Why We Sleep: Unlocking the Power of Sleep and Dreams

Table of contents

1: To Sleep…
2: Caffeine, Jet Lag, and Melatonin: Losing and Gaining Control of Your Sleep Rhythm
3: Defining and Generating Sleep
4: Ape Beds, Dinosaurs, and Napping with Half a Brain: Who Sleeps, How Do We Sleep, and How Much?
5: Changes in Sleep Across the Life Span
6: Your Mother and Shakespeare Knew: The Benefits of Sleep for Your Brain
7: Too Extreme for the Guinness Book of World Records: Sleep Deprivation and the Brain
8: Cancer, Hear Attacks, and a Shorter Life: Sleep Deprivation and the Body
9: Routinely Psychotic: REM-Sleep Dreaming
10: Dreaming as Overnight Therapy
11: Dream Creativity and Dream Control
12: Things That Go Bump in the Night: Sleep Disorders and Death Caused by No Sleep
13: iPads, Factory Whistles, and Nightcaps: What’s Stopping You From Sleeping?
14: Hurting and Helping Your Sleep: Pills vs. Therapy
1. Cognitive Behavioral Therapy for Insomnia
15: Sleep and Society: What Medicine and Education Are Doing Wrong; What Google and NASA Are Doing Right
16: A New Vision for Sleep in the Twenty-First Century

1: To Sleep…

Two-thirds of adults throughout all developed nations fail to obtain the recommended eight hours of nightly sleep.
The shorter your sleep, the shorter your life span.
Human beings are the only species that will deliberately deprive themselves of sleep without legitimate gain.
The physical and mental impairments caused by one night of bad sleep dwarf those caused by an equivalent absence of food or exercise.
Sleep is the single most effective thing we can do to reset our brain and body health each day.

2: Caffeine, Jet Lag, and Melatonin: Losing and Gaining Control of Your Sleep Rhythm

Two factors that determine when we want to sleep and when we want to be awake.

The suprachiasmatic nucleus: An internal 24-hour clock located deep within your brain.
Adenosine: A chemical substance that builds up in your brain and creates a “sleep pressure.”

Got Rhythm?

All living things have a natural circadian rhythm that helps us keep time. We are not dependent on external cues, such as sunlight.
Humans circadian rhythm is actually slightly longer than 24 hours.
Core body temperature is one of those 24-hour rhythms governed by the suprachiasmatic nucleus.

My Rhythm Is Not Your Rhythm

40% of the population reaches peak wakefulness in the morning.
30% are more energized in the evening.
30% fall somewhere in between, with a slight leaning toward the evening.
An adult’s owlness or larkness, also known as their chronotype, is strongly determined by genetics.
Our society’s work schedule puts night owls at a disadvantage and favors those who are more energized in the morning.

Melatonin

The suprachiasmatic nucleus instructs the release of melatonin into the bloodstream after dusk.
Melatonin helps regulate the timing of when sleep occurs by systemically signaling darkness throughout the organism.
Melatonin has little influence on the generation of sleep itself.
Melatonin is not a powerful sleeping aid in and of itself.

Have Rhythm, Won’t Travel

Jet lag is caused by speeding through time zones without letting your biological clock catch up.
You feel tired and sleepy during the day, and unable to sleep solidly at night.
Melatonin can sometimes help trick your brain into believing it’s nighttime and help counteract the effects of jet lag.

Sleep Pressure and Caffeine

Adenosine is a chemical that builds up in your brain throughout the day. It increases your desired to sleep (sleep pressure).
Caffeine is the most widely used (and abused) psychoactive stimulant in the world.
Caffeine is the second most traded commodity on the planet, after oil.
Caffeine works by successfully battling with adenosine for the privilege of latching on to adenosine welcome sites—or receptors—in the brain.
By hijacking and occupying these receptors, caffeine blocks the sleepiness signal normally communicated to the brain by adenosine.

In Step, Out of Step

The two governing forces that regulate sleep—the 24-hour circadian rhythm of the suprachiasmatic nucleus and the sleep pressure signal of adenosine—are two distinct and separate systems. They are decoupled, but usually aligned.

Am I Getting Enough Sleep?

Two rules of thumb:

After waking up in the morning, could you fall back asleep at ten or eleven a.m.? If yes, then you’re probably not getting enough quality sleep.
Can you function optimally without caffeine before noon? If no, then you are most likely self-medicating your state of chronic sleep deprivation.

3: Defining and Generating Sleep

Self-Identifying Sleep

Sleeping organisms adopt a stereotypical position.
Sleeping organisms have lowered muscle tone.
Sleeping individuals show no overt displays of communication or responsivity.
Sleep is easily reversible, differentiating it from coma, anesthesia, hibernation, and death.
Sleep adheres to a reliable timed pattern across 24-hours.
The thalamus is the sensory gate of the brain. It puts up a perceptual barricade to block incoming sensory signals while you sleep.
You consciously lose track of time while you sleep.
But your subconscious brain is still capable of logging time with quite remarkable precision while asleep. Thus, why you sometimes wake up right before your alarm goes off.
When you dream, you maintain a sense of time, however, it is not particularly accurate. Often dream-time is prolonged relative to real time.

