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  • Writer's pictureAnderson Petergeorge

Why We Sleep: Unlocking the Power of Sleep and Dreams - Dr. Matthew Walker


Overview We sleep for 1/3rd of our lives (almost 30 years!) yet society has deemed "less sleep" as a badge of honour. This book dives into the science around the benefits sleep has but also the life-threatening implications when people sleep less than 8 hours. Lots of well-tested experiments that allow readers even with limited scientific background understand the biology and psychology around sleep.

3 Takeaway Summary

  1. Your mind and body cannot "catch up" on sleep: Sleep doesn't work like a bank ledger book, you cannot sleep 6 hours a day and expect to catch up over the weekend by sleeping 10+. Every night you need the full 7-9 hours for your mind to reset and clear of all the daily toxins for the next day, without that the toxins can permanently stay in the brain. Think of fat that clog arteries that can happen with each additional day of not achieving full sleep.

  2. Alzheimer's has been linked to long-term sleep deprivation: Many people studied including famous politicians such as Margaret Thatcher and Ronald Reagan who publicly would boast about getting 4-5 hours of sleep have suffered severe Alzheimer's. A coincidence? Research proves not.

  3. 10 quick tips to improve your sleep (this is my cheeky way of getting around my 3 takeaway limit per book): i) Stick to a sleep schedule; ii) Don't exercise close to bedtime; iii) Avoid caffeine and nicotine at least 8 hours before bed time; iv) Avoid alcohol before bed; v) Avoid large meals before bed; vi)Avoid naps after 3pm; vii) Reduce room temperature to 65F; viii) Reduce blue light before bed; ix) Increase sun exposure during the day; x) Don't just lie awake in bed


Detailed Notes

  • REM (Rapid eye movement) during then our brain works just as active as if we were asleep. This is when we are dreaming it happens every 90 minutes on average

  • REM is in the second half of your sleep with NREM (Non-rapid eye moment) in the first half. Your brain mainly needs REM to be able to make the connections and to reset. Therefore when you sleep 6 hours as opposed to 8 hours you aren't losing 25% sleep you are losing 60-90% of the sleep you need because the 2 hours you miss is REM sleep

  • NREM Sleep - reflection: storing and strengthening raw ingredients of new facts and skills

  • REM Sleep - 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

  • Routinely sleeping less than six or seven hours a night demolishes your immune system, more than doubling risk of cancer

  • Key lifestyle factor that will determine if you will develop Alzheimer’s disease

  • Countries where sleep at declines most dramatically over the past century are those suffering the greatest increase of physical disease and mental disorders

  • Dreaming provides a unique suite of benefits such as a consoling neurochemical bath that mollifies painful memories and a virtual reality space to meld past and present knowledge, inspiring creativity

  • Your temperature will fluctuate and drop in your body regardless of if you are awake or sleeping based on your natural circadian rhythm

  • However peoples peaks are different in terms of circadian rhythm 40% of ppl are morning types. 30% are evening types and the other 30% lie in between but skew to evening

  • For night owls even though they are awake their pre frontal cortex is asleep which controls high level thought and logical reasoning

  • Night owls and morning larks is not a conscious choice but a genetic fate

  • Melatonin helps corral the brain to get ready to sleep but doesn’t actually help with the sleep itself

  • It takes one day for your body to acclimatize one hour in jet lag. Therefore an 8 hour time difference takes 8 days to acclimatize

  • Melatonin can help with jet lag to use to try and fall asleep

  • Caffeine reduces adenosine which is sleep pressure

  • Caffeine peaks approximately thirty minutes after oral administration. Caffeine has a half life of 5-7 hours

  • Once your liver filters the caffeine expect a large drop in energy levels known as caffeine crash

  • Sleep helps removes the adenosine from your brain and it takes about 8 hours

  • You cannot “sleep back” nights of sleep that you have previously lost is one of the most important take homes of this book

