truly resilient to the effects of chronic sleep restriction at all stages of brain function. There is a higher chance of you getting struck by lightning (lifetime odds hover around 1 in 12.000), than being truly able to live on insufficient sleep, as a result of a rare gene.


Implications of too little sleep

Higher emotional rashness and sleep deprivation go hand in hand. Those who lack sleep have been shown to express heightened activity in the amygdala. A part of our super processor, which basically regulates our emotions.

An amplification of more than 60% in terms of emotional reactivity was the result of depriving individuals of sleep. Said sufferers’ emotional department has reverted to a primitive state of being, which has shown itself by means of uncontrolled reactivity.

This happens, because the prefrontal cortex, which basically acts as a brake, gets somewhat uncoupled from the amygdala – the gas pedal of emotionality.

It does not matter, whether you have gotten less sleep than necessary across several nights, or just one. The outcome is the same. Your rationality goes to hell in a handbasket.

Just as a side note: different parts of your deep emotional centers, which are seated above and behind the amygdala – called the striatum, which are linked to impulsivity and reward – are basically getting soaked in the neurotransmitter Dopamine. Rewarding, pleasurable experiences cause those regions to become hyperactive, if you are sleep-deprived.

A sad girl sitting on a bank.

Heightened emotionality goes hand in hand with too little sleep.

The reaction is the same as that of the amygdala. The abnormal sensitivity of said hedonic regions is also a result of lost rational influence from the prefrontal cortex. Your underslept brain does therefore not cause you to remain in a state of continual negativity, but rather prompts you to swing between both extremes of the emotional pendulum – positivity, and negativity.

One extreme does not counter the other one. Aggression, bullying, and behavioral problems have been linked to too little sleep, whereas extreme mood-swings in the direction of positivity have also shown to lead individuals to sensation-seeking, risk-taking, and addiction. [13, 14, 15]

Oh, and the neurological pattern of brain activity in people, whose sleep has either been disrupted or blocked, is comparable to that observed in many psychiatric conditions. Are you convinced yet that a lack of sleep not only sucks for you, but also for those around you? No?

Don’t fret, there’s more to come.



Experiments have shown that those, who are sleep-deprived retain 40 percent less than their fully-rested peers. It does not take much, so as to trigger this internal deficit. Disrupt the depth of an individual’s NREM sleep with infrequent sounds, which in turn prevent deep sleep, and the respective person already suffers from the negative consequences.

They do not even need to wake up, in order to experience brain deficits and lessened learning abilities.

Sleep and the correlating consolidation of memory is basically an “all-or-nothing event”. “Catch-up” sleep is pretty much useless as well, for sleep is no bank – there is no such thing, as a debt that can be paid off later on. If you do not get sleep the night after having acquired new bits of input, you will lose most of the newly forged memories.


A link to Alzheimer’s

The brain of somebody with Alzheimer’s shows lots of built-up proteins called “beta amyloid”. These lumps of proteins are poisonous to neurons and kill the surrounding cells of nature’s most heralded construct. During the early onset of this devastating disease, those plaques accumulate in the area that is crucial to generating deep NREM sleep – namely the middle part of the frontal lobe.

Those ravenous heaps are not caused by Alzheimer’s, but they are linked to it. The secret related to this link may lie in the glymphatic system of our brain. The team around Dr. Maiken Nedeergard has made the phenomenal discovery that our brain possesses some sort of sewer system. [16]

During deep NREM sleep, our glia cells shrink up to 60% in size. Glia cells basically support neurons. This, in turn, enlarges the area around the neurons and allows cerebrospinal fluid to flush out unnecessary metabolic refuse, which has accumulated during the day. Other dangerous proteins, such as tau, get swept away during this cleansing process as well.

You can see, where this is going. The less deep sleep you catch, the more beta amyloid builds up, which decreases your ability to catch deep slumber, and thusly leads to the accumulation of more toxic metabolic debris. This vicious cycle significantly raises your propensity towards developing Alzheimer’s and should not be taken lightly!

5) Shorter sleep equals shorter life

Sleep is the foundation upon which our health rests. Studies have shown that there exists a clear link between sleep loss and heart-related diseases. A progressively shorter sleep has, among others, been demonstrated to lead to a 45% increase in developing and/or dying from coronary heart disease, and over a 14-year period lead to a 500% increase in suffering from a cardiac arrest in individuals, who got less than six hours daily.[17]

Furthermore, those who are older than 45 years and get less than six hours of sleep each night, are 200 percent more likely to be on the receiving end of a stroke or heart attack during their time on earth.

