These are the key points I found in the book "Why We Sleep" by Dr. Matthew Walker.
PART 1: WHAT IS SLEEP
7-9 hours of sleep per day
sleep vs. evolution (unintuitive)
circadian rhythm (>24 hours), biological clock, suprachiasmatic nucleus, melatonin
adenosine (sleep drug)
jet lag: eastward (harder) vs. westward travel (easier); falling asleep ahead of usual time is harder
caffeine, vs. adenosine, processed by liver, half life of 7-8 hours
morning larks vs. night owls
How to identify sleep? (1) lack of external awareness; (2) easy to reverse (vs. anaesthesia, coma, hibernation, death); (3) posture; (4) time; (5) relaxed muscles; and () time distortion.
Sleep stages:
- 90 minutes cycles
- REM (dream sleep, paradoxical sleep) and NREM stages
- AM (low frequency, coordinated pulses, deep sleep, during NREM) vs. FM (high frequency, REM)
- REM atonia: muscle paralysis during REM sleep; to avoid acting out the dreams
- wakefulness (reception), NREM sleep (reflection), REM sleep (integration)
Differences in sleep across species: (1) duration (4--22 hours); (2) pattern (monophasic, biphasic); (3) composition of NREM/REM stages); and (4) extreme situation (e.g. migratory birds undergo sleep fast, one half or both halves of the brain inactive).
Sleep rebound (catchup lost sleep)
Human sleep: (1) includes higher proportion of REM stages; (2) exclusive terrestrial sleepers.
PART 2: WHY SHOULD YOU SLEEP
Memory (NREM stage): (1) free-up temporary storage (hippocampus); (2) consolidate memory to permanent storage (cortex); and (3) muscle memory, motor skills.
Creativity (REM stage): dream sleep
power nap: not a substitute for full-night sleep
microsleep - e.g falling asleep at the wheel
sleep inertia
sleepless elite
Consequences of sleep deprivation: (1) lack of concentration; (2) emotional irrationality; (3) psychiatric, mental illnesses (e.g. schizophrenia, depression, bipolar disorder); (4) higher risk of heart attack, diabetes, weight gain
PART 3: DREAM
- psychotic: hallucination, delusional, disoriented , labile (mood swing), amnesia
- not a replay of daytime events
- strong activation in visual, motor, emotional and memory (hippocampus) regions of the brain, yet a relative deactivation of rational thought (prefrontal cortex)
- repair emotional wounds, social skills, PTSD
- creativity, problem-solving skills (e.g. Mendeleev), "sleep on it"
PART 4: FROM SLEEPING PILLS TO SOCIETY TRANSFORMED
Sleep disorders (Chapter 12): (1) somnambulism (sleep walking; trouble with REM sleep); (2) insomnia (inability to sleep; emotional distress); (3) narcolepsy (excessive sleeping; trouble with release of orexin); (4) fatal familial insomnia (hereditary); and (5) sleep apnoea.
Sleep indicators (for the brain): (1) reduction of heart rate; (2) reduction of blood pressure; (3) reduction of metabolism (no late night dinner); and (4)
lowering of core body temperature.
sleep opportunity
beauty sleep
short sleep
sleep deprivation = food deprivation
Improve sleep quality (Chapter 13):
- melatonin release increases with sunset (drop in sunlight, temperature)
- humans are predominantly visual creatures
- lighting (yellow incandescent vs. blue LED; lowered, dim light in the evening)
temperature (wash face, feet and hands with cold water; hot bath;)
- 18.3 degree Celsius is the optimum temperature for sleep.
- alcohol (sedation and not sleep)
- avoid alarm clock, avoid snooze button
"Modern society has taken nature's perfect solution (sleep) and divided it into two problems: (1) lack of sleep at night, (2) inability to remain fully awake during the day."
Sleeping pills (Chapter 14): (1) do not induce natural sleep; (2) not the perfect cure for insomnia; (3) belong to the class of drugs called sedatives; (4) rebound insomnia; and (5) withdrawal symptoms.
CBT-I (cognitive behavioural therapy for insomnia)
Health Trinity: balanced diet, proper exercise, sound sleep
do not go to bed too hungry or too full
avoid excess carbs, sugar
get workout a few hours before bedtime
Sleep and Society (Chapter 15): (1) sleep loss declared as global health epidemic (WHO); (2) sleep deprivation vs. ADHD; (3) relaxed approach to work schedules; (4) sleep deprivation among employees, students, doctors; and (5) 22 hours without sleep = legally drunk.
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