I just finished reading Why We Sleep. This book is a (can’t avoid the dad pun) wake up call about how essential sleep is. Between my constant anxiety and a lot of the self-improvement literature I have read, I sometimes regarded my fondness for sleep as a sort of weakness. No more. This book is essential knowledge.

My only concern with it is that it feels at times almost too preachy, and it’s hard not to feel you’re already on your way to an early death because of the relatively mild sleep deprivation you’ve already gone through by this point of your life (especially if you are a parent of a young kid). But the book is priceless and I shall endeavor to heed it, by sleeping as much and as well as I can.

Here are my notes:

• 2/3 of adults throughout developed nations don’t get the recommended eight hours of nightly sleep.
• “Routinely sleeping less than six or seven hours a night demolishes your immune system, more than doubling your risk of cancer.”
• Note: interesting to see cancer prevention as the role of the immune system!
• Lack of sleep increases Alzheimer risks, disrupts sugar levels and lzzAincreases the chances of cardivascular disease. Also, lack of sleep “contributes to all major psychiatric conditions”.
• “Too little sleep swells concentrations of a hormone that makes you feel hungry while supressing a companion hormone that otherwise signals food satisfaction.”
• Lack of sleep also makes weight loss be more muscle loss than fat loss.
• “The elastic band of sleep deprivation can stretch only so far before it snaps.”
• The WHO has declared a sleep loss epidemic throughout industrialized nations.
• Lack of sleep can physically and directly kill you.
• “Society’s apathy toward sleep has, in pasrt, been caused by the historical failure of science to explain why we need it.”
• Sleep was a scientific mystery, compared to the three main other drives (eat, drink, reproduce).
• “When you are asleep, you cannot gather food. You cannot socialize. You cannot find a mate and reproduce. You cannot nurture or protect your offspring. Worse still, sleep leaves you vulnerable to predation.”
• “If sleep does not serve an absolutely vital function, then it is the biggest mistake the evolutionary process has ever made.”
• Every species studied to date sleeps.
• “We sleep for a rich litany of unctions, plural”
• If we derive multiple benefits from being awake and achieve many things during that period, the same goes for sleep.
• Sleep is fundamental for both brain and body.
• In the “health trinity” of diet, exercise and sleep, sleep is “the preeminent force”. “It is difficult to imagine any other state – natural or manipulated – that affords a more powerful redressing of physical and mental health at every level of analysis.”
• So far, every aspect of an organism has been shown to be benefitted by sleep.
• “sleep is the single most effective thing we can do to reset our brain and body health each day – Mother Nature’s best effort yet at contra-death.”
• “Ultimately, medicine wasn’t for me, as it seemed more concerned with answers, whereas I was always more enthralled by questions.”
• “A scarcely believable truth began to emerge – nobody actually knew the clear reason why we needed sleep, and what it does. (…) I decided I would try to crack the code of sleep.”
• “With genuine naivete, not hubris, I believed I would find the answer within two years. That was twenty years ago. Hard problems care little about what motivates their interrogators; they meter out their lessons of difficulty all the same.”
• “Now (…) we have many of the answers.”
• “These sleep revelations (…) will offer all the proof you need about the vital importance of sleep.”
• Part 1: what/how/why of sleep. Part 2: sleep deprivation. Part 3: dreams. Part 4: sleeping disorders.
• “I lay out a road map of ideas that can reconnect humanity with the sleep it remains so bereft of- a new vision for sleep in the twenty-first century.”
• “feel free to ebb and flow into and out of consciousness during this entire book.”
• Two main factors determine wakefulness and sleep: one is a signal from our internal clock; the other is a substance that builds up and creates “sleep presssure” the longer you have been awake.
• “It is the balance between these two factors that dictates how alert and attentive you are during the day”
• Circadian (means: around a day) rhythm “Every living creature on the planet with a life span of more than several days generates this natural cycle.” Circadian rhythm influences many other things, not just sleep.
• De Mairan discovered the internal clock of living beings by placing a Mimosa pudica plant in the dark and noticing that it continued to do the same patterns of movement in total darkness.
• “Somewhere within the plant was a twenty-four hour rhythm generator that could track time without any cues from the outside world, such as daylight.”
• Kleitman and Richardson: discovery of the human circadian rhythm, in a dark cave for 32 days. Prolonged wakefulness (15h) followed by sleep (9h). Richardson, in his 20s, had a cycle of 26-28h. Kleitman, in his 40s, was closer to 24h but stil longer.
• Average human clock: 24:15h. “The light of the sun methodically resets our inaccurate internal timepiece each and every day”.