Even just one night, during which you get one or two hours less than the recommendation, will cause your heart rate to rise, hour upon hour, and significantly raise the systolic blood pressure within the vasculature. [18]


Sleep and food

Sleep also shapes your feeling of hunger.

The less you sleep, the likelier you are to eat. Sleep also helps our bodies regulate hormones. Two of those are responsible for controlling our appetite.

  • Leptin: It triggers a sense of feeling full. When those circulating levels are high, we simply do not feel like eating.
  • Ghrelin: It prompts us to feel hunger. When those circulating levels are high, we start to feel hungry.

A lack of sleep decreases levels of leptin, whilst simultaneously heightening the levels of ghrelin. This case of hormonal double trouble manifests itself in two negative ways: First off, as your circulating leptin decreases, you start feeling less full. On top of that, as your ghrelin increases, you suddenly get the urge to indulge in food.

Deprive yourself of sleep and you will feel the full blunt force of this two-edged sword. For this dangerous shortage also causes your body to preserve more fat, whilst burning precious muscle mass, as it turns out.


Sleep and diabetes

A shortage of nature’s panacea may express itself in the form of a fearsome malady – Type 2 diabetes. The cells of individuals, who routinely sleep less than six hours a, start to become less receptive to insulin. This causes blood sugar levels to roar and induces a highly dangerous state of hyperglycaemia.

Should this state persist over longer periods of time, your body will shift towards a pre-diabetic state, which will ultimately grow into the blood-sugar induced abomination, known as type 2 diabetes. [19]


Sleep and fertility

Scientists from the University of Chicago have decided to conduct an experiment on young adults, so as to get a clue on the implications of sub-optimal sleep time on fertility.

The testosterone virility of these young males in their mid-twenties has, after just one week of about five hours of sleep each day, effectively aged said sleep-deniers by ten to fifteen years. [20]

Women are not exempt from those fertility-endangering effects. If you are female, then routinely catching less than six hours of sleep each night will cause your follicular-releasing hormone to drop by 20 percent. Furthermore, if you are a woman, and tend to work at unusual hours, you are 80 percent more likely to suffer from sub-fertility, which diminishes your probability of conception. [21]


Sleep and your immune system

Your immune system also takes a hit, when you decide to skip parts of this crucial third of your day.

There exists a clear, linear relationship between the amount of sleep that one individual is getting and their infection rate. Sleep around five hours on average, and the rate of infection, in terms of susceptibility to catching a cold, raises to 50 percent, as compared to those, who get around seven hours of daily sleep (they hover around an 18 percent chance of infection). [22]


Sleep and cancer

Studies conducted by Dr. Irwin at the University of California have revealed, just how detrimental a loss of sleep can be, if one takes a closer look at the cancer-fighting immune cells.

This expert has shown that just a single night of only four hours of sleep – that is going to bed at 2 a.m., and waking up at 6 a.m., as an example, can decrease the expression of these supportive biological constructs by a whooping 70%. You don’t need to be a genius, to imagine the perilous ramifications of this shortage of natural killer cells, which may rear their ugly heads after just one week, let alone months or even years of sub-performance in the realm of refreshing slumber-time.

Epidemiological studies have demonstrated that night-time shift work, and the induced disturbance of the circadian rhythm, significantly increases your propensity towards developing numerous forms of cancer, such as cancer of the breast, the prostate, the uterus wall or the colon.

It is no wonder that the World Health Organization has classified a lack of sleep as “probable carcinogen” [23], if one takes a closer look at its molecular implications. Deprive yourself of your much needed Z’s and the amount of your tumor-associated macrophages, – so-called “M1 cells” – which combat cancer, gets diminished. At the same time “M2 cells”, which conversely promote cancer growth, experience a boost in their numbers.


Sleep and genetic deviations

If the foregoing adversities weren’t enough, a shortage of sleep even manages to eradicate the biological foundation of your very existence itself.

Dr. Derk-Jan Dijk has stumbled upon an unsettling predicament: get around 6 hours of sleep for a week and the activity of about 700 genes gets twisted. This abnormal expression causes the activity of half of those genes to rev up, whereas the activity of the other half gets diminished.