Two Types of Sleep

NREM = Non-rapid eye movement
- Four stages of increasing depth
REM = Rapid eye movement
- Brain activity almost identical to when we’re awake
- Associated with dreaming

The Sleep Cycle

NREM and REM stages play out in a recurring, push-pull battle for brain domination across the night in 90-minute intervals.
A key function of deep NREM sleep, which predominates early in the night, is to do the work of weeding out and removing unnecessary neural connections.
The dreaming stage of REM sleep, which prevails later in the night, plays a role in strengthening those connections.

How Your Brain Generates Sleep

Wakefulness is reception.
NREM sleep is reflection.
REM sleep is integration.

4: Ape Beds, Dinosaurs, and Napping with Half a Brain: Who Sleeps, How Do We Sleep, and How Much?

Who Sleeps

Sleep is universal. Without exception, every animal species studied to date sleeps, or engages in something remarkably like it.

One of These is Not Like the Other

Total amount of time is one of the most conspicuous differences in how organisms sleep.
Elephants sleep just 4 hours. Brown bats sleep 19 hours.
We don’t really know why it varies so much from one species to another.

To Dream Or Not To Dream

Not all species experience all stages of sleep.
All have measurable NREM sleep stages.
Insects, amphibians, fish, and most reptiles show no clear signs of REM sleep—the type associated with dreaming in humans.

If Only Humans Could

The way species sleep varies widely.
Cetaceans (such as dolphins and whales) and birds sleep with half a brain at a time.
REM sleep is strangely immune to being split across sides of the brain. Split brain sleeping only applies to NREM.

Under Pressure

Starvation will cause the search for food to supersede the need for sleep.
In flight, migrating birds will grab remarkably brief periods of sleep lasting only seconds in duration.

How Should We Sleep?

Hunter-gatherer tribes, such as the Gabra in northern Kenya or the San people in the Kalahari Desert, sleep in a biphasic pattern. Both these groups take a similarly longer sleep period at night (7-8 hours), followed by a 30-60 minute nap in the afternoon.
They go to sleep two to three hours after sunset, around 9 PM.
Midnight is supposed to be “mid-night.” Instead, for many of us, it’s usually the time when we consider checking our email one last time.
All humans, irrespective of culture or geographical location, have a genetically hardwired dip in alertness that occurs in the mid-afternoon hours.
When we are cleaved from the innate practice of biphasic sleep, our lives are shortened.

We Are Special

The total amount of time we spend asleep is markedly shorter than all other primates, yet we have a disproportionate amount of REM sleep, the stage in which we dream.
REM sleep exquisitely recalibrates and fine-tunes the emotional circuits of the human brain.
REM-sleep dreaming state fuels creativity.

5: Changes in Sleep Across the Life Span

Sleep Before Birth

-Prior to birth, a human infant will spend almost all of its time in a sleep-like state, much of which resembles the REM-sleep state. -Infants and young children who show signs of autism, or who are diagnosed with autism, do not have normal sleep patterns or amounts. Most notably is the shortage of REM—30-50% less than children without autism.

Childhood Sleep

Infants and young kids display polyphasic sleep: many short snippets of sleep through the day and night.
The master 24-hour clock that controls the circadian rhythm—the suprachiasmatic nucleus—takes considerable time to develop.

Sleep and Adolescence

During puberty, NREM sleep ramps up to prune brain connections with the goal of efficiency and effectiveness.
Deep sleep may be a driving force of brain maturation.
The circadian rhythm of adolescent teenagers shifts forward, so far that it passes the timing of their adult parents. So they want to stay up later.
Asking your teenager to go to bed and fall asleep at 10 PM is the circadian equivalent of asking you, their parent, to go to sleep at 7 or 8 PM.
Neither society nor our parental attitudes are well designed to appreciate or accept that teenagers need more sleep than adults, and that they are biologically wired to obtain that sleep at a different time than their parents.

Sleep in Midlife and Old Age

Sleep is more problematic and disordered in older adults.
Older adults need just as much sleep as they do in midlife, but are simply less able to generate that (still necessary) sleep.
REM sleep remains largely stable in midlife. But the decline of NREM sleep is already under way by your late twenties and early thirties.
The older we get, the more frequently we wake up throughout the night. The chief culprit is a weakened bladder.
The lower an older individual’s sleep efficiency score, the higher their mortality risk, the worse their physical health, the more likely they are to suffer from depression, the less energy they report, and the lower their cognitive function, typified by forgetfulness.

