Book Review: Why We Sleep

My last book in 2019, that I squeaked through to a finish on Dec 30th, was Matt Walker's,  Why We Sleep: Unlocking the Power of Sleep and Dreams.  Matt Walker is Professor of Neuroscience and Psychology at the University of California, Berkeley, and Founder and Director of the Center for Human Sleep Science.  I had originally heard the author's 15-minute Ted Talk titled, Sleep Is Your Superpower and was quite intrigued by what he had to say.

AARP has an initiative called The Global Council on Brain Health which has five pillars which include: Move, Discover, Relax, Nourish, and Connect.  Sleep is identified as one of the main drivers of Brain Health in this context and they have an entire report called the Brain-Sleep Connection. 

For the purposes of this book review, I have tried to identify the 10 key Learnings from Matt Walker's book.  These might not be the ones the author might pick or a scientist might pick.  I have selected these because they struck me as quite insightful and ones that I am likely to remember as I move on to other interesting books in 2020 and beyond!

Also, my perspective is that of a lay reader (in the finance field, no less) - so any scientific debate regarding these insights is for the experts to settle!

Top 10 learnings from Matt Walker's Book, Why We Sleep:

10.  Melatonin provides the official starting signal for sleep to start.

As a heavy traveler for both business and pleasure that has taken me around the globe for over 30 years, I have always wondered about what Melatonin actually does; but never have tried it myself.  This insight that melatonin is a starting signal was very useful.

iPads: Sleep research shows that compared to reading a printed book, reading on an iPad suppresses melatonin release by over 50 percent at night. iPad reading delayed the rise of melatonin by up to three hours, relative to the natural rise in these same individuals when reading a printed book.

In experiments, when reading on the iPad, instruction to sleep did not occur until the early-morning hours, rather than before midnight. Thus individuals took longer to fall asleep after iPad reading relative to reading paper editions.

Alarm Clocks: The alarm clock jangles the nervous system to waking up and gets it into a fight or flight mode.  A bad way to wake one's system up, it turns out.  And the snooze button repeatedly does this to detrimental health effects.

I shared this with my son Rahul, a sophomore in college. We were out skiing over the holidays at this time.   I got up early in the morning to get ready for skiing, and without missing a beat, in the middle of his sleep he quipped, "Dad, you are getting my flight or fight response going..!"  

Then he rolled over in his bed and went back to sleep.

9.  Caffeine has an average half-life of five to seven hours. 

The half life of caffeine and its effects is an interesting concept (just like nuclear half life that we know in popular culture).  We learn that 50% of the effect of coffee is left in your system approximately 6 hours after we drink it.  And 25% 12 hours later.

The author shares experiments by NASA scientists who found that spiders exposed different drugs included LSD, speed (amphetamine), marijuana, and caffeine had the worst impact on their spider web building with caffeine.

From the book:  Impact of Caffeine on spider web creation

8.  Recovering one's sleep is not a thing!

According to the author, regardless of the amount of recovery opportunity, the brain never comes close to getting back all the sleep it has lost. That humans can never “sleep back” that which we have previously lost is perhaps my key learning from this book.

In an experiment subjects were tested whether their functioning could return to optimal after lack of sleep with later recovery.  Even after three nights of ad lib recovery sleep, their performance did not return to that observed at the original baseline assessment when those same individuals had been getting a full eight hours of sleep regularly.

Matt Walker has this to say about people who claim they can get by with less than 7-8 hours of sleep: "Sixty years of scientific research prevent me from accepting anyone who tells me that he or she can “get by on just four or five hours of sleep a night just fine.”

So much for cities that never sleep and pulling all-nighters!

7.  Impact of lack of sleep

According to the author, we are physically and emotionally dependent upon sleep.

Insufficient sleep apparently causes telomeres at the end of one's chromosomes become damaged, making one's DNA spirals become exposed and your now vulnerable genetic code cannot operate properly, like a fraying shoelace without a tip.  I love the shoelace-cap metaphor that the author uses - easy to understand and remember! Thus lack of sleep can lead to detrimental health effects.

On the topic of Alzheimer's disease in particular,  Matt Walker says that sleep disturbance precedes the onset of Alzheimer’s disease by several years, suggesting that it may be an early-warning sign of the condition, or even a contributor to it.