• “the reason most living species likely adopted a circadian rhythm is to synchronize themselves and their activities (…) with the daily orbital mechanics of planet Earth spinning on its axis”
• Other cues can also be used by the brain to set the internal rhythm: zeitgebers (time givers). Food, exercise, temperature fluctuations, regularly timed social interactions.
• Biological clock: suprachiasmatic nucleus. Located on top of the crossing point in the middle of the brain between the two nerves that come from each eyeball.
• 20k neurons on the clock, vs 100b on the entire brain. “This tiny clock is the central conductor of life’s biological rhythmic symphony – yours and every other living species.”
• Body temperature rises from a minimum at 3-4am to a plateau at 14, then rises again until peaking at 18-19.
• Morning types (larks, 40% of the pop) vs evening types (owls, 30%). Remaining 30% are in the middle, “with a slight leaning towards eveningness”. These are chronotypes.
• “When a night owl is forced to wake up too early, their prefrontal cortex remains in a disabled, “offline” state.”
• Chronotype strongly determined by genetics.
• Owls suffer because 1) they are considered lazy; 2) standard work schedules don’t work for them.
• “Greater ill health caused by a lack of sleep therefore befalls owls”
• Having different chronotypes allows a tribe to have someone awake for half the night, so there’s only 4 hours of vulnerability when everyone’s asleep (about 1am to 5am) rather than eight if everyone sleeps at the same time.
• Melatonin released after dusk. “Melatonin acts like a powerful bullhorn, shouting out a clear message to the brain and body: “It’s dark, it’s dark!””. Sleep onset.
• “But melatonin has little influence on the generation of sleep itself.” “For these reasons, melatonin is not a powerful sleeping aid in and of itself, at least not for healthy, non-jet-lagged individuals”
• “the placebo effect is, after all, the omst reliable effect in all of pharmacology.”
• With dawn, “a brake pedal is applied to the pineal gland, thereby shutting off the release of melatonin.”
• Jet lag: biological time lag. We feel sleep when we shouldn’t and alert when we shouldn’t, because our body didn’t adapt to the new timezone.
• “This is jet lag: you feel tired and sleepy during the day in the new time zone because your body clock and associated biology still “think” it is nighttime. At night, you are frequently unable to sleep solidly because your biological rhythm still believes it to be daytime.”
• Adaptation rate: one hour per day.
• Harder when travelling eastward than westward. It is easier to stay up later than to go to bed earlier; and our internal clock has days longer than 24h, which makes a difference.
• Constant travel across timezones might destruct brain cells related to learning and memory; and it also affects short-term memory.
• Melatonin is useful in the context of jet lag, to trigger the advent of night time for the biological clock.
• Adenosine is the hormone that determines sleep pressure (desire to sleep). “Think of adenosine as a chemical barometer that continously registers the amounts of elapsed time since you woke up this morning.”
• Caffeine mutes the effect of adenosine. “caffeine is t he most widely used (and abused) psychoactive stimulant in the world. It is the second most traded commodity on the planet, after oil. The consumption of caffeine represents one of the longest and largest unsupervised drug studies ever conducted on the human race, perhaps rivaled only by alcohol, and it continues to this day.”
• Caffeine binds to the adenosine receptors in the brain, blocking them.
• Caffeine peaks approximately 30 minutes after intake. It’s half life is 5-7 hours.
• Caffeine “is one of the most common culprits that keep people from falling asleep easily and sleeping soundly thereafter, typically masquerading as insomnia”
• Decaf contains 15-30% of the dose of a regular cup of coffee.
• Some people have a faster acting enzyme to degrade caffeine faster. The older we are, the longer it takes to clear out caffeine and the more sensitive we are to it when we want to fall asleep.
• While caffeine blocks the receptors, adenosine still builds up, so it will hit you harder when the caffeine goes away.
• Spiders making webs under the influence of different drugs: caffeine impaired them the most, more than LSD, marijuana and speed.
• “Caffeine is also the only addictive substance that we readily give to our children and teens”
• “If you feel as though you could fall asleep easily midmorning, you are very likely not getting enough sleep, or the quality of your sleep is insufficient.”
• The circadian rhythm and the adenosine concentration are coupled, but don’t interact directly with each other.
• “During sleep, a mass evacuation gets under way as the brain has the chance to degrade and remove the day’s adenosine.” After eight hours, thi s is usually accomplished.
• “Following that full night of sleep, you are now ready to face another sixteen hours of wakefulness with physical vigor and sharp bain function.”
• During all nighter, the second wind comes when your circadian rhythm starts to perk up, despite your adenosine being very high. The worst moment, about 6am, is when your circadian rhythm is at its lowest and adenosine is very high already.