Sleep loss also causes the capstones of your chromosomes – namely telomers – to deteriorate. Those microscopic protectors shield those vital molecular constructs. They are, at least in part, responsible for your health, respectively age.

6) Sleep disorders

As of right now, there exist around a 100 known sleep disorders. Some of them cause their victims to be unable to fall asleep entirely, whereas others may lead them to committing crimes. I have decided to outline three of those disorders.



Disorders within this array are related to movement.

  • Sleep = somnus
  • Movement = ambulation

Sleepwalking, sleep talking, sleep eating, sleep sex, and even sleep homicide are unfortunate results of this abnormal state of slumber. These events spring from the deepest stage of non-dreaming (NREM) sleep.

Individuals who have been diagnosed with this condition get stuck between wakefulness and sleep – a state of mixed consciousness, so to speak. They are asleep, yet capable of performing basic rehearsed action patterns, such as walking and interacting with their environment, or babbling a few words/sentences.


In 1987 an extreme case, related to somnambulism took its turn in the United States of America. The twenty-three-year-old Kenneth Parks, who was by no means a violent man, has suffered from severe insomnia due to worries caused by joblessness and gambling debts.

After he fell asleep on his couch, at 1:30 a.m., he arose, got in his car and drove approximately fourteen miles to the residence of his mother-in-law, stabbed her to death with a knife, which he had picked up in the kitchen. Afterwards he attacked his father-in-law with a cleaver and strangled him into unconsciousness.

Later on, he got back into his car, and after snapping out of his trance-like state, he drove to the next police station and confessed that he might have killed someone, for blood ran down his arms, since he severed his own flexor tendons with the knife.

He was not culpable for his actions, for he has suffered a severe case of sleepwalking, whilst committing this heinous act.


Examples such as this one are certainly outliers, but are nonetheless perfect demonstrations of sleeps’ implications on our everyday being.



Individuals who suffer from this prominent malady, are simply incapable of generating sufficient sleep in the antics of quality, and time.

There are basically two types of insomnia:


I) Onset insomnia

Sufferers have problems, when it comes to falling asleep.


II) Maintenance Insomnia

Sufferers experience difficulties, when it comes to staying asleep.


By the way, these two types are not mutually exclusive.

On average, one out of nine people fall within the group of insomniacs. If one of your parents suffer from this illness, you have a 28 – 45% chance of being on the receiving end.

Other factors, which may contribute to this undesirable cause, include, among others, too much bright light during the night, caffeine, tobacco, and the wrong room temperature. But more on that later on.

Internal triggers are mostly related to emotional worries and anxiety. These negative feelings cause our sympathetic nervous system to overreact. This abnormal physiological state expresses itself basically in four different ways.


I) A raised metabolic rate, which in turn leads to a higher core body temperature. In order to initiate sleep, our core body temperature must drop by a few degrees.


II) Heightened levels of the stress hormone cortisol, and the neurochemicals adrenaline and noradrenaline. These protein complexes raise your heart rate, which further increases your metabolic rate.


III) Your brain activity

Certain departments of your brain express themselves in abnormal ways. More specifically, those related to the generation of emotions and the recollection of memories. The amygdala and the hippocampus shows no such maladjusted patterns during sound sleepers.

To put it bluntly: Insomniacs are incapable of disengaging from internal motives related to altering, worrying and ruminating.


IV) Sleep quality

Sufferers’ electrical brainwaves during deep NREM sleep is overall shallower and less energetic. On top of that, their REM sleep is highly fragmented and interspersed with brief bouts of wakefulness.


This leads them to wake up feeling unrefreshed, which lowers their overall functionality. Insomnia is henceforth a 24/7 illness.


Fatal Familial Insomnia

This maddening illness keeps its caged homo sapiens in a deadly continuum of wakefulness. This genetic inheritance leads to the death of the respective carrier.


Take Michael Corke, as an example. He was a highly energetic, active being, a devoted husband and a teacher, who began having troubles getting his slumber at the onset of his fortieth year on earth. It all started out in a rather trifling way. At first he blamed his wife’s snoring for his lack of sleep, which wasn’t the case after all, for he has decided to sleep on the couch for the next ten nights.

After seeking out medical help – which was, unsurprisingly – to no avail, and only resulted in the diagnose of unrelated sleep-disorder, his insomnia became worse and he started getting no sleep whatsoever. This final destination caused him to progressively decline in a myriad of ways.

No sort of external intervention allowed his brain to lessen its grip on wakefulness.