  • Looking at cultures outside of electricity they have a biphasic sleep pattern. They take about 7-8 hours sleep at night followed by 30-60 minutes of sleep in the afternoon

  • In countries where siestas still remain intact, people are more than four times more likely to reach 90 years of age

  • REM sleep provides the coolheaded ability to regulate our emotions each day - a key to what we call emotional IQ depends on getting sufficient REM sleep night after night

  • Research showed students that napped for 90 min before learning were able to retain the information 20% more than those that didn’t

  • Practice plus sleep makes perfect. Sleeping allows your brain to pick up the mistakes you are consciously making and helps fix them

  • More sleep reduces your risk of injury

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

  • Sleeping just 4 hours a day for a week the performance was the same as someone who did back to back all nighters. 400% high chance of micro sleeps while performing

  • Sleeping 4-5 hours a night means you are 11.5x more likely to get in a car accident

  • You cannot catch up on sleep if you’ve missed it in past nights. Your brain doesn’t work like that and this is proven through testing for response even after 3 days after someone’s pulled an all nighter

  • Being drunk and sleep deprived doesn’t just add to how in coordinated someone is but magnifies it’s by more than 30x

  • The recycle rate of a human being is around sixteen hours, after 16 hours the brain slowly starts to fail

  • Just like being drunk the human mind cannot accurately sense how sleep-deprived it is when sleep deprived

  • If you are drowsy while driving please please stop it is as lethal as driving while drunk or even more lethal given you may end of micro sleeping where you body won’t react at all vs when you are drunk you are just slow at reacting so will still have some opportunity to brake a little

  • Power naps can act like caffeine but cannot salvage more complex functions of the brain like learning, memory, emotional stability, decision-making

  • Suicide is the leading reason for death among teens other than car accidents. Therefore having a teen sleep in isn’t necessarily a bad thing as sleep prevents suicidal thoughts

  • Mental disorders create sleep disruption. There is no major psychiatric condition in which sleep is normal

  • If you don’t sleep well the very first night you learn something then you won’t have a good chance of remembering it later - proven through testing two sample groups

  • Insufficient sleep across an individuals life would significantly raise their risk of developing Alzheimer’s disease. It builds amyloid deposits in the frontal region that impacts forgetting rather than remembering. More amyloid deposits the less deep sleep you get which then increases amyloid deposits and the vicious cycle continues

    • Margaret Thatcher and Ronald Reagan who were very vocal of only getting 4-5 hours both went on to develop Alzheimer’s

  • It is proven that heart attacks go up the week after daylights savings time when people especially old people lose an hour of sleep. Heart attacks actually decrease when society gains an hour of sleep in the fall

  • The less you sleep the more likely you are to eat. Less sleep increases levels of circulating endocannabinoids, which is similar to what is produced when you smoke weed aka this is the same as having munchies

  • Those that get 5 hours of sleep are 50% likely to get a cold / virus be those with 7% which were only 18% likely to get the virus

  • REM-sleep dreaming offers a form of overnight therapy. It takes the painful string out of difficult, even traumatic, emotional episodes you have experienced during the day, offering emotional resolution when you awake the next morning.

  • Concentrations of a key stress related chemical called noradrenaline are completely shut off within your brain when you enter a dream like state. That is the only period in the 24 hour clock your brain is devoid of this anxiety triggering molecule.