• “how do you know whether you’re routinely getting enough sleep? (…) Firsst, after waking up in the morning, could you fall back asleep at 10 or eleven a.m.? If the answer is yes”, you are likely not getting sufficient sleep quantity and/or quality. Second, can you function optimally without caffeine before noon? If the answer is “no”, then you are most likely self-medicating your state of chronic sleep deprivation.”
• Adenosine debt, carried from one day to another. “This outstanding sleep obligation results in a feeling of chronic fatigue, manifesting in many forms of mental and physical ailments that are now rife throughout industrialized nations.”
• If you need an alarm clock to wake up, that’s also an indicator of sleep debt.
• Most common sleeping disorders: insomnia, followed by sleep apnea (including heavy snoring). Seek a referral to a sleep specialist. Don’t use sleeping pills as your first option.
• Sleep is denoted by: specific position, lowered muscle tone, no communiction or responsivity, easily reversible, follows a timed pattern.
• From an internal perspective: loss of external awareness (the senses keep on sending info to the brain but most of the signals are blocked in the thalamus); and time distortion (loss of time track at a conscious level).
• Dreams are perceived as longer that they really are judging by clock time: “at just half or quarter the speed”. This may be the reason for the perceived lengthiness of dreams.
• To scientifically measure sleep, electrodes are attached to measure 1) brain activity; 2) eye movement; 3) muscle activity.
• Aserinsky & Kleitman discovered the two stages of sleep: REM (rapid eye movement sleep) and NREM (non REM). Four levels of NREM depth, the greater the number, the harder to wake up.
• Cycle/battle between two types of sleep happens every 90 minutes, starting with NREM and followed by REM. NREM starts with the upper hand but then the balance shifts to REM as the night goes by.
• “It sounds like an exhausting amount of evolutionary hard work to have designed such a convoluted system, and put it into biological action.”
• Same pattern of sleep in mammals and birds.
• NREM clears out unnecessary neural connections, REM builds or strengthens new connections.
• If you wake up too early, you miss out on REM. If you go to bed too late, you miss on NREM.
• During wakefulness and REM, all of the brain is firing quickly without discernible pattern. But during NREM, the waves of activity slow down and synchronize. When that wave goes down, there are “sleep spindles”, a trilling of activity “at the tail end of each individual slow wave.”
• The NREM waves originate from the middle of the frontal lobes, from the front to the back of the brain. These waves show a brain working in complete synchrony. “It is an active, deliberaate, but highly synchronous state of brain activity. It is a near state of nocturnal cerebral meditation, though I should note that it is very different from the brainwave activity of waking meditative states.”
• The slow waves “open up communication possibilities between distant regions of the brain, allowing them to collabiratively send and receive their different repositories of stored experience.” This includes the creation of long term memories.
• Waking state: reception of the outside world. NREM: reflection.
• What happens during REM? “REM sleep brain activity is an almost perfect replica of that seen during attentive, alert wakefulness”. Some parts of the brain are up to 30% more active during REM than when awake.
• During REM, the brain processes information coming from “signals of emotions, motivations and memories (past and present) are all played out on the big screens of our visual, auditory and kinesthetic sensory cortices in the brain.” REM sleep is integration.
• The telltale of REM is complete muscle relaxation: you’re in effect completely paralyzed, except for involuntary muscles. During NREM, there’s still some muscular tension. “You have, in effect, become an embodied prisoner, incarcerated by REM sleep.” The purpose of atonia (lack of muscle tone) is to prevent you “from acting out your dream experience. (…) You can well imagine the calamitous upshot of falsely enating a dream fight, or a frantic sprint from an approaching dream foe, while your eyes are closed and you have no comprehension of the world around you.”
• In some people the paralysis mechanism can fail. This is how we know that the impulses are sent to the muscles, but blocked.
• The eye movements are not matched to the visual experience of dreams, but “intimately linked with the physiological creation of REM sleep” (details about this in chapter 9)
• Dobzhansky: “Nothing in biology makes sense except in light of evolution.”
• Every animal species sleep. “Sleep is universal.” Sleep predates all vertebrate life. Bacteria that live more than a day have active/passive phases matching “the light-dark cycle of our planet.”
• Author’s hypothesis: “sleep was the first state of life on this planet, and it was from sleep that wakefulness emerged.”
• Four differences in sleep among species: total amount of time (elephants: 4, humans ~8, tigers/lions ~15, brown bat ~19). No clear cut single variable that explains this. Even close species can have very different needs of sleep time. And near identical sleep times across very different species. brain complexity relative to body size is correlated with more sleep.
• Species that sleep more don’t have a lower quality sleep. If anything, they have higher quality sleep.
