Why We Sleep?

Unlocking the power of sleep dreams with Matthew Walker, PhD.

Wanted to do a different sharing this time. Normally I either post travel related stuff -which is 90% of all the content- or fashion related things that I like. Even though I broke the ice a couple of months ago by sharing one of the projects of a data science certificate bootcamp, I have never posted things about a book I read. This very interesting one called “Why We Sleep” from Matthew Walker; a UC Berkeley Professor of Neuroscience and Psychology was really worth mentioning though.

As you can guess, this 368 page book is pointing out almost all the reasons to “Why We Sleep”. It explains why sleeping isn’t “just” sleeping; the only connection isn’t our energy levels but it takes up a substantial role in preventing us from different diseases as well as propping up an abundant number of our capabilities. Readability might sound a bit intimidating at first; especially if your first perception is receiving medical explanations with descriptions in latin language. Well, even though there are a lot of medical explanations, this book is nowhere near being a hard read that gives you headaches.

Instead of explaining the book cover to cover, I’ll try to point out what really took my attention, and hopefully this won’t only make this piece an easy read, but also help people who don’t have time to read it understand the importance of sleep.

Why We Sleep – Book Cover

“Fatality rates of drowsy driving accidents exceed alcohol and drugs combined in the US.”


So to start with; the author claims that there are two factors counting into why we want to sleep:

1) Circadian Rhythm aka Body Clock

2) Sleep Pressure: Adenosine

Circadian rhythm is basically your 16 hour awake – 8 hours sleepin cycle. Even though it depends from person to person, every human being goes through this circle every day. There is a misperception that we sleep after sunset and wake up after dawn; that isn’t the real case indeed. In order to claim that this perception isn’t right, two researches called Nathaniel Kleitman and Bruce H. Richardson stayed in a cave for 32 days in 1938. They claimed that even when there is no light, our bodies follow a certain sleeping pattern, which is actually the Circadian Rhythm.

Alertness During the Day

Adenosine, on the other hand is a chemical that starts producing in your brain when you wake up in the morning that reaches its peak before midnight causing sleep pressure. Well, you might be wondering of another chemical called “Melatonin” that is widely believed to affect sleep; the author claims that it’s just like the sprint contest clapper that shows the race start. It doesn’t have any direct effect on sleep.

Sleep Pressure – Adenosine Levels


Most of you are probably well aware of the phenomena called “Jet Lag” that messes up your sleep circle when traveling between different time zones. The simple explanation to that is lying under “Circadian Rhythm” as well. As in the cave experiment, whatever you do when you travel between time zones don’t allow you change your body clock. Also, not to forget, “Circadian Rhythm” tends to be longer when shut out of outside influences such as sunlight.

Another interesting thing to know about “Jet Lag” is actually related to which direction we change time zones towards. When we fly towards west, we are usually less affected by jet lag, because the day gets longer. It’s always easier to stretch the day than to shrink it.


One of the most important things I read in the book was about my staple drink, coffee. I always wondered the story behind “caffeine” to understand how it kept me awake. It has a very simple explanation indeed.

There is a little part of the brain called “Thalamus”. This small part is our sensory gate, and all our senses go through this gate before they reach our brain and get interpreted. So what caffeine basically does is blocking adenosine before reaching this gate. It keeps producing in our brain while we are taking caffeine, but it’s blocked to cause sleep pressure. When you stop caffeine which takes multiple hours to lose its effect, we feel sleep pressure even more than we normally would.

Another interesting thing about caffeine is an experiment where its effects are tested on a spider along with other harmful chemicals. As you can see in the below picture, it seriously impacts how the spiders build their webs.

Spider vs. Chemicals


– Relationship between the size of nervous system, complexity of nervous system, and total body mass are predictors of sleep time. Increasing complexity relative to body size result in greater sleep.

– REM sleep. Some mammals don’t have it, or have it in a different way.

– Some animals go to sleep partially; when birds immigrate 50% of the brain is sleeping.

– Food. Scarcity of food will make you sleep less as the brain is tricked into thinking scarcity.


Beware of it or not, there is a term called “Greek Siestas”, which represents Greek people taking midday naps or going to work late. There are some people in Greece living in rural areas, who are described as “forgot to die”. So in order to understand whether there is any relation to sleeping patterns of these people, they were asked to skip these sleeps. In a 6 year period, the numbers of heart diseases among these people increased 37%.