6: Your Mother and Shakespeare Knew: The Benefits of Sleep for Your Brain

Sleep-The-Night-Before Learning

Sleep restores the brain’s capacity for learning, making room for new memories.
The more sleep spindles an individual has at night, the greater the restoration of overnight learning ability come the next morning.

Sleep-The-Night-After Learning

Sleep is like clicking the “save” button. It protects newly acquired information against forgetting.
The slow brainwaves of deep NREM sleep serves as a courier service, transporting memory packets from a temporary storage hold (hippocampus) to a more secure, permanent home (the cortex).
Sleep clears out the cache of short-term memory for the new imprinting of facts, while accumulating an ever-updated catalog of past memories.
Sleep salvages memories that appeared to have been lost soon after learning.

Sleep to Forget?

Sleep discerns what memories to remember and which to forget.

Sleep for Other Types of Memory

Muscle memory is actually brain memory. Our brains remember how to do things.
Practice, followed by a night of sleep, makes perfect.
Daytime naps that contain sufficient numbers of sleep spindles also offer significant motor skill memory improvement, together with a restoring benefit on perceived energy and reduced muscle fatigue.
Sleep is an insurance policy against injury.

7: Too Extreme for the Guinness Book of World Records: Sleep Deprivation and the Brain

Vehicle accidents caused by drowsy driving exceed those caused by alcohol and drugs combined.
After being awake for nineteen hours, people who were sleep-deprived were as cognitively impaired as those who were legally drunk.
Students who stay up late cramming for tests experience a 40% deficit in their ability to make new memories relative to those that get a full nights sleep.
Wakefulness is low-level brain damage, while sleep is neurological sanitation.
Getting too little sleep across the adult life span will significantly raise your risk of developing Alzheimer’s disease.

8: Cancer, Hear Attacks, and a Shorter Life: Sleep Deprivation and the Body

Unhealthy sleep, unhealthy heart.
Adults 45+ who sleep <6 hours are 200% more likely to have a heart attack or stroke compared to those sleeping 7-8 hours.
In the Northern Hemisphere, the switch to daylight savings time in March results in most people losing an hour of sleep opportunity. When viewed across the millions of daily hospital records, this seemingly trivial sleep reduction comes with a frightening spike in heart attacks the following day.
The less you sleep, the more you are likely to eat.
Chronic sleep deprivation is one of the major contributors to type 2 diabetes.
Insufficient sleep is linked to obesity.
Short sleep causes the body to deplete muscle mass and retain fat.
Men who suffer from sleep disorders (sleep apnea and snoring) have significantly lower levels of testosterone.
Your immune response suffers after a single night of reduced sleep.

9: Routinely Psychotic: REM-Sleep Dreaming

REM sleep accounts for the hallucinogenic, emotional , and bizarre experiences with a rich narrative.
REM sleep is a state characterized by strong activation in visual, motor, emotional, and autobiographical memory regions of the brain, yet a relative deactivation in regions that control rational thought.
MRI scans be used to predict with significant accuracy the content of your dreams by matching images of brain activity to baseline templates.
Dreams are not a wholesale replay of our waking lives.
Daytime emotions, however, do have some influence over the emotional themes of our dreams.

10: Dreaming as Overnight Therapy

REM sleep helps us divorce emotion from experience. We can therefore learn and usefully recall salient life events without being crippled by the emotional baggage that those painful experiences originally carried.
Dreaming about difficult life events helps people gain clinical resolution from their despair.
Like a master piano tuner, REM sleep readjusts the brain’s emotional instrument at night to pitch-perfect precision.

11: Dream Creativity and Dream Control

Sleep builds connections between distantly related informational elements that are not obvious in the light of waking day.
Relational memory processing receives an accelerated boost from REM sleep.
Like an insightful interviewer, dreaming takes the approach of interrogating our recent autobiographical experience and skillfully positioning it within the context of past experiences and accomplishments, building a rich tapestry of meaning.
Lucid dreaming is possible. Some people can control when and what they dream while they are dreaming.

12: Things That Go Bump in the Night: Sleep Disorders and Death Caused by No Sleep

Somnambulism

Sleep disorders that involve movement:

Sleepwalking
Sleep talking
Sleep eating
Sleep sex
Sleep homicide (very rare, but it has happened)

Insomnia

Clinical difficulty falling asleep or staying asleep. Widespread problem. Approx. 1/9 Americans, or 40 million suffer. Often triggered by worry or anxiety.

Narcolepsy

A neurological disorder with three core symptoms. Excessive daytime sleepiness = Sudden, irresistible urges to sleep Sleep paralysis = Loss of ability to talk or move when waking up from sleep. Cataplexy = Sudden loss of muscle control. Caused by body paralysis of REM sleep without the sleep of the REM state itself.

