Book Summary — Why We Sleep

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1 paragraph summary:

Sleep should be your number one focus ahead of anything else you do. It has an absolutely fundamental role on your health, weight, exercise, recovery, illness, etc — it touches everything you do.

This Thing Called Sleep

Routinely sleeping less than six or seven hours a night demolishes your immune system, more than doubling your risk of cancer. Insufficient sleep is a key lifestyle factor determining whether or not you will develop Alzheimer’s disease. Inadequate sleep — even moderate reductions for just one week — disrupts blood sugar levels so profoundly that you would be classified a pre-diabetic. Short sleeping increases the likelihood of your coronary arteries becoming blocked and brittle, setting you on a path toward cardiovascular disease, stroke, and congestive heart failure.

Sleep disruption further contributes to all major psychiatric conditions, including depression, anxiety and suicidality.

Too little sleep swells concentrations of a hormone that makes you feel hungry while suppressing a companion hormone that otherwise signals food satisfaction.

There are two main factors that determine when you want to sleep:

1. your internal twenty-four-hour clock located deep within your brain
2. chemical substance that builds up in your brain and creates “sleep pressure”

Circadian Rhythm

Every creature on the planet has a sleep/wake cycle.

Your biological circadian rhythm coordinates a drop in core body temperature as you near typical bedtime, reaching its low point, about two hours after sleep onset. However, this temperature rhythm is not dependent upon whether you are actually asleep. If I were to keep you awake all night, your core body temperature would still show the same pattern.

Everyone has their own rhythm.

For some people their peak wakefulness is in the morning — these are “morning types” and make up about 40% of the populace.

Others are “evening types” and account for approx 30% of the population.

It’s a common misconception that being a morning or evening person is a “choice” — but we are bound to these by unavoidable DNA hardwiring.

Melatonin

Melatonin helps regulate the timing of when sleep occurs by systematically signalling darkness. But melatonin has little influence on the generation of sleep itself.

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 governs when the race begins, but does not participate in the race.

Melatonin is not a powerful sleeping aid in and of itself, at least not for healthy, non-jet-lagged individuals. There may be little, if any quality melatonin in a pill. That said, there is a significant sleep placebo effect of melatonin, which should not be underestimated.

For every day you are in a different time zone, your suprachiasmatic nucleus can only readjust by about an hour.

Adenosine

As adenosine builds up in your brain, it creates more sleep pressure. It will increase with every waking minute. You can artificially mute the sleep signal through caffeine.

The levels of circulating caffeine peak approx 30 mins after oral administration. The problematic part is caffeine has an avg half-life (50% is gone) of 5–7 hours.

Note: even decaffeinated stuff has still 15–30% of the caffeine in there.

Once the caffeine is broken down — you get a caffeine crash.

Are you getting enough sleep?

1. when you wake up, could you fall back asleep? then no
2. can you function optimally without caffeine? then yes

If you don’t get enough sleep — your adenosine levels remain high. Like an outstanding debt, the adenosine levels roll over to the next day and the next day etc. which can lead to chronic sleep deprivation.

Sleep

NREM (non-rapid eye movement) and REM (rapid eye movement) recur every 90 mins

Wake state → reception (experiencing and learning)

NREM → reflection (storing and strengthening new facts and skills)

REM → integration (linking, building how the world works, problem-solving)

Genetically we’re designed for biphasic sleep — sleeping twice a day — which prolongs our lives.

Changes of Sleep Across the Life Span

Prior to birth — we spend almost all our time in REM.

Childhood — number of slumber phases is much higher than adults. The daily 24 hour rhythm isn’t developed until age 3–4. NREM proportion increases to 70% and stabilises by late teens to 80%.

Deep sleep is a driving force of brain maturation, not the other way around.

From their late twenties, adults start losing up to 90% of their deep sleep when we’re 70 years old.

We also start losing our sleep efficiency of 90–95% as kids to 70–80% which increases depression and the mortality rate.

Why should you sleep?

Sleeping before learning refreshes our ability to make new memories.

