• Dan Connors

Why do we sleep? What does a good night's sleep do for our brains, bodies, and spirits?

Updated: Jun 14, 2020


Why We Sleep: Unlocking the Power of Sleep and Dreams, by Matthew Walker 2017


FIve of five stars *****


Matthew Walker, director of UC Berkeley's Sleep and Neuroimaging Lab, wrote what I found to be the definitive book on sleep, telling the story of why we need sleep, what it does for our brain and body, and what happens if we don't get enough. He uses numerous studies that were performed on subjects who had sleep or were sleep deprived, and the results are convincing and shocking in some cases.

In some ways this book is a cry for Americans to get more sleep. The average amounts of slumber have been trending down and are now below 7 hours per night, with some getting much less. (30% of Americans get less than 6 hours a night) Most experts recommend 7 to 9 hours of quality sleep for adults, with 8 hours being the preferred mean. Many things in our culture minimize the importance of sleep, and with the advent of caffeine and artificial light we push ourselves beyond our body's needs. Employers and schools in some cases encourage people to skimp on sleep and make fun of those don't.


All animals, including humans, need to sleep. In evolutionary terms this seems like it would be a big risk, since during sleep all creatures are vulnerable to predators and unable to sense their environment. Elephants sleep only 4 hours and Lions 15, while most primates average 10-15 hours. Even marine mammals like dolphins have evolved a way to sleep while not dying. by sleeping in only half of their brain at a time. Sleep is a universal need and activity in the wild, as it is with us.


Walker details how the sleep cycle is governed by two critical factors. First, there is the circadian rhythm that is our internal biological clock. It tells us when to be tired and when to wake up, and can vary between night owls and morning larks. The circadian clock also causes an afternoon drop in energy that causes us to feel tired after lunch. The second factor is sleep pressure, which is caused by a chemical called adenosine that gradually rises in your body while you are awake and is flushed out when you go to sleep. If you've ever stayed up past midnight you've felt this pressure to go to sleep and it is overpowering unless counteracted temporarily with caffeine.


Our sleep cycle is dominated by two types of sleep as documented in sleep studies. The first, REM sleep, is when we are dreaming and our mind is actively working. REM stands for Rapid Eye Movement, because our eyes move beneath the eyelids during this type of sleep, while the rest of our body is paralyzed. The second mode of sleep, when the eyes don't move, is a deeper sleep called NREM sleep. Here the brain waves slow down, there is no dreaming, and processes take place to weed out unimportant events of the day. Walker shows that the first half of sleep is dominated by NREM sleep while the few hours before we wake up are dominated by dreaming, or REM, sleep. Each type has an important function that needs to happen for the sleep to do its job. Thanks to the alarm clock, it's REM sleep that is lost most often, and there can be serious consequences to the brain over time for this.


While infants can sleep for up to 14 hours a day, Walker singles out teens and senior citizens as the groups with the most sleep problems. Teens experience a shift in their circadian clock with puberty and naturally want to stay up later. Unfortunately, with most high schools starting classes before 8 AM, requiring a 6 AM wake up time, teens are chronically sleep deprived, trying to catch up on weekends- which studies show never works. Sleep deficits in adolescence hurts concentration in school and basic functioning like driving cars or playing in sports. Unfortunately, teens are often unaware that they are sleep deprived, and school administrators are resistant to making changes because of school bus schedules and other factors.


Senior citizens, according to studies, suffer from a declining quality of sleep as they age. The need for 8 hours of sleep is the same, but the aging process lowers the efficiency of the brain waves during sleep while increasing disruptions from bladder and other organs that can wake Seniors up multiple times per night. There are links between poor quality sleep and Alzheimer's disease, though it's unclear whether one causes the other or vice versa, but research into improving the sleep of seniors is ongoing.


Why do we sleep? Because if we don't - we die. Walker details a case where a man was totally unable to sleep for weeks and no doctors or medicines were able to help. In a matter of weeks he deteriorated rapidly and died. Sleep not only restores the body, it provides critical help to the the systems that control learning, concentration, blood pressure, emotional health, creativity, weight control, and the immune system. Walker details the following problems that can come from lack of sleep:


  • There are links between lack of REM sleep and Autism.

  • People with dementia and Alzheimer's disease have difficulty sleeping.

  • After 16 hours of being awake, most people's cognition begins to fail, after 19 hours they are as impaired as someone legally drunk. Over a million auto accidents a year are caused by microsleeps that overcome drivers and shut down their senses for critical seconds.

  • Sleep deprivation is linked to emotional irrationality as the amygdala enlarges.

  • Insufficient sleep is linked to high blood pressure and elevation of the fight-or-flight sympathetic nervous system. This leads to chronic inflammation, heart disease and other circulatory problems. (There are more heart attacks around daylight saving's times every year)

  • One study showed that volunteers who were sleep deprived were much less resistant to viruses that those with a good night's sleep.

  • There's been shown a higher level of cancer onset among shift workers who's sleep cycle is disrupted, and natural killer cells that fight cancer are less prevalent in those with only 4 hours of sleep a night.

The values of dreaming and REM sleep have been detailed in many books, but I wasn't aware that this type of sleep had so much value. REM dreaming has been used to help PTSD patients remove the emotional charge around past events, as a proper rehashing in dreams can look at the causes without as much emotional charge. Emotional intelligence rises in patients with dream sleep. Creativity also rises during dream sleep, as the brain establishes many new connections for things learned during the day. Things that have been discovered during dreams include the periodic table, Google, DNA, the theory of Relativity, the Beatle's song "Yesterday", and the Terminator movies. During sleep we are able to make unique connections that we simply cannot while awake.


This book was a revelation to me, as I've always taken sleep for granted. Professor Walker details in convincing fashion why we need sleep and what happens when we don't get it, which is often. Doctors and medical articles rarely focus on how much sleep we are getting, and with our overloaded lives it's tempting to cut off an hour or two here or there. While an occasional short night won't have as much effect, the research shows that a large number of these sleep-shortened nights could have a devastating affect to our mental and physical health.


In addition, the author presents plenty of tips for getting a good night's sleep, and advises people to stay far away from sleep drugs like Ambien and Lunesta, which don't work much better than a placebo and cause sleep to be of lower quality. Instead of drugs, research points to cognitive behavioral therapy, (CBT) as a better and safer aid to insomniacs. At the end of the book, he presents these tips for better sleep:


Twelve Tips for Healthy Sleep from NIH Medline Plus

1- Stick to a sleep schedule- go to bed and wake up at the same time every day.

2- Don't exercise late in the day (3 hours or less before bedtime)- it interferes with the onset of sleep

3- Avoid caffeine and nicotine from late afternoon onward.

4- Avoid alcohol before bedtime- it robs you of REM sleep.

5- Avoid large meals or snacks late at night.

6- Avoid medicines that delay or disrupt your sleep.

7- Don't take naps after 3 PM- makes it harder to fall asleep at night.

8- Relax before bed

9- Take a hot bath before bed- drop in body temperature helps with sleep.

10- Make your bedroom, cool, dark, and gadget-free. Blue light from computers and phones are especially disruptive.

11- Get outside in natural sunlight at least 30 minutes every day.

12- Don't lie in bed awake. If more than 20 minutes without sleeping, get up and do something relaxing until you feel more tired.




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