After eight weeks of no sleep, his cognitive wheels started getting rusty at an alarmingly fast rate. His body deteriorated as well. His motoric skills were so compromised that he wasn’t even able to walk in a coordinated and coherent manner.

When he had to conduct an orchestral performance at his school, Michael was able to make it through the orchestra and climb atop the conductor’s rostrum at a frightening slow pace – it took him several cane-assisted minutes.

As he started getting closer to the six-month mark of a complete lack of sleep, death drew nigh. Although he was still a somewhat young human, his neurological state was tantamount to an elderly individual, who arrived at the last stage of dementia.

He started getting hallucinations. The young American also lost his ability to bathe and clothe himself. He “forgot” all skills related to using language. Rudimentary movements with his head and rare, nonsensical utterances, were his only means of communication.

Soon afterwards, he entered “eternal” slumber…


Every patient diagnosed with this neurological abomination has died within ten months. There are no ways of saving these poor souls, as of right now.

An anomaly of a gene – PrNP – which stands for prion protein, is the reason for this fatality. A rogue version of this protein results in a mutated version and eventually propagates itself in the form of an unstoppable virus. This crooked aberration rapidly targets certain areas of the brain and basically erodes them.

One such region of attack is that of the thalamus – our sensory gate, which needs to be shut, in order to end wakefulness and initiate sleep. Examinations of those in the early stages of this disease have displayed grim premonitions: thalami akin to swiss cheese. Most prominently in the outer layers of this crucial structure. These layers form the sensory doors, which are supposed to close shut every night, so as to fall asleep.

The thalamus is thusly perpetually stuck in a perceiving state and therefore unable to allow the mind to soothe into the revitalizing depths of unconsciousness.


Too much and too little sleep

Epidemiologic studies suggest that mortality risk and sleep are tightly interwoven. The relationship between those two is, however, not linear.

We need to get an adaptive balance between wakefulness and sleep, whose sweet spot lies, in the case of homo sapiens, in relation to wakefulness at sixteen hours, and in terms of sleep at around eight hours.

Too much sleep is detrimental as well.

This reverse-J-shape shows that too much sleep may be just as bad as too little sleep. Get more than 9 hours and adversity will overpower the rejuvenating effects of slumber and turn them around.


Sleep and ethics

Depriving yourself of sleep not only causes you to lose the ability to accurately recall memories, become emotionally unstable (which prevents logical thought and even basic verbal comprehension), it even leads to worse implications.

Deviant behavior and increased rates of lying, dishonesty and henceforth deceitful actions, also spring from the rotten hotbed of sleep deprivation. [24]

7) Sleep interferences and interventions

Nowadays it is not hard to distract ourselves. Most individuals not only “procrastinate” on their sleep, but also actively destroy the cogs of this ingrained mechanism.

We are polluting our sleep by means of electric light, temperature, caffeine, alcohol and a history of shift work.


Light and/or flight

We are a predominantly visual species. More than two-thirds of our brain are devoted towards processing visual influx. Artificial light has allowed us to stay up longer than intended by nature, yet comes with a slightly unsettling downside.

Our visible light spectrum spans from shorter wavelengths (approximately 380 nanometers), which express themselves in cooler colors, such as violets and blues, to longer wavelengths (approximately 700 nanometers), which manifest themselves in warmer colors, such as yellow and red.

Sunlight consists of a mixture between all sorts of wavelengths. Lost daylight prompts our suprachiasmatic nucleus to “inform” the pineal glands that night has dawned. This, in turn, causes the pineal gland to release melatonin. The powerful hormone signals our brain and body that it is time to go to bed.

Artificial evening light delays the release of melatonin. Even small influences, in the realm of 8-10 lux have shown to suppress this release.

By the way, small bedside lamps’ luminous emittance ranges typically between 20-80 lux.

A subtly lit living room’s light hovers at around 200 lux. This emittance’s strength is only akin to about 1 to 2 percent of the sun’s radiation, yet it suppresses the release of melatonin by around 50 percent. The same goes for your iPad.

Use this technical device for reading, instead of a traditional book, and your melatonin release will be suppressed as well by a staggering 50 percent.

We react more severely to shorter wavelengths. The evolutionary reason behind this heightened influence on our hormonal release is one, which can be attributed towards our stemming from the aquatic regions of our earth.

The ocean filters light and strips away most longer wavelengths. What remains are the cooler colours, in relation to the spectrum of light.