Most of you might have heard of two different stages of sleep; Non-rapid Eye Movement(NREM) and Rapid Eye Movement(REM). NREM is the dreamless state of sleep, where brain waves, breathing are slow, and the heartbeats are regular consisting 75% of the total amount of sleep we get everyday. REM on the other hand, is the unique portion of our sleep where our vivid dreams happen. The name “Rapid Eye Movement” was given after the discovery of Eugene Aserinsky in 1953, a sleep researcher, figuring out our eyes were moving at this specific interval of our sleep.

Sleep Cycles

Coming to the differences between these two stages taking turns; NREM is mostly about moving data we processed at the daytime from short-term memory to long term memory. So this is one of the greatest signs the author points at while trying to explain the significance of sleep. If you don’t get enough sleep, you totally can’t make new memories.

Connected to NREM’s memory making responsibility, REM not only strengthens new memories, but also helps creativity and problem solving. As author points out, average human sleep is shorter than average animal sleep but humans have a longer REM period; 25% to 9%. This is actually the main explanation to our sociocultural complexity and cognitive intelligence being lubricated by REM sleep and taking us to the top of the evolution pyramid.


We all believe that as people age, they need less sleep that is somehow related to having an older body, and changing chemical composition of the body. Well, that’s not really the case.

Old man asleep

There are three main reasons why elder people sleep less:

1) Change in Circadian Rhythm; elder people don’t always stay awake for 16 hours and then sleep like comparably younger people.

2) Because of health issues, they visit bathroom more frequently, and that causes interruptions to their sleep patterns.

3) Elder people lose the ability of producing deep sleep, as per their patterns of sleep going as far as sleep deprivation -which I will mention soon- in their earlier life.

“Napping after learning something gave 20% advantage over not sleeping.”


So the part where author talks about the actual causes of sleep deprivation, there were a couple of significant quantitive facts, which I should totally share:

– 6 nights of 4-hour sleep causes a feeling of not having slept for 24 hours on the 7th day

– 11 nights of 4-hour sleep causes 48 hours of non-sleep symptoms

– 10 nights of 6-hour sleep causes 24 hours of non-sleep symptoms.

But the worst of all is yet to come:

People just don’t realize how their perennial state of sleep deficiency has come to compromise their mental aptitude and physical vitality including the slow accumulation of health.

Battery About to Die

There was one other interesting fact that most of us can relate to our experience:

“Wake up at 7am, go party until 2 am with friends; you are in a mental state above alcohol limits for driving in the US (%0.08).”


A Rare Species

The author brings up an interesting fact about a very very little portion of individuals. Scientific evidence shows that people with the gene called BHLHE41 seem to survive on 6-hours of sleep, and they wake up after this interval even if there is no trigger around to wake them up. Scientists are also trying to figure out what’s so special about this gene, so the explanation is yet to come. I can see your excitement on being one of these rare people, but the author warns that the probability of a human being holding this gene is as little as winning lottery on the new year’s eve.

“There is no scientific evidence that a drug, device, or psychological willpower that can replace sleep. Neither naps, nor caffeine can salvage more complex functions of the brain, including learning, memory, emotional stability, complex reasoning or decision-making.”

Are you short tempered or throwing tantrums out of the blue?

Amygdala, an almond shaped cluster inside the brain, is also a key hot spot for triggering strong emotions such as anger and rage. More importantly it is linked to the fight or flight response. It showed well over 60 percent amplification in emotional reactivity in the participants who were sleep deprived. So if you are short tempered or throwing tantrums out of the blue, you might want to analyze how much sleep you get compared to what genetics you have.


“If you don’t sleep the very first night after learning, you lose the chance to consolidate those memories, even if you get lots of “catch-up” sleep thereafter.”


Alois Alzheimer

Alois Alzheimer, a German psychiatrist and neuropathologist who lived between 1864 and 1915, was the first person to publish a case called “presenile dementia” famously known as Alzheimer disease today. It basically degenerates brain and causes memory loss.

Alzheimer Visualized

Found in every one of two human beings over age 70, Alzheimer disease gives highest of its credits to sleep deprivation. Without sufficient sleep, amyloid plaques build-up in the brain, especially in deep-sleep-generating regions, attacking and degrading them. The loss of deep NREM sleep caused by this assault therefore lessens the ability to remove amyloid from brain at night, resulting in greater amyloid deposition. Getting less sleep will surely increase the risk of developing Alzheimer’s disease.


