By James Razko
In this book summary of Why We Sleep you will learn that to maintain health and performance, you need more than 7 hours of sleep per night. And unfortunately, 1/3 of people in industrialized nations sleep less than 5-6 hours per night. Likewise, 65% of adults in the USA do not sleep the recommended 7-9 hours a day. Lack of sleep correlates with a myriad of health problems, including increased risk for heart disease, obesity, type 2 diabetes, dementia, and death. Our state of sleep has gotten so bad that the World Health Organization has labeled lack of sleep to be an epidemic affecting much of the globe.
How to Tell if You Need More Sleep
You need more sleep If you can easily go back to bed at 10–11 AM. Likewise, you need more rest if you would sleep past your wakeup time without an alarm.
Short Sleepers—The Zero Percent
Like many, you may be thinking you operate just fine with 6 hours of shut-eye. However, those that can feel rested and perform optimally with less than 7 hours of sleep are a tiny percent of the world’s population, a number so small, that if you rounded it to a whole number, it would be— zero.
More likely, you have only gotten used to being sleep deprived and have no idea how impaired you actually are. As it turns out, sleep scientists have repeatedly found humans to be very poor judges of self-performance when deprived of sleep.
Five Factors That Changed Sleep
- Electric light (especially LED emitted from screens)
- Regulated home temperatures
- Legacy off punch cards/alarm clocks.
1.) Artificial Light
Artificial light, even a small amount (8-10 lux) will trick the brain into believing the sun has not set and will delay the release of melatonin. Many people who think they have insomnia are exposed to much light at night. For example, a dim living room around 200 lux will disrupt melatonin release by 50%.
LED light found in smartphones, tablets, and computers, emit blue light that is very close to daylight. Reading for two hours an iPad before bed will suppress melatonin by as much as 50 % and drastically affect REM sleep, leave you tired. Looking at a screen before bed for two hours will also delay melatonin release for the next three days
2.) Regulated Home Temperatures
Your core temperature must drop by 2-3 degrees to fall asleep. This temperature drop, before modern heating, was aided by the natural temperature dip after dusk. The advent of controlled temperatures in homes has made it harder to fall asleep.
The hands, feet, and head are the bodies most efficient radiators. Astonishingly, across the globe humans without understanding why have been splashing water on and cleaning their faces before bed— it helps you fall asleep faster. Likewise, a hot shower before bed will help cool you off by bringing blood to the surface of your skin.
The author recommends sleeping in a cool room around 65 degrees Fahrenheit ( 18.3 degrees Celsius). Of course, individual preference will vary.
Alcohol is a sedative that increases sociability by suppressing the prefrontal cortex (the rational part of the brain). Many believe alcohol helps sleep. But, it has been shown to fragment sleep. Even more frightening is that alcohol is one of the most potent suppressors of REM sleep known to man.
In several studies, those who drank alcohol the night after learning new material suffered partial amnesia of 50% compared to those who did not drink. Surprisingly, those who drank three days after learning new material showed a 40% loss of knowledge. Those who did not drink recalled 100% of the content. Amusingly, the author jokingly recommends drinking in the morning to prevent memory loss.
Mothers drinking alcohol during pregnancy or while breastfeeding will harm their babies by suppressing the child’s REM sleep among other things. REM sleep is not optional for developing life. Suppression of REM sleep will disrupt and distort the brains development.
Caffeine works by filling adenosine receptors in the brain with caffeine molecules, which unlike adenosine molecules does not send a sleepy signal to the brain. While caffeine works to suppress the feeling of being tired, it does not stop adenosines production. Ingesting caffeine will create a backlog of adenosine, and once the caffeine is flushed from your system, you will experience the familiar caffeine crash—which is all the backed up adenosine flooding into your brains adenosine receptors.
Caffeine peaks 30 minutes after ingestion. The half-life of caffeine is roughly 5-7 hours. 7 hours after ingesting caffeine, half of it will remain in your system.
Caffeine consumption results in poor sleep.
Caffeine disrupts NREM sleep and therefore should not be given to any child as NREM sleep is critical for a developing brain.
3-4 cups of decaf will equal one cup of regular coffee.
The author recommends if you only do one thing to improve your sleep, it would be to fall asleep and wake up at the same time every day.