The usage of LED devices impacts our natural sleep rhythms, its quality and our overall alertness throughout the day and should be used properly, so as to diminish their ramifications on our night’s shut eye.

Besides, maintaining complete darkness throughout the night is critical too. You can take care of these two obstacles, by installing blackout curtains and software on your computers, phones and tablets, so as to reduce the blue-light.


Booze – no snooze

Alcohol, probably the most often used sedative around the globe, acts as a powerful suppressor of the prefrontal cortex. It therefore inhibits our rationality, logic and makes us more social. We become more extroverted and loosen up, but as time goes on, its inhibiting effects reach other parts of our brain.

We start getting more sluggish. Our consciousness takes a hit and the electrical brainwave state, as brought upon by this sedative, is not the same as that of natural sleep. Its state is tantamount to a light version of anesthesia.

If this wasn’t enough, alcohol distorts your sleep in two ways:


I) Sleep fragmentation

Your sleep gets split up and is henceforth not restorative. Most drunken individuals do not even notice their frequent bouts of awakening, for they occur unnoticed most of the time. They also do not remember them.


II) REM Sleep suppression

This mass produced sedative poses as one of the most influential suppressor of our creativity-enhancing state of slumber. The metabolization of alcohol produces chemical by-products; namely ketones and aldehydes.

The latter hold the most ravaging ramifications for REM sleep, for they block our brain’s capability of generating said state of slumber.

Even moderate amounts are enough to trigger this negative feedback loop.


Alcoholics are especially endangered, for their lack of REM sleep causes an internal buildup of REM-sleep pressure. This clogged pipe oftentimes bursts and expresses itself in a frightening psychotic state, known as “delirium tremens”. [25]

Hallucinations, delusions, and disorientation are the result of dream-intrusions due to this pent-up pressure.


Its implications on learning and the formation of memories are just as terrifying.

Scientists have conducted a 7 day study with three groups of people.

On the first day all 3 groups have learned a novel grammar, much like a new coding language, or algebra. This new input has been learned by everybody in a highly proficient manner – the accuracy was hovering around 90 percent.

All three groups have been tested after six nights of intervening sleep, so as to ascertain, how much of this new input has been solidified. What differentiated those three masses of individuals, was the type of sleep they had.


The Experiment


Group A:

  • Control group
  • Natural and full sleep


Group B:

  • Got slightly drunk shortly before (and only on) the first night after learning during daylight
  • 2-3 shots of vodka, mixed with orange juice
  • Standardized blood-alcohol amount according to their gender, bodyweight


Group C:

  • Were allowed to sleep naturally on the first and second night after this novel input
  • Got similarly drunk before bed on the third night


Now please note that all three groups have learned this new input on day 1, whilst being sober and they were tested on day 7, in a state of sobriety, as well.


The results:


Group A:

  • Remembered everything
  • Even showed an enhancement of abstraction and an upkeep of knowledge, in comparison to their initial stages of learning


Group B:

  • Suffered from partial amnesia, roughly speaking
  • Forgot more than 50 percent of their initially gained knowledge

This clearly shows, as previously mentioned, that our brain needs quality sleep the first night after learning something new, so as to process new memories.


Group C:

  • Suffered from partial amnesia as well
  • Forgot 40 percent of the initially gained knowledge


This is the most interesting find. Your memories are not completely solidified after only one night of sleep. Alcohol and the impending lack of quality sleep – and any sort of disruption of sleep, for that matter – retroactively inhibits your consolidating process of newly gained memories.

Practically speaking, if you were to learn for an exam and you would start doing so on Tuesday, but would go to the club on Friday and get intoxicated, even just a little, you would forget a lot of the previously accumulated pieces of knowledge, although you have had three nights of sleep in between.


Thermal hotspot

In order to successfully enter the realms of unconsciousness, our core body temperature needs to drop by around 1 degree Celsius, respectively 2 to 3 degrees Fahrenheit.

This detection occurs in thermosensitive cells within our hypothalamus, which are located right next to the suprachiasmatic nucleus. This allows the cells to effectively communicate with our internal clock and henceforth signal the arrival at this optimal sleeping condition.

The release of melatonin goes not only hand in hand with the onset of dusk, but also with the temperature loss, which occurs naturally as a result of the setting sun.

Heat dissipates mostly from our extremities. That is, our hands, feet and head. This might also explain, why we are so prone to sticking our feet out of the blankets, whenever we go to bed.