• “anomalous species may hold some of the keys to unlocking the puzzle of sleep need.”
• Second difference: composition of sleep. Only birds and mammals have full-blown REM. “REM sleep seems to have emerged to support functions that NREM sleep alone coul d not accomplish, or that REM sleep was more efficient at accomplishing.”
• Aquatic mammals don’t have REM sleep. This makes sense, because REM paralyzes the body and that would stop swimming.
• Pinnipeds (such as fur seals) have REM in land, but barely any in the ocean.
• “REM sleep does not appear to be feasible or needed by aquatic mammals when in the ocean.”
• Ancient mammals (egg-laying/monotremes) have a basic version of REM sleep that happens at the base of the brain. The author suspects there’s REM sleep in aquatic mammals, but as of yet undetected.
• REM sleep in mammals and birds might have developed independently.
• “When a theme repeats in evolution, and independently across unrelated lineages, it often signals a fundamental need.”
• Proto REM detected in a lizard. If the finding is replicated, it could mean that the seed for REM was present in a common ancestor of mammals and birds.
• NREM came first, evolutionarily. Both REM and NREM are important. When sleep deprived, two things happen: we sleep more the next night (10-12h for humans, compared to a normal 8) and, second, “NREM sleep rebounds harder”. But on subsequent nights, REM becomes more prevalent than NREM. “We try to recover one (NREM) a little sooner than the other (REM), but make no mistake, the brain will attempt to recoup both” s
• Sleep lost is never regained. “That humans (and all other species) can never “sleep back” that which we have previously lost is one of the most important take-homes of this book”
• Third difference: way of sleep. Cetaceans sleep with half their hemisphere at a time. “Even with half of the brain asleep, dolphins can achieve an impressive level of movement and even some vocalized communication.”
• Cetaceans show sleep is non-negotiable. Birds also sleep with half a hemisphere, to keep an eye on things. When flocks group, birds inside the flock will sleep with both hemispheres, while those on the sides sleep with one half (they then switch spots to switch which side of the brain and eye gets rest).
• Humans have a mild unihemispheric sleep when sleeping in unfamiliar surroundings: one hemisphere sleep slighter than the other.
• REM cannot be split across sides of the brain, not even in birds. Unihemispheric sleep is only for NREM.
• The fourth difference in sleep is the reduction of sleep patterns “under rare and very special circumstances (…) The inrequent situation happens only in response to extreme environmental pressures or challenges.”
• Examples: starvation and migration. “In-flight, migrating birds will grab remarkably brief periods of sleep lasting only seconds in duration. (…) If you’re wondering, humans have no such similar ability.”
• “Humans are not sleeping the way nature intended. The number of sleep bouts, the duration of sleep, and when sleep occurs have all been comprehensively distorted by modernity.”
• In developed countries, monophasic sleep pattern at night (on average less than 7 hours).
• Hunter gatherers have a biphasic pattern: long sleep at night (7-8 hours, with 7 net hours of sleep), and a 30-60 minute nap in the afternoon. In some places, naps happen only during the summer season.
• Hunter gatherers fall asleep 3 hours after sundown, around 9pm, and wake up at about dawn.
• In industralized countries, we go to sleep just after midnight but still wake up in the morning. And few can take afternoon naps, “further contributing to our state of sleep bankruptcy.”
• Biphasic sleep is “deeply biological”, at around mid-afternoon.
• In the late 17th and late 18th centuries, “Wetern EUropeans would take two long bouts o sleep at night, separated by several hours of wakefulness.” It seems to have been a cultural phenomenon.
• A study of the health consequences of abandoning siesta in Greece showed a sharp increase of heart disease and mortality. “when we are cleaved from the innate practice of biphasic sleep, our lives are shortened.”
• Human sleep is special: compared to other primates, we sleep less (8h vs 10-15h in other species) and we have a much higher rate of REM sleep (20-25%, compared to 9%). Humans sleep on the ground, but other primates sleep in treetop sleep nests. “This body balancing act was the challenge and danger of tree sleeping for our primate forebears, and it markedly constrained their sleep.”
• Homo erectus was probably the first ground sleeper. This was probably enabled by fire, which kept away predators and vermin.
• There are species that have more REM than humans, but none do it in a brain that has the complexity of the human brain.
• REM sleep enhances emotional circuits (enabling higher sociocultural complexity) and cognitive intelligence. The author posits that sleep was a great forcing in the rise of humans.
• Coolheadedness and emotional control requires REM sleep.
• “I will go a step further and suggest that this is the most influential function of REM sleep in mammals, perhaps the most influential function of all types of sleep in *all mammals, and even the most eminent advantage ever gited by sleep in the annals of all planetary life. The adaptive benefits conferred by complex emotional processing are truly monumental, and so often overlooked.” This benefit compounds exponentially for the collective of the species.