Using an Alarm (enforced waking) wreaks havoc on your cardiovascular system, triggering the flight or flight response, and hitting the snooze button shocks your body repeatedly. Imagine the damage that is being done over days, months and years by this torturous practice handed down from the industrial revolution. Instead of using an alarm train yourself to wake up at the same time of day, every day, so you will not need an alarm.
12 Tips for Healthy Sleep
- Go to bed and wake up at the same time every day.
- Exercise at least 30 minutes a day, but not 2-3 hours before bed.
- Avoid caffeine and nicotine.
- Avoid Alcohol
- Avoid large meals before bed.
- If possible, avoid any medicine that delays or disrupts sleep.
- Do not take naps after 3 PM.
- Relax before bed by creating a ritual like reading (a hard copy) or listening to music.
- Take a hot bath before bed to speed up your sleep onset time.
- Maintain a dark, cool room that is gadget free.
- Get sun exposure at least 30 minutes per day.
- To avoid sleep anxiety, do not lie in bed for more than 20 minutes.
Every known organism has periods of inactivity that could be called sleep. The author posits that wakefulness (activity) likely evolved out of life’s first state, sleep (inactivity).
We sleep in a biphasic cycle, alternating between NREM (nonrapid eye movement) sleep and REM (rapid eye movement) sleep every 90 minutes, beginning with NREM.
In spite of the alternating 90 minute cycle, NREM and REM sleep are not spread evenly throughout the night. Most of your NREM sleep happens at the beginning of the night, while most of your REM sleep occurs in the last few hours. For this reason, if you wake up two hours early, you will lose 60-90% of your REM sleep. Similarly, if you go to bed two hours late, you will lose much of your NREM sleep.
Besides the bi-phasic sleep cycle, hunter-gatherer tribes across the globe and entire countries like Spain, especially in hotter climates, enjoy a (siesta) bi-phasic sleep pattern, sleeping 7 hours (with 7-8 hours spent in bed at night), and taking a nap of 30-60 minutes in the afternoon.
Having evolved to take naps, most people will experience a brief lowering of alertness sometime in the afternoon, known as— postprandial alertness dip. So, avoid giving presentations after lunch. Because, no matter how entertaining you may be—fighting evolution is a losing battle.
Your internal clock, AKA your circadian rhythm, is governed by a small region found in the brain that consists of about 20,000 neurons and is known as the suprachiasmatic nucleus. The average adult’s internal clock is a little more than 24hrs: the sun and other repeating factors like temperature and exercise help to calibrate this internal clock. As you may hey experienced, this internal timer can be incredibly precise. For example, before important events, you have likely found yourself waking up a few minutes before the alarm—all thanks to your circadian rhythm.
The time you naturally would fall asleep and wake up are set by your circadian rhythm. In general, some people are wired to go to bed and wake up early ( an early bird or lark), while others are programmed to sleep and rise late (a night owl). And, many fall somewhere in between. Your tendency to rise early or late is known as your chronotype which is primarily determined by genetics. Some scientists believe chronotypes evolved to reduce the total time an entire tribe would spend sleeping, which is a very vulnerable state.
During a lifetime, your circadian rhythm changes. For example, Infants, to parents dismay, do not have a circadian rhythm at all until 3-4 months of age. And, by the age of 1, a babies suprachiasmatic nucleus is well established, resulting in happier parents as the 1-year-old will sleep for most of the night. In general, Young children tend to wake early, while pubescent children will go to sleep and wake much later than any other period of life. A pubescent teen’s circadian rhythm is shifted forward by 1-3 hours, resulting in teens experiencing peek wakefulness around 9 PM. After puberty, a person’s circadian rhythm will begin to march backward, leaving the elderly (like young children) with early sleep and wake times.
We are visual creatures. In fact, 1/3 of the brain is devoted to visual processing.
Sunlight, like most creatures, regulates our circadian rhythm. Light from the sun contains the full spectrum of visible light, from short wave blue light to long wave red light. At sunset, most of the blue light is gone, and the suprachiasmatic nucleus uses this lack of blue light to signal the release of melatonin, which makes you sleepy. Likewise, at dawn, sunlight traveling through your eyelids signals the suppression of melatonin to help you wake up.