I serve on the Board of the Alzheimer's Association in New England and am thus interested in this subject.  I found the extensive treatment that Matt Walker gives to Alzherimer's Disease in his book full of fresh insights.

6.  We sleep in 90-minute cycles that include the so-called NREM and REM Sleep.

NREM sleep or deep sleep which predominates early in the night does the work of weeding out and removing unnecessary neural connections.

REM Sleep or the dreaming stage of sleep, which comes into play later in the sleep cycle, plays a role in strengthening neural connections.

Share of REM / NREM sleep:
- For a 6-month old infant it is:  50% each share between NREM and REM sleep.
- For a 5-year old it is a 70 - 30 share between NREM and REM sleep.
- For late teens it is 80 - 20 NREM vs REM sleep and remains so to mid-adulthood.  

Sleep Efficiency: As we age, there is fragmentation, that is we wake up throughout the night. There are many causes, including interacting medications and diseases, and also a weakened bladder.

5.  NREM: For long-term memories

Each night, during the NREM deep sleep, the brain will move memories of recent experiences from a short-term storage site to a long-term storage location.  Thus, if we don't accrue deep sleep, we are not forming long term memories!

A region of the brain called the hippocampus helps store the information collected during the day. But it has a limited storage capacity.  Deep sleep clears out the hippocampus, replenishing this short-term information repository with plentiful free space.

So if we don't experience deep sleep, we have not given a chance for the memories to be trasnferred to long term storage; rather the next day the hippocampus is over-written with the next day's new experiences.

Matt Walker reminds us of Simon and Garfunkel's song The Sounds of Silence.  This one of my favorite songs for sure! The author explains that the song describes greeting their old friend, darkness (sleep). And the relaying of the day’s waking events to the sleeping brain at night in the form of a vision, softly creeping. Finally how those fragile seeds of waking experience, sown during the day, have now been in the brain during sleep.


Simon & Garfunkel, brain science pioneers - just sayin' ...!

4.  REM: Dreaming can soothe painful memories and inspire creativity.

There have been all kinds of symbolic interpretations of dreams in popular culture, that are frankly hard to shake.  The book with its abundant explanation of scientific experiments convincingly resets the understanding of dreaming as a biological function with attendant benefits.  Along the way, in an extensive section of the book the author (and current neuroscience) demolishes Freudian Psycho-analysis (sigh!).

Examples abound of aha moments during sleep.  They include Mendelev and the Periodic Table, Paul McCartney and the song Let it Be, Otto Loewi and neurotransmitters, Edison and his inventions and Shelley and Frankenstein.

Autism and REM Sleep: Autistic individuals show a 30 to 50 percent deficit in the amount of REM sleep they obtain, relative to children without autism.  This is more of a correlation than a causation perhaps - but what a correlation!

3.  Practice plus Sleep makes perfect 

The brain continues to improve skill memories in the absence of further practice. This learning occurs exclusively across a period of sleep, and not across equivalent time periods spent awake.  Practice does not make perfect. It is practice, followed by a night of sleep, that leads to perfection.

The author jokes, if you don’t snooze, you lose.

2.  Micro-sleep

During a micro-sleep, the brain becomes blind to the outside world for a brief moment, that is for 1-2 seconds.  Control of our motor actions, such as those necessary for operating a steering wheel or a brake pedal, will momentarily cease during micro-sleep.

As a result, two seconds of micro-sleep at 30 mph can result in the vehicle changing lanes (perhaps onto oncoming traffic).

Getting behind the wheel of a car when having slept just four hours or less the night before and the chances of being involved in a car accident are 11.5 times higher.  One can imagine the harmful effects of micro-sleep on professions such as truck driving.

1.  Good sleeping Habits

There is a very useful appendix to the book where the author gives 12 tips for healthy sleep including: gaining daily sunlight exposure, developing asleep schedule, not too late with eating, exercise or naps, avoiding alcohol, caffeine & medications (if possible)

And .... (ahem, note to self) no iPads before sleep!

In Conclusion ....

Why We Sleep is a well written, accessible and timely book that I recommend just to get a handle on how sleep works and its importance.

Without sleepwalking, I suggest you that you might get this book!