Why We Sleep: Unlocking the Power of Sleep and Dreams


Why We Sleep: Unlocking the Power of Sleep and Dreams
Category: Medicine
Publisher: Scribner
Published: 10/3/2017
Sleep is one of the most important aspects of our life, health and longevity and yet it is increasingly neglected in twenty-first-century society, with devastating consequences: every major disease in the developed world - Alzheimer's, cancer, obesity, diabetes - has very strong causal links to deficient sleep.

Book Summary - Why We Sleep: Unlocking the Power of Sleep and Dreams by Matthew Walker

Key Insights

We sleep because we need it to survive. Sleep is the time that we rest, regroup, and re-energize ourselves. Getting enough sleep is critical for your physical and mental health.

Sleep is important for your mental functions. Your brain uses the time to process emotional experiences and organize your memories. If you don’t sleep enough, you’ll feel the cognitive impairment.

More than just slowing down, sleep is a matter of life and death. Chronic sleep deprivation is linked to a variety of serious health issues. Also, in a state of sleep deprivation, you’re like a drunk. So you could pose a danger to others, especially behind the wheel of a car.

Sleep is something all animals do in some form. For humans, the unique aspect is the amount of time spent dreaming. Dreams hold ideas and problem-solving that can be inspirational if you’re able to identify them.

But first, you need to sleep enough to harness the full power of your slumber.

Key Points

Your circadian rhythm is your body’s internal clock.

Are you a morning person or a night owl? Maybe you like to stay up late and get your best work done in the middle of the night. These preferences are determined by your circadian rhythm.

The circadian rhythm is like a clock inside your body. During every 24-hour period, there are times where you feel the need to sleep or times when you feel more awake. Your circadian rhythm also gives you other biological cues, like being hungry or thirsty. Some fluctuations in your mood can also be linked to your circadian rhythm.

If you weren’t waking up to an alarm clock or dictating your day based on a work schedule, your circadian rhythm would drive when you do your daily activities. Each person’s body clock is a little different. But you can get a sense of it based on when you naturally feel sleepy or when you wake up when you haven’t set an alarm.

If you’re a night owl, your morning meetings are probably harder. Most people do better during the day, but 30 percent of people are closer to nocturnal. For these folks, morning and afternoon are when they’re in their sleepier phases. It’s harder for them to get enough sleep.

You dream and maybe even sleepwalk during your REM phase of sleep.

Sleep has three phases: light, deep, and REM. Rapid-eye-movement (REM) sleep is named for the way that your eyes move from side-to-side under your eyelids while you’re in the REM phase of sleep. Light and deep sleep are both non-REM sleep.

You go through the phases of sleep in cycles. Starting with light, then deep, then REM. Then, you start the cycle over. The amount of time spent in each phase varies by cycle. The earlier cycles will have more time in deep sleep and the later cycles will have more time in REM.

Each phase has a purpose and your brain activity is different in each phase. Think of your brain as a computer. When you start sleeping, you’re disconnecting your computer from inputs (like typing on the keyboard). Deep sleep allows you to organize the files in your mind, like defragmenting a computer. Some temporary files are deleted and the important ones are stored together.

REM sleep differentiates you from a computer. During REM sleep, you’re basically just having random thoughts that may or may not be related to other things going on. If something useful comes out of this, you may remember it. This is why dreams happen during REM sleep.

Every animal sleeps but different types and amount of sleep.

For all animals on this planet, sleep is a part of life. But the way you sleep is very different from the way other animals sleep. Each creature needs sleep but has adapted the way it sleeps.

The amount of the day that is spent sleeping varies among animals. You probably know that you’re supposed to get around eight hours of sleep per day. But elephants only need about four. On the other end of the spectrum, the brown bat sleeps for about 19 hours of every day.

It’s unclear why certain animals sleep for more and others for less. There are no clear themes that explain the differences. Even within the same type of animal, there can be huge variations. For example, two animals within the order Rodentia have a difference of about 7 hours of sleep on average.

The type of sleep is also different, often by necessity. There are some birds that are able to sleep while flying. As another example, sharks have no eyelids but they still sleep. Their eyes are open during their shut-eye, but scientists have discovered that they do sleep.

One commonality found in sleep patterns is the presence of REM sleep. Only mammals and birds have REM sleep. The exceptions are aquatic mammals. This is probably because REM sleep comes with paralysis that would cause the water mammals to drown.

Humans dream a lot compared to other mammals. Those dreams can give you great ideas or inspiration.

Dreams happen during REM sleep, which means that all mammals dream. But there are variations in dreams just like sleep. For example, a dog dreams about 10 percent of the time it sleeps. In contrast, humans dream up to a quarter of the time they sleep.

There are evolutionary theories for why humans can dream more. With fire, humans could sleep without fear of predators. So, they spend more time in the paralysis state of REM sleep. This extra dream time is thought to be part of the emotional, social, and cognitive development that has come since that time for humans.

Dreams are a valuable part of your mental processing. Scientists have been able to use brain activity to identify what people are dreaming about. Depending on what part of the brain is active, it means different things. You mostly dream about recent events that are emotional. Reviewing it in a dream is less stressful. You can process it and move forward.

Creative inspiration can also come during your dream state. You can see connections that you couldn’t see during your awake state. Great ideas can come with this enhanced problem-solving ability. People like Thomas Edison and Salvador Dali would use their REM sleep for inspiration.

You can do what Dali did. Fall asleep holding a key above a plate. When you enter REM, your muscles relax and you drop the key into the plate. You’ll awaken while you can still remember what you were seeing in your REM state. Use it to inspire your creativity.