Adenosine is a compound that begins accumulating in the brain from the moment you wake up until the time you go to bed. Gathering adenosine creates sleep pressure, AKA, the feeling of wanting to sleep. It will continue to collect for as long as you stay awake. Every night sleep purges adenosine, and the cycle is set to begin again.
Surprisingly, adenosine functions independently of the circadian rhythm. For example, if you have ever pulled an all-nighter and felt the second wave of energy in the morning, that is thanks to your circadian rhythm letting your body know it is time to wake up; meanwhile, adenosine will continue to build until later in the day when you can’t take it anymore and fall asleep.
The Two Sleep Cycles
1.) NREM Sleep
NREM sleep has 4 stages, stages 1-2 are characterized by lighter sleep, while 3-4 are the deepest and most restorative of the stages.
NREM weeds and removes unnecessary neural connections and moves short term memories to long term memory sites.
The hippocampus your short term memory center and like RAM in a computer, it has a memory limit. Once the hippocampus is full, existing short term memories will have to be overwritten to create new short term memories. It is during NREM sleep that these vulnerable short term memories are moved to safer long term memory sites.
Short naps have been shown to move short term memories to long term storage, allowing the hippocampus to clear space for new memories.
The Brains Sewage System
The glymphatic system is the sewage system of your brain. Every night during sleep the glymphatic system cleans waste with glial cells. Notably, during NREM sleep there is a 20 times increase in waste expulsion. Avoid dangerous toxins building up in your brain by sleeping more than 7 hours.
A lack of sufficient NREM leaves deposits of a toxin known as amyloid in the regions of the brain (especially the suprachiasmatic nucleus) that are responsible for deep sleep. Amyloid impairs NREM sleep, and impaired NREM sleep increases amyloid deposits in the brain, creating a downward spiral that contributes to dementia.
2.) REM sleep
Only birds and mammals have REM sleep. It is believed that during evolution, abundant REM sleep provided early humans with superior emotional brain power and creativity. The author concludes that the former is more critical to our evolutionary fitness, because, without the ability to share a creative idea, no matter hour genius it is, it would not spread.
During REM sleep the visuospatial regions, motor cortex, hippocampus, and amygdala are activated; meanwhile, your body is paralyzed, besides your eyes and necessary bodily functions, like breathing.
REM sleep is the cycle of sleep in which you dream. And, a whopping 25% of our sleep is dedicated to this dramatic state of consciousness.
REM sleep’s two main functions are:
- Remembering and integrating existing knowledge and putting this into an autobiographical perspective.
- Dissolving of painful memories.
The two core benefits of REM sleep are:
- Overnight therapy
- Problem-solving and Creativity
Creativity and Problem-Solving
While in REM sleep, the brain’s vast stores of information are seen all at once, as if viewing through an upside-down telescope. This broad view allows distant ideas to be strung together, creating new and novel ideas. On the other hand, when you are awake the brain like a telescope, can only see a narrow amount of possibilities.
REM sleep mixes new memories with old memories to create unique and novel ideas. REM sleep also constructs large associative networks that allow you to get the gist of something.
Research has shown that dreaming of a particular problem will increase your chances of solving that problem.
A person’s emotional IQ fluctuates with the amount of REM sleep. Poor sleep results in a decreased ability to recognize and manage socioemotional signals.
REM sleep also recalibrates the brain’s ability to recognize facial expressions and emotions every night. One night of poor sleep disrupts the brain’s ability to detect subtle emotions in other humans resulting in a default fear bias in underslept individuals. Consider the implications of sleepy police officers, military personnel, and doctors.
Lucid dreaming (being conscious of being in a dream and able to manipulate the dream) has been scientifically verified. The author admits he doesn’t know if lucid dreaming is harmful or a new evolution of homo Sapiens.
PTSD & REM Sleep
You must dream about a traumatic experience while maintaining adequate REM sleep to reduce its impact on your waking life. PTSD is thought to be a breakdown of REM sleep, where the brain cannot process traumatic experiences. The reoccurring dreams associated with PTSD are the brain’s attempt to dissolve the painful memory night after night. Elevated levels of norepinephrine, the fight or flight hormone, prevent the brain from maintaining healthy REM sleep.
Damages of Lost Sleep
Despite what you may want to believe, a weekend of recovery-sleep will not fix a week of poor sleep. Unfortunately, once you have lost sleep, you can never get it back or fully recover it. For example, memories you could have formed will be gone—forever.