• REM also contributes creativity. “We can awake the next morning with new solutions to previosly intractable probelms or even be infused with radically new and original ideas.”
• Chimpanzees have been around for 5mya longer than humans, but despite “aeons of opportunity time”, they haven’t developed as we did. In terms of evolutionary advantage, the superior emotional handling seems to be more powerful than creativity, because “unless creative, ingenious solutions can be shared (…) then creativity is far more likely to remain fixed within an individual, rather than spread to the masses.”
• Positive feedback loop: more REM, more creativity/emotional intelligence, better survival strategies, more capacity for REM sleep. Ever growing social groups.
• Humans in the womb sleep almost all the time, even when kicking – these kicks mostly happen because the paralyzing mechanism that is triggered during REM is still not fully developed. In utero, there’s 6 hours of NREM, 6 of REM and 12 of “an intermediary sleep state that (…) certainly is not full wakefulness.”. In the third trimester there might be 2-3 hours of wakefulness per day.
• In the last two weeks of pregnancy, the fetus will consume up to 12 hours of REM a day (a high never reached again in its lifetime). “This phase of development, which infuses the brain with masses of neural connections, is called synaptogenesis, as it involves the creation of millions of wiring links, or synapses, between neurons. By deliberate design, it is an overenthusiastic first pass at setting up the mainframe of a brain.” This also happens in all other mammals.
• “Biologically, it is as if the day and night are far less light adn dark, respectively, for autistic individuals.” Autistic children often sleep less, and particularly, less REM sleep (3-50% deficit).
• Alcohol, when consumed by a pregnant woman, reduces REM sleep in unborn babies. The same happens with nursing babies.
• “Infants and young kids display polyphasic sleep”
• “the older a child gets, the fewer, longer, and more stable their sleep bouts become.” The reason for this is that the circadian rhythm takes more time to develop. By 3-4 months, it is in place to a certain extent. By one year of age, the rhythm is firmly in place. By age four, the circadian rhythm is dominant.
• REM sleep is 50% in six month olds, but decreases to 30% in five year olds. It will continue until stabilizing in adulthood to 20%. After the “overzealous” REM wiring, a lot of wiring is pruned by NREM, using experience as a guide. “It is not a complete redo of the network, and much of the original structure will remain in place.”
• Fein berg longitudinal study of kids & teenagers over time. Deep sleep intensity increases in adolescence, then drops again. “deep sleep may be a driving force of brain maturation, not the other way around.”
• Deep sleep became more intensive at the back of the brain (visual/spatial perception) and then moved forward as adolescence progressed. So the last part of the brain to pass into adulthood was the frontal cortex. “His findings helped explain why rationality is one of the last things to flourish in teenagers”
• Deep sleep is causal, not correlated, with brain development in adolescence. Caffeine retards and disrupts this process.
• Teeneagers that later developed schizophrenia showed greatly impaired NREM sleep.
• Younger children are larks, but adolescents tend to owlishness, even more than adults. A 9 year old would be asleep by 9pm, but a 16 year old might feel sleep towards midnight. Early schooltimes are damaging to adolescents and should be prevented.
• “No child needs caffeine.”
• “That older adults simply need less sleep is a myth. Older adults appear to need just as much sleep as they do in midlife, but are simply less able to generate that (still necessary) sleep.”
• Core problems with sleep in adults: reduced quantity/quality; 2) reduced sleep efficiency; 3) disrupted timing of sleep.
• In thirties and forties, there’s a reduction of depth and amount of NREM sleep. By the late forties, you hve only 30% of the deep sleep you had as a teenager. By age 70, you’ll lose 80-90% of it.
• “not all medical problems of aging are attributable to poor sleep. But far more of our age-related physical and mental health ailments are related to sleep impairment than either we, or many doctors, truly realize or treat seriously.”
• Sleep fragmentation is usually due to weakened bladders. Reduced liquid intake at night is helpful in that regard. Sleep efficiency: % of time you are asleep when in bed. Teenagers have an efficiency of about 95%. Good efficiency for adults is 90%. It can drop to as much as 70% for older adults.
• Seniors drift toward larkiness. If they nap in the early evening, they then lose sleep pressure for having a solid night sleep. There are methods to shift the circadian rhythm later in seniors, using blue light in the late afternoon hours. Melatonin is also useful for seniors.
• The loss of deep sleep with age has a (yet) elusive cause.
• The brain doesn’t deteriorate uniformly with ageing (atrophy). The areas generating deep sleep are those that deteriorate first (middle-frontal regions just above the nose).