Sleep deprivation is dangerous for you and, possibly, others.

At a minimum, not getting enough sleep slows you down. You don’t process information as well as you would if you were well-rested. But sleep is also critical for memory and chronic sleep deprivation is linked to Alzheimer’s.

If you suffer from heart disease or high blood pressure, it’s likely your doctor has recommended at least two of three things. They probably told you to exercise, eat better, and sleep more.

The first two probably seem obvious, but getting a full night’s sleep can mean the difference between a healthier lifestyle and an increased risk of fatal illness. Simply by sleeping more you can lower your blood pressure. This reduces your risk of cardiovascular disease by as much as 45 percent.

Chronic sleep deprivation leads to a number of health problems. This is because your body’s immune system needs sleep to work properly. You can experience negative effects on your health ranging from weight gain to pre-diabetic symptoms.

Even if you realize that sleep deprivation is bad for you, you might not know that your lack of sleep can endanger others. Sleep deprivation impacts your levels of concentration and impairs your judgment.

To put it another way, driving a car when you haven’t slept enough can be as bad as driving a car drunk. Your impaired functioning leads to dangerous situations that put you and other people at risk.

When you sleep less than the recommended seven hours your body also tries to compensate. One way that it does that is through microsleeps. A microsleep is just like regular sleep. The only difference between microsleep and full sleep is the length of rest. The effect on your body is the same.

A microsleep may only last a few seconds but during that time you have no control of your faculties. Imagine if you’re driving on a busy road and a car in front stops during those few seconds of microsleep. The results could be devastating.

Your brain is affected by sleep disorders.

Sometimes trying to get enough sleep is easier said than done, particularly if you suffer from a sleep disorder. There are numerous sleep disorders and they vary in severity. But they all disrupt your sleep patterns in some way.

Sleep disorders can have debilitating effects on your physical and mental health. Serious cases of insomnia can cause infections and a depressed immune system due to sleep deprivation. A lack of sleep can also seriously disrupt normal brain activity.

If you sleepwalk, a disruption in brain activity is likely the cause. The brain prevents you from entering the REM stage of sleep where dreaming occurs. This issue often results in sleepwalking, a condition that might endanger your life.

Although most cases of sleepwalking are relatively non-eventful, it can be dangerous in extreme cases. Imagine waking up to find yourself sitting in your car or worse still, waking up while you are still driving. In one particularly alarming case in 1987, a man stabbed his mother-in-law to death after driving 14 miles to her home in a sleepwalking state.

Sleep disorders can be disruptive both physically and mentally. They should be taken seriously before they turn tragic for you or others.

Caffeine, alcohol, and nicotine are bad for sleep. Getting sunlight is good for sleep.

Sleep has a hormonal component. Throughout your waking hours, your brain builds up its store of adenosine. As you have more adenosine, you start to feel sleepy.

Caffeine can help you feel more alert, but it’s only a temporary solution. You don’t feel the effects of adenosine, but you still produce it. As the caffeine wears off, you feel even more fatigued. And if you’re blocking your ability to respond to adenosine, you’re not going to get the sleep that your body needs.

An after-dinner drink may be a common ritual for some, but alcohol is bad for the quality of your sleep. It may help you relax, but it actually keeps you from entering deep sleep. A lot of alcohol can also make it harder to breathe while you sleep. Also, when the effects wear off, you’ll probably wake up.

Nicotine is another problematic substance. People who smoke probably find it to be relaxing. But nicotine is a stimulant so you’re not going to get past the light sleep phase. What’s worse is that nicotine is addicting. By the morning, your body is feeling withdrawal and you wake up early to satisfy the craving.

Fortunately, there are some ways to get better sleep. You can take a hot bath before bed. You relax in the heat and then as you cool down after, you feel drowsy.

All the modern technology you have is convenient, but it also messes with your sleep. Limit your artificial light and screen time before bed. And getting enough natural sunlight during the day will help regulate your sleep cycle. You can even start relying on natural light to wake you up in the morning after a full night’s rest.

The Main Take-away

Every animal on Earth sleeps. Humans go even further, using sleep for inspirational dreams, emotional processing, and memory development. Since humans discovered fire, sleep has played a unique role for our species.

Without enough sleep, you may struggle with high blood pressure, weight gain, diabetes, Alzheimer’s, and cardiovascular issues in the long-term. You may also feel foggy or emotional in the short-term.

Your body may compensate for sleep deprivation with microsleeps. By sleeping in a tiny increment, your body goes through the motion of sleep. This can put you in a dangerous position if you’re doing something like driving. It can also put you in an embarrassing position if it happens during a meeting.

If you want to prioritize sleep, be careful about what you put in your body. Ease up on caffeine and don’t rely on alcohol to get sleepy. Try to quit that nicotine habit and get lots of natural sunlight during the day. Your body’s internal clock wants you to get enough rest, so it’s better to just go with the flow.

About the Author

Matthew Walker calls himself the “Sleep Diplomat.” He has built a career in studying the science of sleep and its impacts.

Walker was born in the United Kingdom. He studied neuroscience at the University of Nottingham and got his Ph.D. in neurophysiology from Newcastle University.

While working as a professor of psychiatry at Harvard Medical School, Walker studied the effects of sleep on performance. He then moved to a role at the University of California, Berkeley. There, he created the Center for Human Sleep Science to further research sleep.

Walker has also worked with technology companies. With the life sciences division of Google, he helped to develop a sleep diary. Walker also worked with Hello on a sleep tracking device until the company ceased operations in 2017.

Why We Sleep is Walker’s first book.

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