Why We Sleep: Unlocking the Power of Sleep and Dreams by Matthew Walker
I personally have a large appetite for sleep science. It is fascinating to learn about how key this often overlooked part of our day relates to optimal health.
Many people assume that our circadian rhythm is driven primarily by the day/night cycle of the sun and it’s associated light/dark periods. Early in the book, the author highlights work done much earlier to show that humans, like plants, have their own endogenous circadian rhythms (separate from the light influence) and that they are slightly longer than 24 hours. To me, right away, this highlighted this contributes to the bodily stress of varying from this rhythm in terms of our daily activities.
These rhythms are also different in people in relation to the time of day they start. Early risers make up about 40% of the population whereas other evening types make up 30%. The remaining are somewhere in the middle. Further, these types are hardwired genetically in the DNA.
Many people have taken melatonin to help with sleep onset, but it doesn’t actually generate sleep:
melatonin helps regulate the timing of when sleep occurs by systemically signaling darkness throughout the organism. But melatonin has little influence on the generation of sleep itself: a mistaken assumption that many people hold. To make clear this distinction, think of sleep as the Olympic 100-meter race. Melatonin is the voice of the timing official that says “Runners, on your mark,” and then fires the starting pistol that triggers the race. That timing official (melatonin) governs when the race (sleep) begins, but does not participate in the race. In this analogy, the sprinters themselves are other brain regions and processes that actively generate sleep. Melatonin corrals these sleep-generating regions of the brain to the starting line of bedtime. Melatonin simply provides the official instruction to commence the event of sleep, but does not participate in the sleep race itself.
A very useful understanding of jet lag was addressed in this section of the book as well. First, was that the suprachiasmatic nucleus (SCN) can only
West or east, jet lag still places a torturous physiological strain on the brain, and a deep biological stress upon the cells, organs, and major systems of the body. And there are consequences. Scientists have studied airplane cabin crews who frequently fly on long-haul routes and have little chance to recover. Two alarming results have emerged. First, parts of their brains—specifically those related to learning and memory—had physically shrunk, suggesting the destruction of brain cells caused by the biological stress of time-zone travel. Second, their short-term memory was significantly impaired.
Perhaps the most actionable take away I got from studying sleep a bit was on how I consume caffeine. Dr. Walker walks us through how sleep pressure (basically how tired you are) is driven by the buildup in your brain called adenosine. You build adenosine levels throughout the day and as that happens
Caffeine works by successfully battling with adenosine for the privilege of latching on to adenosine welcome sites—or receptors—in the brain. Once caffeine occupies these receptors, however, it does not stimulate them like adenosine, making you sleepy. Rather, caffeine blocks and effectively inactivates the receptors, acting as a masking agent.
Caffeine is a useful tool for sure, but it is important to realize that even though it is blocking the receptors temporarily, it is NOT changing the amount of adenosine being made. So, when the caffeine wears off, it may feel like a ton of bricks hitting.
This makes the timing of caffeine utilization interesting. We drink coffee primarily in the morning when our adenosine is lowest. We might not be getting the most bang for our buck then. For me, I still have a cup in the morning, but thermos the rest with me and start drinking it between 11am-2pm to tamp down that midday lull. I have been pleased with the results.
There was plenty of information on the different stages of sleep, deep (non-REM, NREM) and REM (rapid eye movement). Both are very important.
When it comes to information processing, think of the wake state principally as reception (experiencing and constantly learning the world around you), NREM sleep as reflection (storing and strengthening those raw ingredients of new facts and skills), and REM sleep as integration (interconnecting these raw ingredients with each other, with all past experiences, and, in doing so, building an ever more accurate model of how the world works, including innovative insights and problem-solving abilities).
A few miscellaneous tidbits:
- The changes in deep NREM sleep always precede the cognitive and developmental milestones within the brain by several weeks or months, implying a direction of influence: deep sleep may be a driving force of brain maturation, not the other way around.
- alcohol is one of the most powerful suppressors of REM sleep that we know of.
- Operating on less than five hours of sleep, your risk of a car crash increases threefold. Get behind the wheel of a car when having slept just four hours or less the night before and you are 11.5 times more likely to be involved in a car accident.
- You may find it surprising to learn
that vehicle accidents caused by drowsy driving exceed those caused by alcohol and drugs combined. - With a full night of plentiful sleep, we have a balanced mix between our emotional gas pedal (amygdala) and brake (prefrontal cortex). Without sleep, however, the strong coupling between these two brain regions is lost. We cannot rein in our atavistic impulses—too much emotional gas pedal (amygdala) and not enough regulatory brake (prefrontal cortex).
- Hypersensitivity to pleasurable experiences can lead to sensation-seeking, risk-taking, and addiction. Sleep disturbance is a recognized hallmark associated with addictive substance use.
- sleep quality—especially that of deep NREM sleep—deteriorates as we age. This is linked to a decline in memory.
- Overnight forgetting, rather than remembering, had taken place. The disruption of deep NREM sleep was
therefore a hidden middleman brokering the bad deal between amyloid and memory impairment in Alzheimer’s disease. A missing link. - However, that flu shot is only effective if your body actually reacts to it by generating antibodies. A remarkable discovery in 2002 demonstrated that sleep profoundly impacts your response to a standard flu vaccine.
- The sleep-deprived mice suffered a 200 percent increase in the speed and size of cancer growth, relative to the well-rested group.
I started this with the statement about rhythm being internal. However, we have the ability to choose the path of going along with this pattern or fighting it. We have the ability to match our patterns with that of the
Slowly, the suprachiasmatic nucleus begins to latch on to repeating signals, such as daylight, temperature change, and feedings (so long as those feedings are highly structured), establishing a stronger twenty-four-hour rhythm. By the one-year milestone of development, the suprachiasmatic nucleus clock of an infant has gripped the steering reins of the circadian rhythm.
This short review does not do the content in this book justice. It was a very thorough presentation of much detailed science. Through technology such as the Oura ring, I have been studying how various inputs impact not only sleep duration, but time spent in the different stages. To summarize, I have made significant changes to improve my nightly sleep, and would be happy to help you as well!
This Book Report collection is meant to provide some of the best take-home points from the health and science genre I read. I will continue to go thru my notes of the 160+ and counting (as of January 2019) Kindle books I have on file. To view ALL the notes I saved on this one AND many others without a Book Report post yet, THAT IS ALSO SEARCHABLE, please click here.
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