Fatal Familial Insomnia

Genetically inherited disorder causing a complete inability to sleep and resulting in death. Mutated prion proteins attack the thalamus and render it incapable of blocking senses from the outside world.

Sleep Deprivation Experiments with Rats

Rats will die after 15 days without sleep, on average. Cause of death was a simple bacteria infection from their gut. Under normal circumstances, it would be easily quelled by a rested, healthy immune system.

13: iPads, Factory Whistles, and Nightcaps: What’s Stopping You From Sleeping?

Constant electric light
Alcohol
Regularized temperature
Caffeine (Chapter 2)
A legacy of punching time cards

Modern Light

Artificial evening light will fool your suprachiasmatic nucleus into believing the sun has not yet set.
Melatonin is not released on schedule.
Evening blue LED light has twice the harmful impact on nighttime melatonin suppression than warm, yellow light from old incandescent bulbs.
Maintaining complete darkness throughout the night is equally critical.

Alcohol

Alcohol fragments sleep, therefore sleep is not continuous and not restorative.
Alcohol is a powerful REM suppressor, depriving you of dream sleep.

Temperature

Core body temp must decrease 2-3 degrees Fahrenheit to initiate sleep.
65 degrees is ideal.
Body temp is controlled by your hands, feet, and head. Warm these areas to draw out heat trapped in the body’s core.

Industry

The affects of being artificially wrenched from sleep (alarm clocks) include a spike in blood pressure and a shock acceleration in heart rate caused by an explosive burst of activity from the flight-or-flight branch of the nervous system.
Don’t press snooze and afflict yourself to this more than once.

14: Hurting and Helping Your Sleep: Pills vs. Therapy

Sleep pills almost always do more harm than good.
The quality of pill-induced sleep is deficient.
Sleep pills are addictive.
Individuals using prescription sleep medications are significantly more likely to die and to develop cancer than those who do not.

Cognitive Behavioral Therapy for Insomnia

Techniques intended to break bad sleep habits and address anxieties that inhibit sleep:

Establish a regular bedtime and wake-up time, even on weekends.
Go to bed only when sleepy and avoid sleeping on the couch early/mid-evenings.
Never lie awake in bed for a significant period of time.
Avoid daytime napping.
Reduce anxiety-provoking thoughts and worries.
Remove visible clock faces from view in the bedroom.

15: Sleep and Society: What Medicine and Education Are Doing Wrong; What Google and NASA Are Doing Right

The World Health Organization recognizes lack of sleep as a global health epidemic.
The brain can never recover all the sleep it has been deprived of. We cannot accumulate a sleep debt throughout the week and catch up on the weekends.

Business

Routinely, business leaders mistakenly believe that time on-task equates with task completion and productivity.
A study across four large US companies found that insufficient sleep cost almost $2,000 per employee per year in lost productivity.
Insufficient sleep robs most nations of more than 2 percent of their GDP.
Creativity, intelligence, motivation, effort, efficiency, effectiveness when working in groups, as well as emotional stability, sociability, and honesty. All of these things are systematically dismantled by insufficient sleep.
Sleep-deprived individuals also generate fewer and less accurate solutions to work-relevant problems they are challenged with.
People are much more likely to lie, cheat, steal, and blame others for their mistakes when then sleep six or less hours.

Inhumane Use of Sleep Loss

Sleep deprivation is a form of torture.
Very ineffective for gathering accurate information.
Causes permanent physical and mental harm.

Education

Teenagers in America routinely wake up at 5:30, or earlier, to get to class—this is crazy.
Adolescence is the most susceptible phase of life for developing chronic mental illnesses, such as depression, anxiety, schizophrenia, and suicidality. Sleep deprivation can be the tipping point between psychological wellness and lifelong psychiatric illness.
Increasing sleep by way of delayed school start times wonderfully increases class attendance, reduces behavioral and psychological problems, and decreases substance and alcohol use.
It’s estimated that more than 50% of all children with an ADHD diagnosis actually have a sleep disorder.

Healthcare

Throughout the course of their residency, one in five medical residents will make a sleepless-related medical error that causes significant, liable harm to a patient.
One in twenty will kill a patient due to a lack of sleep.
Medical errors are the third-leading cause of death among Americans after heart attacks and cancer. Sleeplessness undoubtedly plays a role in those lives lost.
If you are about to undergo an elective surgery, you should ask how much sleep your doctor as had.
One cannot “learn” how to overcome a lack of sleep and develop resilience.

16: A New Vision for Sleep in the Twenty-First Century

Link individual sleep trackers with connected devices like thermostats and lighting.
We need to increase sleep awareness and teach it in our schools.
Companies could incentivize their employees to get better sleep.
Business should offer more flexibility with their work hours. Allowing larks to start early and owls to stay late.
Health insurance costs could go down if people were rewarded to prioritize sleep.