A similar cooling effect occurs, when we take a shower. As the water on those spots evaporates, heat dissipates as well, thereby lowering the temperature of our core, so to speak.

The evolutionary background can be traced back to the eastern equatorial regions of Africa. This continent shows a great discrepancy between the temperatures experienced throughout the day and the night. Our predecessors did not have the means to artificially cool, respectively heat up their shacks and therefore developed a sort of thermic harmony with their environment, as a result of this natural ebb and flow between the temperatures of day and night.

By the way, the optimal temperature of your bedroom (assuming standard bedding, that is), lies around 18.3 °C, respectively 65 degrees Fahrenheit, for the average joe. Of course your individual physiology, gender, and age also need to be taken into account, but it is nevertheless a good number to aim at.

Another tip is to take hot showers/baths before you go to bed. Healthy adults can increase their deep NREM sleep by about 10 to 15 percent. [26 | 27]


Rude awakenings

No other species is artificially terminating their sleep. This harmful intervention brought about by the dawn of the industrial era comes with a few startling side effects.

If your body gets woken up by an alarm, the physiological state has to endure an abrupt shock, which leads to a spike in blood pressure, an accelerated heart rate – which stems from an explosive burst of activity caused by the fight-or-flight branch of our nervous system. [28]

An even bigger danger disguises itself as the unseemingly snooze button.

After having been wakened up once in this nonchalant manner, the physiological state of your body becomes abnormal, as previously mentioned. Now rinse and repeat this for a few days a week, for the majority of your life, and you can see, where this is going.

There is no merit to be found in a self-inflicted cardiovascular assault. You should, therefore, take heed to stand up immediately after your alarm has woken you up (if you cannot do so without one, in the first place, that is).


Deceitful sleeping pills

Many individuals try to artificially enhance their sleep, yet the pay off for this type of external ailment is oftentimes bigger than the benefit.

Modern-day sleeping pills, such as zolpidem (brand name Ambien) and eszopiclone (brand name Lunesta), induce brainwave activities, which are, frankly speaking, lackluster at best, in comparison to their natural counterparts.

These external medications generate an electrical type of “sleep”, which misses the largest, deepest brainwaves. [29]

A few negative implications come with this pharmacological wolf in sheep’s clothing. Next-day grogginess, daytime forgetfulness, conducting actions at night, many of which you are not even aware of, as well as slower reaction times, which may impact motoric skills, such as driving.

This may induce a vicious downward spiral. Your grogginess may lead you towards taking in caffeine, which in turn makes it harder for the respective individual to fall asleep at night, and may henceforth prompt the homo sapiens in question, to take in more of this nebulous pharmaceutical panacea.


A bunch of pills.

Sleeping pills come with a few nasty side-effects.

Besides, rebound amnesia may also rear its ugly head. After you stopped the intake of these medications, you will most likely experience even worse sleep than beforehand. This is an immediate result of altered brain receptors as a reaction to the heightened drug dose, due to the brain attempting to become somewhat less sensitive as a means of countering the foreign chemical substance within its boundaries. This buildup leads to a common phenomena, known as “drug tolerance”.


After stopping the supplication, the withdrawal process kicks in and, in turn, leads to a rather uncomfortable spike in insomnia severity.

On top of that, many individuals, who take in sleep medications, experience only slight improvements in their sleep. And even those minuscule improvements are more subjective than objective.

Sleep recordings have shown that there was virtually no distinction between the placebo and the sleeping pills, in regard to how soundly the human beings slept.

Both the placebo and the prescribed medications have only reduced the time necessary to fall asleep by about ten and thirty minutes, yet this change showed no statistically significant differences between those two groups. To state it in other words: There was no objectively improvement of sleep, as offered by these sleeping pills, beyond that of a placebo. [30]

They are even harmful, as some studies show.

Natural deep sleep helps solidify new memory traces within our mental faculties. This requires the active strengthening of connections between synapses, which make up a memory circuit.

It has been found that Ambien has caused to not only fail to match these naturally induced benefits, but also to weaken the brain-cell connections by about 50 percent, which have formed during the process of accumulating more knowledge.

This alleged ailment has henceforth turned out to be a memory eraser.

If similar findings emerge, we have to acknowledge that they may help individuals to marginally fall asleep faster, but upon wakening up, cause those same humans to have lost more memories.