  • REM sleep performs this elegant trick or divorcing the better emotional rind front he information- rich fruit. We can therefore learn and usefully recall salient life events without being crippled by the emotional baggage that those painful experiences originally carried. Without REM sleep we would be left in a chronic system of anxiety every time we recalled something salient

  • Five key factors have changed how we sleep 1) constant electric light 2) regularized temperature 3) caffeine 4) alcohol

  • Using an iPad 2 hours before bed showed a 23% reduction in melatonin. Also showed a reduction in REM sleep

  • Look into led lights that turn into cooling colours before bed to reduce light received and to increase melatonin

  • The implications of learning can be impacted by alcohol even if we learn things sober. If you learn something and drink alcohol before going to bed you’ll forget 50% of it. This is true even if you drink 3 days after learning something. New memories are not safe typically until 3 days after of proper rem sleep

  • 70-72 degrees is too hot to sleep in. Try and sleep in 65 degrees to help your body cool down it’s core

  • Hot baths helps sleep as it bring blood up to the surface and therefore cooling your core

  • Sleeping pills increase drug tolerance and therefore will create insomnia long term. The sleep you are getting isn’t proper rem sleep as you are using a sedative to knock yourself out not actually getting proper sleep

  • Going to sleep at the same time and waking up at the same time is the most effective way of helping improve your sleep

  • Do not try and workout right before going to bed as it elevates your body temperature for an hour or two after working out which can make it tough for your body to drop your core temperature

  • High sugar diets increase the amount of awareness during the night


12 Tips for Healthy Sleep


  1. Stick to a sleep schedule. Go to bed and wake up at the same time each day. As creatures of habit, people have a hard time adjusting to changes in sleep patterns. Sleeping later on weekends won't fully make up for a lack of sleep during the week and will make it harder to wake up early on Monday morning. Set an alarm for bedtime. Often we set a alarm for when it's time to wake up but fail to do so when it's time to go to sleep. If there is only one piece of advice you remember and take from these twelve tips this should be it.

  2. Exercise is great, but not too late in the day. Try to exercise at least thirty minutes on most days but not later than two to three hours before your bedtime

  3. Avoid caffeine and nicotine. Coffee, colas, certain teas, and chocolate contain the stimulant caffeine, and its effects can take as long as eight hours to wear off fully. Therefore, a cup of coffee in the late afternoon can make it hard for you to fall asleep at night. Nicotine is also a stimulant, often causing smokers to sleep only very lightly. In addition, smokers often wake up to early in the morning because of nicotine withdrawal.

  4. Avoid alcoholic drinks before bed. Having a nightcap or alcoholic beverage before sleep may help you relax, but heavy use robs you of REM sleep, keeping you in the lighter stages of sleep. Heavy alcohol ingestion also may contribute to impairment in breathing at night. You also tend to wake up in the middle of the night when the effects of the alcohol have worn off.

  5. Avoid large meals and beverages late at night. A light snack is okay but a large meal can cause indigestion, which interferes with sleep. Drinking too many fluids at night can cause frequent awakenings to urinate.

  6. If possible, avoid medicines that delay or disrupt your sleep. Some commonly prescribed heart, blood pressure, or asthma medications as well as some over-the-counter and herbal remedies for coughs, colds or allergies, can disrupt sleep patterns. If you have trouble sleeping talk to your healthcare professionals around the drugs you are taking.

  7. Don't take naps after 3pm. Naps can help make up for lost sleep but late afternoon naps can make it harder to fall asleep at night

  8. Relax before bed. Don't overschedule your day so that no time is left for unwinding. A relaxing activity such as reading or listening to music, should be part of your bedtime ritual.

  9. Take a hot bath before bed. The drop in body temperature after getting out of bath may help you feel sleepy, and the bath can help you relax and slow down so you're more ready to sleep.

  10. Dark bedroom, cool bedroom, gadget-free bedroom. Get rid of anything in your bedroom that might distract you from sleep, such as noises, bright lights, an uncomfortable bed, or warm temperatures.

  11. Have the right sunlight exposure. Daylight is key to regulating daily sleep partners. Try to get outside in natural sunlight for at least thirty minutes each day. If possible, wake up with the sun of use very bright lights in the morning.

  12. Don't lie in bed awake. If you find yourself still awake after staying in bed for more than twenty minutes or if you are starting to feel anxious or worried, get up and do some relaxing activity until you feel asleep. The anxiety of not being ablet o sleep can make it harder to sleep



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