• “It was a saddening conirmation of my theory: the parts of our brain that ignite healthy deep sleep at night are the very same areas that degenerate, or atrophy, earliest and most severely as we age.”
• “Poor memory and poor sleep in old age are (…) significinatly interrelated.”
• The brain atrophy accounts for 60% of sleep loss, but the other 40% is still being researched.
• “Said unkindly, older adults don’t have much further to fall in terms of getting worse (…) making it difficult to estimate the real performanc eimpact of sleep deprivation.”
• “We do not assume that older individuals need weaker bones just because they have reduced bone density.”
• “Failed by the lack o public education, most of us do not realize how remarkable a panacea sleep truly is.”
• Macbeth: “[sleep is] the chief nourisher in life’s fesat.”
• Sleeping creates long term memories, hence enabling learning ability.
• After sleeping, the hippocampus (short term memory) is cleared and its contents transferred to the cortex (long term storage), so you are ready to learn again. The sleep “spindles” show the transfer of information.
• For fact based memory, deep NREM (early night sleep) wins out against REM.
• Even facts seemingly lost just after learning can be recalled and restored by sleep.
• Therapies to improve memory benefits of sleep: sleep stimulation & targeted memory reactivation.
• “By boosting the electrical quality of deel-sleep brainwave activity, the researchers almost doubled the number of facts that individuals were able to recall the following day, relative to those participants who received no stimulation. Applying stimulation during REM sleep (…) did not offer similar memory advantages.”
• The same can be done with auditory clicks that match the brainwaves. It can also be done by a slowly rocking bed.
• Targeted memory reactivation, for specific memories.
• Each learning piece is paired with a sound. When asleep at NREM, the sounds are replayed at low volume. This enhances the retrieval of the associated memories the next day. This doesn’t work during REM.
• Sleep also helps forget certain things (including traumatic experiences).
• “sleep was far more intelligent thatn we had once imagined. (…) sleep is able to offer a far more discerning hand in memory improvement: one that preferentially picks and chooses what information is, and is not, ultimately strengthened.” This is done by tags associated to memories during learning (or identified during sleep).
• NREM is responsible for retaining more or forgetting more certain facts. “Exactly how sleep spindles accomplish this clever memory trick remains unclear.”
• Interchange between hippocampus (memory storage) and frontal lobe (intentionality of memorization) happen 10-15 times per second during NREM sleep.
• Selective weakening of memories could be useful for treating trauma and substance abuse.
• Motor skills: “Muscle memory is, in fact, brain memory. Training and strengthening muscles can help you better execute a skilled memory routine. But the routine itself – the memory program – resides firmly and exclusively within the brain.”
• “I will be practicing a particular piece (…) and I cannot seem to mster it. (…) when I wake up the next morning and sit back down at the piano, I can just play, perfectly.”
• Sleep improves motor skill performance after practice. “your brain will continue to improve skill memories in the absence of any further practice. (…) yet, that delayed, “offline” learning occurs exclusively across a period of sleep”. Practice + sleep makes perfect.
• “Sleep had systematically identified where the difficult transitions were in the motor memory and smoothed them out.”
• Learning of skill transfers knowledge to “brain circuits that operate below the level of consicousness.”
• Overnight motor-skill enhancement comes from stage 2 NREM, especially the one in the last two hours of 8 hours of sleep (5-7am if you sleep at 11pm).
• “Those last two hours of sleep are precisely the window that many of us feel it is okay to cut short to get a jump start on the day. As a result, we miss out on this feast of late-morning sleep spindles.”
• “if you don’t snooze, you lose.”
• Sleep is strongly and inversely correlated with probability of injuries in athletes.
• Recovery of mobility after a stroke heavily depends on stage 2 NREM sleep. “Ongoing sleep quality predicts the gradual return of motor function, and further determines the relearning of numerous movement skills.”
• “There is much that sleep can do that we in medicine currently cannot.”
• “Sleep provides a nighttime theater in which your brain tests out and builds connections between vast stores of information. This task is accomlished using a bizarre algorithm that is biased toward seeking out the most distant, nonobvious associations, rather like a backward Google search.”
• Guinness stopped recognizing the sleep deprivation world record.
• “No facet of the human body is spared the crippling, noxious harm of sleep loss.”
• Chronically sleep restricted individuals: less than seven hours of sleep a night on a routine basis.
• “During a microsleep, your brain becomes blind to the outside world for a brief moment”
• Lack of sleep’s most telling effect on cocentration is n ot slowness, but moments where concentration is entirely missing.
• By day 11, those who slept 4 hours a night had the performance of someone going without sleep for 48 hours.