Scientific evidence shows that adults forty-five years or older who sleep fewer than six hours a night are 200 percent more likely to have a heart attack or stroke during their lifetime.


Most people think nothing substantial would happen out of losing an hour sleep for a single night, believing it to be trivial and inconsequential. It is anything but.


Author says, they discovered that supervisory regions in the prefrontal cortex required for thoughtful judgments and controlled decisions had been silenced in their activity by their lack of sleep, causing obesity.


Those sleeping five hours on average, had an infection rate of cold and flu around 50%. On the contrary, those sleeping 7 hours, had an infection rate of 18%.

“World Health Organization classified nighttime shift as probable carcinogen (cause of cancer).”

Sleep-loss, Genes, DNA

Two individuals of the same chronological age would not appear to be of the same biological age on the basis of their telomere health if one was routinely sleeping five hours a night, while other was sleeping seven hours a night.

Why Do We Dream?

Dreaming in REM Sleep

Step (1) The visuospatial regions at the back of the brain enables complex visual perception

Step (2) The motor cortex instigates movement

Step (3) The hippocampus and surrounding regions support autobiographical memory

Step (4) The deep emotional centers of the brain – the amygdala and the cingulate cortex helping generate and process emotions

Sigmund Freud

As most of you might know, Sigmund Freud, an Austrian neurologist and the founder of psychoanalysis had various theories about dreams. He consistently insisted on power of dreams and how they are important to understand our way of thinking. The author points out one underrated discovery of his, while correcting another highly popular claim.

Sigmund Freud

Underrated Discovery: “Dreams emerge from the brain, answers can only be found systematic interrogation of the brain.”

False statement: “Dreams come from unconscious wishes that had not been fulfilled.”

“Freud started to reverse-engineer dreams and interpret them, and that’s where his theories started to fall.”

Robert Stickgold, a full professor of psychiatry at the Harvard Medical School claimed that 299 dream reports were assessed, and there were only a few drops of residue proving that dreams are related to what we experience the same day; in contrary to what Freud stated. According to scientific research, not all of the dreams include daily stuff or suppressed emotions.

Benefits Of Dreaming

1) Nursing mental and emotional health

2) Problem solving and creativity

REM-sleep dreaming takes the painful sting out of difficult, even traumatic, emotional episodes you have experienced during the day, offering emotional resolution when you awake the next morning.

“Through its therapeutic work at night, REM sleep performed the elegant trick of divorcing the bitter emotional rind from the information rich fruit.”

Successful People Made Use Of Dreaming

• Paul McCartney wrote Yesterday in his dream.

• Keith Richard of Rolling Stones would keep a guitar next to his bed and write songs right after he wakes up.

• Thomas Edison: He used dreams to enhance creativity. He would put ball bearings in his hand and go to sleep on a chair. At the moment he began to dream, his muscle tone would relax and he would drop the ball bearings to the metal saucepan waking him up. He would write down what he was dreaming of.

Thomas Edison


Sleep, like food, water and oxygen, may share this relationship with mortality risk when taken to extremes. After all, wakefulness in the correct amount is evolutionary adaptive, as sleep.


So to sum up all the information above; there is one single BIG IDEA I was hoping to install into anyone who read this post. Sleeping 7 to 9 hours a day is crucial for our health, and especially going below this interval gives irreparable harm to our body, specifically our brain. I would like to thank the author Matthew Walker for preparing such a scientific research based book, as I hope my sharing made you think of reading it cover to cover. Before I put the period, I will share some advices from the last part of the book on getting a goodnights sleep! Please drop down any comments below and let me know what you think!

“Blue LED Lights are shortening our own lifetime by blocking Melatonin by replacing sunlight, so better stay away from them before you go to sleep.”

“Alcohol does not provide natural sleep, it’s akin to a light form of anesthesia. Do not use Alcohol as a sleep trigger.”

” The reason why you may occasionally stick your hands and feet out from underneath the bedcovers at night, is due to your core becoming too hot; usually without your knowledge. A bedroom temperature of 18.3C is ideal for most people.”

“The hot bath invites blood to the skin, and inner heat is moved towards there, so it helps you sleep easier.”

“Try not to exercise right before sleep, because it’ll take a couple of hours for body core to cool down.”

“Don’t go to bed too full or too hungry, shy away from diets biased toward carbohydrates. (70%)”

Hope you liked the post. For all your questions and whatnot, you can either e-mail me over, or contact me through my social media accounts.



Till next!