Napping increases learning ability (with stable concentration) and you are better at memorising — both by about 20%.

Sleep post-learning improves retained information by 20–40%. Sleep for learning is an all or nothing thing, not like a bank, if you catch up on sleep a couple of days later, it’s already too late.

In the context of injury, there is no better risk-mitigating insurance policy than sleep.

Post-performance sleep accelerates physical recovery from common inflammation, stimulate muscle repair, and helps restock cellular energy in the form of glucose and glycogen.

Lastly, creativity. Sleep provides a nighttime theatre in which your brain tests out and builds connections between vast stores of information.

Microsleep — sleep deprivation quickly leads to lack of concentration.

Slowness is not the most sensitive signature of sleepiness, entirely missed responses are.

Sleep Deprivation

10 days at 6 hours sleep is all it takes to become as impaired in performance as going without sleep for twenty-four hours straight.

1. subjective sense of how impaired you are is consistently underestimated
2. chronic sleep restriction resets your baseline and will acclimate you to impaired performance, lower alertness and reduced energy levels
3. sleep deprivation amplifies your emotional reactivity by 60% (we swing excessively between positive and negative emotions)
4. reduction of your NREM sleep means your brain can’t clean up toxic debris which is a cause of Alzheimer’s

Heart

One night of just one or two hours less sleep already increases the contracting rate of your heart, increasing systolic blood pressure. It further erodes the fabric of those strained blood vessels, especially the ones in the heart itself.

Eating

The less you sleep, the more you are likely to eat. You become 40% less effective at absorbing sugar → diabetes.

Two hormones are hindered— one which is responsible for making you feel full and the other triggers a hunger sensation.

When you are not getting enough sleep, the body becomes especially stingy about giving up fat. Instead, muscle mass is depleted while fat is retained.

Reproduction

Sleep deprived men have:

• 29% lower sperm count
• sperm itself has more deformities
• smaller testicles
• less testosterone which is responsible for libido and bone density which is required to build muscle

For women:

• 20% drop in follicular releasing hormones which peaks at ovulation and is necessary for conception
• 33% higher rate of abnormal menstrual cycles
• if sleep less than 8 hours when pregnant significantly more likely to have a miscarriage

Cancer

Sleep heals the body against foreign bodies ie diseases including cancer.

Dreaming

Dreaming has two functions (1) nursing our emotional and mental health, (2) problem solving and creativity.

It is not time per se which heals wounds, but instead time spent in dream sleep that provides emotional convalescence.

Generic dreaming does not help in itself, it is dreaming of a specific kind: that which expressly involved dreaming about the emotional themes and sentiments of the walking trauma. It was only that content specific form of dreaming that was able to accomplish clinical remission and offer emotional closure in these patients, allowing them to move forward into a new emotional future, and not be enslaved by a traumatic past.

Deep NREM strengthens individual memories. But it is REM sleep that offers the masterful and complimentary benefit of fusing and blending those elemental ingredients together, in abstract and highly novel ways.

Too much sleep?

Sleep, like food, water and oxygen, may share the relationship of mortality risk when taken to extremes.

Alcohol

• does not help you fall asleep — it is sedation — it’s not the same brainwave state it is more similar to anaesthesia
• it fragments sleep with brief awakenings throughout the night — and is not restorative
• it is one of the most powerful suppressors of REM that we know of

What can you do to get better sleep?

1. reduce caffeine
2. reduce alcohol
3. remove screens from the bedroom
4. lower temperature bedroom
5. regular bed and wake-up time
6. go to bed only when sleepy
7. never lie awake in bed — get up and do stuff
8. avoid daytime napping
9. mentally decelerate before bedtime
10. remove visible clockfaces from your view

The single most effective way of helping improve your sleep is to go to bed and wake up at the same time every day.

Exercise

• don’t exercise just before bed — as body temperature can remain high leading to worse sleep

NASA nap culture

They discovered that naps as short as 26 minutes in length still offered a 34% improvement in task performance and more than 50% increase in overall alertness. These results hatched the so-called NASA nap culture.

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