• Ten days of 6 hours of sleep a night shows a drop in concentration to not sleeping for 24 hours.
• Sleep deprived people tend to underestimate their tiredness and performance disability.
• “With chronic sleep restriction over months or years, an individual will actually acclimate to their impaired performance, lower alertness, and reduced energy levels.”
• “Sixty years of scientific research prevent me from accepting anyone who tells me that he or she can “get by on just four or five hours of sleep a night just fine.””
• .08 percent blood alcohol has a similar effect on concentration than being awake for an entire night.
• “Each hour of sleep lost vastly amplifies that crash likelihood, rather than incrementally nudging it up.”
• Mixing tiredness and alcohol consumption multiplies concentration loss.
• “The recycle rate of a human being is around sixteen hours. After sixteen hours of being awake, the brain begins to fails. (…) 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.”
• Drowsy driving generates more accidents than alcohol and drugs combined.
• Microsleep makes you stop reacting altogether, instead of having a slower reaction time as with drugs/alcohol.
• Accident is “unexpected event that happen by chance or without apparent cause.”
• Drowsy driving deaths are “predictable and the direct result of not obtaining sufficient sleep.”
• “Some people only get one chance to fall asleep at the wheel before losing their life.”
• “The most dangerous time of flight is landing” (68% of all catastrophic crashes).
• Power naps work better at the beginning of a bout of sleep deprivation than at the middle or towards the end: prevention vs cure. From the studies done on naps on pilots, the term “power naps” emerged.
• “Brief power naps have become synonymous wilth the inaccurate assumption that they allow an individual to forgo sufficient sleep (…) especially when combined with the liberal use of caffeine.” There’s no scientific evidence for this. “neither naps nor caffeine can salvage more complex functions of the brain, including learning, memory, emotional stability, complex reasoning, or decision-making.”
• A fraction of 1% of the population have a genetic mutation that allows them to naturally survive on six hours of sleep (sub-variant of gene BHLHE41).
• Emotional reactivity can be over 60% larger on sleep deprived individuals. “it was as though, without sleep, our brain reverts to a primitive pattern of uncontrolled reactivity.”
• The cause for this is that the coupling between the prefrontal cortex (rational thought) and the amygdala (emotional center) is enhanced and maintained through sleep. “Without sleep, however, the cstrong coupling between these two brain regions is lost.”
• This happens both with a sleepless night and with chronic, low-grade sleep deprivation.
• Hedonic areas of the brain also become hyperactive in sleep-deprived individuals. This can also lead to extreme positive feelings and risky behavior, including addictions.
• Suicide is second leading cause of death in young adults in developed nations, after car accidents.
• “insufficient sleep during childhood significantly predicts early onset of drug and alcohol use in that same child during their later adolescent years”
• “sleep loss and mental illness is best described as a two-way street of interaction, with the flow of traffic being stronger in one direction or the other, depending on the disorder.” Sleep remains neglected as a factor in treating psychiatic illness.
• Lack of sleep can trigger a manic or depressive episode in a bipolar person.
• “By regularizing and enhancing sleep, Harvey has stepped this patients back from the edge of crippling mental illness.”
• Anhedonia: “inability to gain pleasure from normally pleasurable experiences, such as food, socializing, or sex.”
• “The best bridge between despair and hope is a good night’s sleep.” — Joseph Cossman
• Sleep deprivation attacks the hippocampus (the memory “inbox”) and blocks its capacity for absorbing new information.
• “if you don’t sleep the very first night after learning, you lose the chance to consolidate those memories”
• Two most feared diseases in devloped nations: demential and cancer. “Both are related to inadequate sleep.”
• 10% of adults over 65 suffer from Alzheimer.
• Disruption of deep sleep happens many years before Alzheimer’s disease, “suggesting that it may be an early-warning sign of the condition, or even a contributor to it.”
• Amyloid plaques generate in the brain during Alzheimer. They are poisonous and attack certain parts of the brain, including the central prefrontal lobe, where the waves of deep sleep originate.
• Glymphatic system: “a kind of sewage network” of the brain. It kicks into high gear during sleep.
• “Phrased differently, (…) wakefulness is low-level brain damage, while sleep is neurological sanitation.”
• “Without sufficient sleep, amyloid plaques build up in the brain, especially in deep-sleep-generating regions, attacking and degrading them. The loss of deep NREM sleep cause by this assault therefore lessens the ability to remove amyloid from the brain at night, resulting in greater amyloid deposition.”
• “From this cascaed comes a prediction: getting too little sleep across the adult life span will significantly raise your risk of developing Alzheimer’s disease.”