Other than that, those medications prove themselves to be especially dangerous during pregnancy. It is believed that dependence and withdrawal symptoms of infants, whose mothers take in these supposed goodies, occur during the postnatal period. [31]

If this hasn’t been alarming enough, Dr. Kripke has found a strong correlation between an increased mortality risk and sleeping pills. Individuals, who use those prescribed sleeping aids, are also more prone towards developing cancer. [32]

As you can see, even moderate usage heightens your risk of mortality. So tread lightly.

Now let me state this: I am not against pharmaceutical interventions. I just believe that there are currently no such sleep-related treatments available, where the benefits far outweigh the risks.


Helpful interventions

Currently the most effective treatment for bettering one’s sleeping disarray can be found within the realm of therapy. CBT-I, or cognitive behavioural therapy for Insomnia, is being rapidly accepted by the medical community as the first ray of light amidst the deep sea of available ailments.

The standard procedure of bettering one’s sleep, in terms of this therapy, encompasses the following parts:

  • reducing caffeine and alcohol intake
  • removing screen technology from the bedroom
  • cooling the bedroom
  • establishing a regular bed-time and wake-up time, even during weekends
  • going to bed only when sleepy
  • avoiding sleeping on the couch early/mid-evenings
  • never lie awake in a bed for a prolonged time; get out of bed, doing something different, when the urge to sleep returns
  • avoiding daytime napping, if you experience difficulty falling asleep at night
  • reducing anxiety-provoking thoughts and worries by learning to mentally calm down before bed
  • removing visible clock-faces from view before getting to bed, so as to reduce the anxiety, which arises due to an incapability of getting asleep in a swift manner


General interventions [33]
  • sticking to a sleep schedule
  • avoid exercise two – three hours prior to going to bed
  • avoid caffeine and nicotine
  • avoid alcoholic drinks before bed
  • avoid large meals and beverages late at night
  • avoid medicines that delay or disrupt your sleep
  • don’t take naps after 3 p. m.
  • relax before bed
  • take a hot bath before bed
  • Make your bedroom dark, cool and create a gadget-free environment
  • Have the right sunlight exposure
  • Don’t lie in bed awake

8) Conclusion/Related reading

Sleep is one part of the puzzle of your life that you definitely do not want to cut short. As it stands now, our society as a whole does not appear to be recognizant of the impeding dangers that lurk within the shallow depths of a lack of sleep.

If you are somebody, who’s got a friend or two, who always boldly states that “sleep is for the weak”, please refer them to this article, so as to raise the awareness necessary, for a tidal shift in our slumber-related thinking.

I hope you have thoroughly enjoyed this article and are now more wary in your sleep practices.

At this point, I would like to mention Dr. Matthew Walker. Without his resources, I would not have been capable of writing this guide. He has written an absolutely brilliant and far more extensive piece of literature on the underlying principles of sleep, than I could possibly present to you. I therefore highly suggest you order his book “Why we sleep”. The link(s) to this scientific masterpiece can be found below.

If you wish to be immediately notified, whenever a new article has been published, please consider subscribing.

9) References
  1. Light Responsiveness of the Suprachiasmatic Nucleus: Long-Term Multiunit and Single-Unit Recordings in Freely Moving Rats
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  2. Erland, L. A. E., & Saxena, P. K. (2017). Melatonin Natural Health Products and Supplements: Presence of Serotonin and Significant Variability of Melatonin Content. Journal of Clinical Sleep Medicine : JCSM : Official Publication of the American Academy of Sleep Medicine13(2), 275–281.
  3. Vosko, A. M., Colwell, C. S., & Avidan, A. Y. (2010). Jet lag syndrome: circadian organization, pathophysiology, and management strategies. Nature and Science of Sleep, 2, 187–198.
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  7. E.J. Mulder, L. P. Morssink, T. van der Schee, and G. H. Visser (1998), Acute maternal alcohol consumption disrupts behavioral state organization in the near-term fetus, Pediatric Research 44, no.5: 774-79
  8. Mennella, J. A., & Garcia-Gomez, P. L. (2001). Sleep disturbances after acute exposure to alcohol in mothers’ milk. Alcohol (Fayetteville, N.Y.)25(3), 153–158.
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  14. D. A. Ciraulo, J. Piechniczek-Buczek, and E. N. Iscan, “Outcome predictors in substance use disorders”, Psychiatric Clinics of North America 26, no. 2 (2003): 381 – 409
  15. J. T. Arnedt, D. A. Conroy, and K. J. Brower, “Treatment options for sleep disturbances during alcohol recover”, Journal of Addictive Diseases 26, no. 4 (2007): 41 – 54
  16. Jessen, N. A., Munk, A. S. F., Lundgaard, I., & Nedergaard, M. (2015). The Glymphatic System – A Beginner’s Guide. Neurochemical Research, 40(12), 2583–2599.
  17. Nagai, M., Hoshide, S., & Kario, K. (2010). Sleep Duration as a Risk Factor for Cardiovascular Disease- a Review of the Recent Literature. Current Cardiology Reviews6(1), 54–61.