4 hours of sleep for 6 days, is the equivalent to not sleeping for 24 hours.
11 days of 4 hours of sleep is equivalent to 48 hours of no sleep.
10 days of 7 hours of sleep leaves the brain as dysfunctional as going without sleep for 24 hours.
Sleep deficits will continue to compound for days, months and years. The unfortunate part is if you go without sleep for long enough, you will get used to being tired and believe that you are okay when actually you are very impaired.
Research has shown that if you stay awake for 19 hours, your performance will be equivalent to a legally drunk person. Combine sleep loss with alcohol and the impairments do not add up, they multiply.
If you do not sleep the night after learning something your chances to consolidate those memories are gone. It is an all or nothing process. Sleep is required for memory and learning.
If you are trying to have children make sure to get your rest as lack of sleep is correlated with infertility.
Sleeping less than 6 hours a night increases your risk for cancer by 40%, and once cancer has developed, if you are still sleeping to little, it grows at an accelerated pace.
Lack of sleep damages telomeres, the caps on the ends of your DNA.
For every day that you are in a new time zone your brain’s internal clock can only adjust by one hour. Depending on the time difference, it can take several days to get over jet lag.
Unfortunately for jet setters, repeatedly traveling through time zones (like long distance pilots) has shown to reduce the size of brain regions related to memory and learning.
Some of the worst disasters in recorded history have been caused by lack of sleep. Both the Exxon Valdez and Chernobyl were caused by sleepy operators.
Under-slept individuals experience dramatic mood swings. The author observed a 60% increase in emotional reactivity in patients amygdalas when sleep deprived. In his career, this was the most significant effect he has observed to date. A lack of rest will leave the brain prone to risk-taking, likely to see others as dangerous, and exhibit poor decision-making skills. Again, consider how dangerous, under-slept, police officers, military personnel, bankers, doctors and you are.
There is no major psychiatric condition where sleep is normal. Sleep loss and mental illness are a two-way street. Regulating sleep helps maintain mental stability, and lack of sleep will amplify or trigger it.
Losing 1-2 hours of sleep will increase systolic blood pressure and heart rate, putting stress on the cardiovascular system. For example, during daylight savings time when millions lose one hour of sleep, researchers have found that heart attacks increase significantly. On either hand when people are allowed to sleep one hour extra for daylight savings time, researchers found a decrease in heart attacks.
Weight Gain, Obesity, and Diabetes
Less than 7 hours of sleep increases the risk of weight gain, obesity, and type 2 diabetes.
Researchers found that under-slept individuals ate 300 extra calories compared to their rested selves. That is 10-15 pounds a year— every year.
Sleep loss gives you the munchies by decreasing the hormone leptin (feeling of fullness), increasing the hormone ghrelin (hunger), and increasing the number of endocannabinoids in your body.
Lack of sleep:
- Increases hunger and appetite
- Compromises impulse control
- Increases food consumption, especially high caloric foods
- Decreases feeling of satiety
- Prevents effective weight loss
One study found that 3-year-olds who sleep 10.5 hours or less had a 45% chance of being obese by the age of 7 when compared to children who slept 12 hours per night.
Researchers have found that fasting with insufficient sleep will result in a 70% loss of lean body mass. Fasting with adequate sleep (8.5 hrs) resulted in a better result of a 50% loss of fat.
Sleep also improves the health of your gut bacteria (microbiome). Lack of sleep is detrimental to the microbiome and makes it harder to absorb the necessary nutrients from food.
There are over 1.2 million accidents per year related to sleepiness— every hour someone dies of a fatigue-related traffic accident. Drowsy driving accidents exceed both alcohol and drug driving accidents combined.
A microsleep is a brief loss of consciousness due to inadequate sleep. Microsleep events are the cause of many accidents.
Consider that, a person will experience a 400% increase in microsleep events if they have only had 4 hours of sleep for 6 days.
After waking from a nap or sleep, you will experience what is known as sleep inertia, or a time when your brain is still partially asleep. You should not drive right after a nap, wait at least 15 minutes or until you no longer feel groggy.
