Why we sleep
If all animals need to slumber daily in an apparent state of coma, unable to use this time for other tasks, there must be good reasons. As we will see sleep impact many if not all biological processes of the body. This book by Mr Walker is a real eye-opener on what is sleep, what happen when we neglect it and how much better off we are with a good sleep hygiene.
From the evidence presented, I now believe that sleep is at least as important as a good diet and exercise to be healthy and function physically and mentally at one optimum. A must read.
I have amassed more notes than usual so grouping them in four sub-topics, skip to topics of interest.
* What is sleep? * What is the effect of sleep deprivation? * Why is sleep good? How much sleep is needed? * Recent research on REM and dreams?
What is sleep?
- Early riser or late owl is real and genetic, most people are in-between
- Process S - sleep drive, made by adenosine which builds up whilst awake. Caffeine block receptors
- Process C - circadian, a bit more than 24hours long
Melatonin released when sunlight diminishes. Triggers sleep signal but no link with actual sleep process itself
3 types of sleep
- REM - Rapid Eye Movement - most important, see below
- NREM 1,2 - Light sleep - not sure of its role?
- NREM 3,4 - Deep sleep - Consolidate memory, full speed, prune connections
Higher metabolic rate requires greater “cleanup” efforts during sleep
- Key to creativity and ability to control emotions
- Sleep missed cannot be recovered, ever
- Muscle are paralyzed to avoid moving whilst processing memories
- Replay memories about 10 times slower than when awake
- Events connection strengths reinforces
- We make links between distant memories
- REM/NREM ration change
- Circadian circle change
- Early for babies
- Late for teenagers
- Adults in middle
What is the effect of sleep deprivation?
The recycle rate of a human being is around sixteen hours. After sixteen hours of being awake, the brain begins to fail. Humans need more than seven hours of sleep each night to maintain cognitive performance. After ten days of just seven hours of sleep, the brain is as dysfunctional as it would be after going without sleep for twenty-four hours. Three full nights of recovery sleep (i.e., more nights than a weekend) are insufficient to restore performance back to normal levels after a week of short sleeping. Finally, the human mind cannot accurately sense how sleep-deprived it is.
- F. Underwood, Chernobyl, Tankers crashing and many other big names are making big mistakes because of sleep deprivation
- 7h sleep for 10 days gives same impairment than no sleep for 24hours
- 4h sleep for 10 days gives same impairment than no sleep for 48hours
- Skill loss is exponential for 1, 2, 3, nights with no sleep
- Alcohol – Study showed that of something learned on the day, drinking 3 shots in the first evening reduced memory by 50% and more surprisingly drinking 2 nights later instead still reduce memory after a week by 40%!
- More sleep deprivation is very dangerous and it is unethical to experiment on it
Destructive circle as less sleep leads to more amyloid in brain which in turn reduce sleep capabilities - potential mechanism for Alzheimer syndrome.
During sleep, cleaning of brain from toxin occurs
Napping does not remove need for sleep, only alleviate short term adverse effect of lack of sleep
Sleep does not use much less energy that being awake but lack of aggravate craving and reduce satiety leading to extra food intake even if not needed
Immune system works less well with lack of sleep and vaccins generate less response, up to 50% less anti-bodies
Killer cells are less efficient too, making cancer more likely or worse
Sleep even affect telomeres, envelope of DNA, so lack of sleep can be seen as genetic experimentation and make body age faster
Lack of sleep and work
- Tasks take longer, giving less time to sleep
- Creativity lowers
- Ethicality also lowers
Core temperature need to drop before sleep, hot bath or cold room helps
Screen before bed really bad for melatonin release
Sleeping pills are sedative like alcohol and do not trigger sleep but sedated state
Only positive of sleeping pills is subjective sleep quality and time to fall asleep but objective efficiency is not proven and can even create rebounds when stopped.
From “genetics study of genius” found that skill and sleep are strongly correlated
In the USA many school move to very early start with bad consequences for children. Moving start time back from 7.30AM to 8.30AM improved SAT and reduced car accident of 16-18 years old by a whooping 70%
Why do doctors work really long hours in long shift, often being more than 24hours long?
- Started in 1889 by cocaine addict surgeon that started the popular belief that doctor need to see many cases before being able to deal with cases on their own
- 1 in 20 resident will kill a patient due to sleep related mistake
- There is no good reason, except that working more and under high stress is the only way to learn, and this is wrong in many regards
Patients in ICU are in noisy and bright environment, being tested and proded very often, leading to low opportunity for good sleep which is one of the best cure we know of. Same for premature babies.
Suggesting training on sleep in school like for good diet - so far 0% training is the norm
Why is sleep good? How much sleep is needed?
- More important than REM for memory retention
- Memories move from RAM (hippocampus) to storage (cortex)
- Not only we remember better the next day, but even some memories which are lost during a day can re-appear after a night of sleep!
During sleep, spindles from hippocampus communicate with intentionality center in the frontal lobe
For motor skill learning memory goes from hippocampus to unconscious muscle control center
How much sleep is needed?
- Article stating hunter-gatherers only needed 6.75hours but did not consider sleep opportunity i.e. time in bed. Also an adult sleeping only 6.75hours is predicted a life-span of only 60!
- Sleep generally good estimator of life-span, no study showed that sleeping too much as harmful. Ideal seems to be 8h sleep, 16h awake.
12 Advice for daily life
- Habit - fall asleep and wakeup at same time every single day
- No exercise 2-3hours before sleep
- No caffeine 8h before sleep
- No Alcohol in blood by sleep time
- No large meal in the evening
- No sleeping pills
- No nap after 3PM
- Relax without screen 1h before sleep
- Hot bath helps lowering core temperature
- Dark room, cool, gadget free, silence, no clock
- 30-60 bright sunlight early in the day, low light in the evening
- Don’t lie in bed awake more than 20minutes, read is not sleepy
- Tracking devices helpful in the long run
Recent Research on REM and dreams
- MRI invented in early 2000’s
Japanese study match MRI of dream vs. 20 objects and can tell what the dream contains e.g. a car, a man, a house
Dream are not by-product of REM but useful. They nurse emotional and mental health and enable greater creativity.
REM heals emotional wounds and need to match emotion during daytime to sooth them.
REM enables transformation from learning to comprehension.
When awoken in REM, task 90s, people are about 30% better at anagrams i.e. finding relations between elements, but can’t tell where answer comes from.
During REM dreams brain might insert old memories as if asking if this old memory might help with more recent challenges.
Alcohol is one the biggest suppressor of REM sleep
Sommanbulism happens during NREM
1 in 9 suffers from insomnia
REM sleep is what stands between rationality and insanity