  18. O. Tochikubo et al, Effects of insufficient sleep on blood pressure monitored by a new multibiomedical recorder, Hypertension 27, no. 6 (1996): 1318-24

  19. Zhilei Shan et al, Sleep Duration and Risk of Type 2 Diabetes: A Meta-analysis of Prospective Studies, Diabetes Care 2015 Mar; 38(3): 529-537

  20. Leproult, R., & Van Cauter, E. (2011). Effect of 1 Week of Sleep Restriction on Testosterone Levels in Young Healthy MenFREE. JAMA305(21), 2173–2174.


  22. Prather, A. A., Janicki-Deverts, D., Hall, M. H., & Cohen, S. (2015). Behaviorally Assessed Sleep and Susceptibility to the Common Cold. Sleep38(9), 1353–1359.

  23. Erren, T. C., Falaturi, P., Morfeld, P., Knauth, P., Reiter, R. J., & Piekarski, C. (2010). Shift Work and Cancer: The Evidence and the Challenge. Deutsches Ärzteblatt International, 107(38), 657–662.
  24. C. M. Barnesa, J. Schaubroeckb, M. Huthc, and S. Ghummand, “Lack of sleep and unethical conduct,” Organizational Behavior and Human Decision Processes 115, no. 3 (2011): 169-80

  25. Brower, K. J. (2001). Alcohol’s Effects on Sleep in Alcoholics. Alcohol Research & Health : The Journal of the National Institute on Alcohol Abuse and Alcoholism25(2), 110–125.

  26. J. A. Horne and B. S. Shackell, “Slow wave sleep elevations after body heating: proximity to sleep and effects of aspirin,” Sleep 10, no. 4 (1987): 383 – 92.

  27. J. A. Horne and A. J. Reid, “Night-time sleep EEG changes following body heating in a warm bath,” Electroencephalography and Clinical Neurophysiology 60, no. 2 (1985):154-57


  28. K. Kaida et al., „Self-awakening prevents acute rise in blood pressure and heart rate at the time of awakening in elderly people”, Industrial Health 43, no. 1 (January 2005): 179-85

  29. E. L. Arbon, M. Knurowska, and D. J. Dijk, „Randomized clinical trial of the effects of prolonged release melatonin, temazepam and zolpidem on slow-wave activity during sleep in healthy people”, Journal of Psychopharmacology 29, no. 7 (2015): 764-76

  30. Huedo-Medina, T. B., Kirsch, I., Middlemass, J., Klonizakis, M., & Siriwardena, A. N. (2012). Effectiveness of non-benzodiazepine hypnotics in treatment of adult insomnia: meta-analysis of data submitted to the Food and Drug Administration. The BMJ345, e8343.

  31. J. MacFarlane et al., „Hypnotics in insomnia: the experience of zolpidem”, Clinical Therapeutics 36, no. 11 (2014): 1676-1701

  32. Kripke DF, Langer RD, Kline LE

    Hypnotics’ association with mortality or cancer: a matched cohort study

    BMJ Open 2012;2:e000850. doi: 10.1136/bmjopen-2012-000850

  33. Tips for Getting a Good Night’s Sleep



  1. Figure showing body temperature: Matthew Walker – “Why we sleep”
  2. Figure showing melatonin-levels: Matthew Walker – “Why we sleep”
  3. Figure showing circadian rhythm and sleep presssure: Matthew Walker – “Why we sleep”
  4. Figure showing sleep phases: Matthew Walker – “Why we sleep”
  5. Figure showing brainwave activity: Matthew Walker – “Why we sleep”
  6. Figure showing correlation between sleeping pills and mortality risk: Matthew Walker – “Why we sleep”
  7. Figure showing reverse J-shape; modified: Matthew Walker – “Why we sleep”

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