Benefits of Sleep
Besides making you more creative and helping you remember and consolidate new information from your day, sleep also lets you to retrieve memories that you could not locate during the day. After a night of sleep, you are more likely to have that “ah-ha!” moment.
Also, if you have learned a new skill, like riding a bike, the brain, through sleep will continue to improve upon this skill even on days that you do not practice.
Practice + Sleep = Mastery (learning)
Sleep and Physical Performance
If you sleep less than 8 hours, especially less than 6 hours, the time it takes you to reach physical exhaustion drops by 10-30% and will result in a decrease in overall performance. Less sleep will result in more lactic acid buildup, reduced blood oxygen, and a decreased ability to cool your body through sweating. On the other hand, sleep accelerates recovery time, promotes muscular repair, and restocks cellular energy.
Exercise marginally improves sleep. However, this improvement is not consistent from day to day. On the other hand, adequate sleep always enhances exercise performance. And, of course, a sedentary lifestyle is bad for your health and sleep.
Naps as short as 20 minutes have been shown to offer a memory advantage.
Naps have also been shown to offer motor skill improvements after learning a task.
Napping after a night of poor sleep will increase basic concentration and wakefulness, but fail top improve learning, memory, emotional stability, complex reasoning, and decision-making skills.
Sleep maintains the immune systems.
Sleeping less than 5 hours gave study participants a 50% chance of being infected by the common cold, while those who slept more than 7 hours had an infection rate of 18%. On a similar note, those who did not sleep adequately following an administration of the flu vaccine developed only 50% of the normal antibodies. And, even after a year, the vaccine recipients never developed a full immune reaction.
Insomnia, the most common sleeping disorder, is described by a person who can not produce sufficient sleep despite giving themselves sufficient sleep time.
While there are clinical definitions and guidelines for the diagnosis of insomnia, the author points out that if you loosened the guidelines, many more people would be categorized as insomniacs. For example, two out of three people reading this article will have trouble falling asleep at-least one night a week every week.
Common triggers of insomnia are emotional concerns and emotional distress (anxiety). Memory loops combined with emotional loops prevent the brain from shutting down. The author recommends those suffering from unwanted reoccurring thoughts when their head hits the pillow to develop a time for self-reflection that is before bedtime.
The most effective treatment for insomnia is CBT-1 (cognitive behavioral therapy). For more information on CBT-1 visit the National Sleep Foundations website.
Society and Sleep
The sleep aid industry generates 30 billion dollars a year.
In 65 separate studies of 4500 people, sleeping pills showed no benefit beyond placebo.
Sleeping pills like alcohol are sedatives, and they too work by sedating your cortex (higher brain). Sleeping pills are addictive, are connected to increased risk for cancer, decrease reaction time, promote grogginess and most importantly do not produce the same brain waves as natural sleep.
Caffeine and sleeping pills create a cycle of dependency and poor sleep. Sleeping pill leaves users feeling groggy in the morning, leading to more caffeine consumption, and caffeine consumption makes it harder to fall asleep, making users more likely to increase sleeping pill frequency and dose.
Many do not realize that sleeping pills are addictive and halting sleeping pill use will create withdraw induced insomnia.
Sleeping pills have only been shown to help patients fall asleep marginally faster, however sleeping pills will make you wake up the next day with fewer memories form the day before.
Statistically sleeping pill users are more likely to die and develop cancer than nonusers. Even occasional users (18 pills per year) were 3.6 times more likely to die. One reason for the increased risk of mortality is thought to be an increased risk of infection.
Sleep during childhood is critical to brain development. A child’s brain is under construction, and during mid-late childhood, a human brain will undergo its last bit of neural growth. Later, a child will experience a rise in deep NREM sleep and will begin the process of Aaptic pruning, which does not finish until after childhood. Synaptic pruning resultes in the brain’s maturation which starts in the back (visual and spatial regions) and ends in the frontal lobe (which is responsible for rational thought). Because the frontal lobe is underdeveloped, children and teens are often considered so irrational. Adults and children have very different brains. And, some have gone so far as to say children have an altered state of conscious experience.
Alarmingly, most children receive zero sleep education.
70% of parents believe their children get enough sleep when fewer than 25% of children (11-18 years old) get enough sleep. Data collected from 750,000 children show that they are sleeping 2 hours less than children 100 years ago. A century ago 95% of schools started at 9 AM, and 95% of children woke without an alarm.
Alarmingly, 80% of public high schools begin before 8:15 AM and 50% start before 7:20 AM. These early school start times deprive teens of much of their REM sleep.
Because of pubescent teen’s forward shifted (1-3 hours) circadian rhythm, waking up at 5:30 AM to a teen is like waking up at 3:30 AM for an adult.
During adolescence, while the brain is maturing, humans are at the most risk for developing a chronic mental illness. Researchers have found that if a subject does not obtain adequate REM sleep, they will exhibit symptoms identical to depression, anxiety, and schizophrenia. Early school times are depriving teens of much of their REM sleep and in turn, promotes an unstable mental state.
Researchers have found that no matter the age, the longer a child sleeps, the more intellectually gifted they were, and studies have also found that the amount of sleep time is correlated to school start time. Children who sleep more have higher IQs and better grades. Schools that accommodate teen’s forward shifted circadian rhythm have smarter and healthier students.
Identical twin research has shown that when one twin obtains less sleep than the other, the twin who slept more was superior intellectually, academically, had a more extensive vocabulary, and scored higher on reading and comprehension tests.
The township of Edina Minnesota shifted school start times from 7:25 to 8: 30 and their average verbal SAT score of 605 increased the following year to 761. Their Math SAT scores increased from 683 to 739. Several other counties who shifted there school start times forward saw student’s average GPAs rise the following year.
Reduced Teen Traffic Accidents
School districts in Minnesota after shifting school start time from 7:30 to 8:30 AM recorded a 60% reduction in traffic accidents of kids 16-18 years old. The advent of anti-lock brakes heralded as a revolution only reduced traffic accidents by 20-25%.
It Might Not be ADHD
From enforced wakening to sleep disorders, poor sleep often masquerades as ADHD. If you take a sleep-deprived child to the doctors, they will likely get diagnosed with ADHD.
Symptoms of sleep deprivation:
- Unable to maintain focus and attention deficient learning
- Behavioral difficulty
- Mental health instability
Symptoms of ADHD:
- Unable to maintain focus and attention deficient learning
- Behavioral difficulty
- Mental health instability
Recent surveys and clinical evaluations have shown that 50% of ADHD diagnoses actually have an undiagnosed sleep disorder like pediatric sleep-disordered breathing or obstructive sleep apnea. And, treatment of undiagnosed sleep disorders has shown to reverse ADHD symptoms.
A study of several large companies concluded that employee’s lack of sleep costs those companies an average of 54-million-dollars a year. Likewise, a lack of sleep costs the USA 411-billion-dollars per year. And, most industrialized nations lose 2% of there GDP per year due to lack of sleep.
Sleepy employees are:
- Less creative
- Less motivated
- Less happy
- More likely to commit ethically deviant behavior
Sleepy CEOs besides lacking in performance also affect the entire workforce, and this negative effect has been shown to last for days after.
One study found that employees who slept one hour more earned 4-5% more than their underslept counterparts. Consider that the average raise in the USA is 2.6%.
Proctor & Gamble and Goldman Sachs offer free sleep hygiene courses and have installed expensive light systems to help regulate their employee’s circadian rhythms. Nike and Google both have flexible the start and end times to accommodate differing chronotypes. NASA, now famous for its nap culture, first adopted napping after finding that short naps of 26 minutes offer a 34% increase in task performance and a 50% increase in alertness.
Make sure your doctor has slept for more than 7 hours. Medical errors are the third leading cause of death among Americans, and medical errors increase with lack of sleep
1 in 20 residents will kill a patient due to lack of sleep.
After a 30-hour shift, residents are 73% more likely to stab themselves with a needle or scalpel. Residents are 68% more likely to suffer a car accident after a long shift.
An attending physician who only gave themselves a sleep opportunity of 6 hours has a 170% increased risk for a serious surgical error.
More than 16 hours without sleep is dangerous for the patient and doctors.Studies have shown that reducing shifts to 16 hours reduced medical errors by 20% and made 400-600% fewer diagnostic errors.
After 22 hours without sleep, performance is impaired to the same degree as a legally drunk person. Would you let a drunk doctor operate on you?
I hope you have enjoyed this book summary of Why We Sleep by Matthew Walker PHD.
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