• Treating sleep disorders in middle and older age adults delayed the onset of Alzheimer’s disease by 5-10 years.
• “No aspect of your health can retreat at the sign of sleep loss and escape unharmed.”
• Shorter sleep, shorter life.
• “This finding impresses how important it is to prioritize sleep in midlife – which is unfortunately the time when family and professional circumstances encourage us to do the exact opposite.”
• Sympathetic nervous system: fight-or-flight. But it can be permanently overactivated by lack of sleep, and this overactivation can be deadly.
• Lack of sleep increases cortisol and shuts off production of growth hormone.
• Daily saving time: the switch in March “results in most people losing an hour of sleep opportunity.” Heart attack rates shasrply increase the next day. In September, the opposite happens. And the same happens with traffic accidents. “Most people think nothing of losing an hour of sleep for a single night, believing it to be trivial and inconsequential. It is anything but.”
• “The less you sleep, the more you are likely to eat. In addition, your body becomes unable to manage those calories effectively, especially the concentrations of sugar in your blood.”
• “far higher rates of type 2 diabetes among individuals that reported sleeping less than six hours a night routinely.”
• Six nights of sleeping 4h per night reduce absorption of glucose by 40%, enough to classify a previously healthy individual as pre-diabetic. This happens because less insulin is produced and also because the insuline sensitivity of cells goes down (more the latter than the former).
• “diabetes lops ten years off an individual’s life expectancy.”
• Two hormones that control appetite: leptin and ghrelin. Leptin: fullness. Ghrelin: hunger. Lack of sleep increases ghrelin and reduces leptin.
• “a sleep deprived body will cry famine in the midst of plenty.”
• Sleep deprived individuals ate 300 calories more each day.
• “sleep loss increases levels of circulating endocannabinoids (…) chemicals produced by the body that are very similar to the drug cannabis.”
• Completely sleep deprived individuals will only spend 147 extra calories in a day compared to those who sleep eight hours. “Sleep, it turns ou t, is an intensely metabolically active state for brain and body alike. For this reason, theories proposing that we sleep to conserve large amounts of energy are no longer entertained.”
• Tiredness makes individuals more sedentary.
• Tired individuals eat more caloric and less healthy foods. The reason is an impaired frontal cortex which normally controls impulses.
• “We ound that a full night of sleep repairs the communication pathway between deep-brain areas that unleash hedonic desires and higher-order brain regions whose job it is to rein in these cravings.”
• Lack of sleep affects the bacteria in the gut (microbiome/enteric nervous system) because of the overdrive of the sympathetic system.
• “the epditemic of insufficient sleep is very likely a key contributor to the epidemic of obesity.”
• “Three-year-olds sleeping just 10.5 hours or less have a 45% increased risk of being obese by age 7 than those who get 12h of sleep a night.”
• With short sleep, caloric deficit tends to be compensated by reducing lean body mass, not fat (70% for sleep deprived vs 50% for non sleep deprived).
• Short sleep reduces testosterone levels significantly.
• “testosterone has a sharpening effect on the brain’s ability to focus.”
• Sleeping less than six hours per night results in a 20% drop in follicular-releasing hormone in women. It also increases the risk of miscarriage in the first trimester.
• Attractiveness is also affected by lack of sleep.
• “The less sleep an individual was getting in the week before facing the active common cold virus, the more likely it was that they would be infected and catch a cold.”
• Sleep also affects the body’s response to the flu vaccine. The same happens with the hepatitis vaccines.
• Natural killer cells are part of the immune system and prevent cancer from growing. Their strength is affected by lack of sleep.
• Sleeping <6 hours per night increases cancer risk by 40%, relative to those sleeping 7 hours or more.
• Cancer employs inflammation as an opportunity to grow and expand through the boxy. Lack of sleep increases inflammation and hence vastly increases the odds of metastasis.
• Lack of sleep distorts genetic expression (some genes get amplified, others get dimmed).
• “Neglect sleep, and you are deciding to perform a genetic-engineering manipulation on yourself each night, tampering with the nucleic alphabet that spells out your daily health story.”
• Part 3
• Dreams: hallucinations, delusions, disorientation, extremee emotional swings, amnesia. “If you were to experience any of these symptoms while awake, you’d be seeking immediate psychological treatment.” But in REM (dreaming), these are all normal and indeed essential processes.
• There’s dreaming on every sleep stage, but very limited (0-20% chance of reporting a dream for someone woken up from the deepest NREM sleep). But vivid dreams only happen in REM sleep.
• “MRI scanners effectively carve up [the brain] into thousands of small, discreet boxes, rather like individual pixels on a screen, and then measure the local activity of [the brain cells] within that specific pixel”
• In deep NREM, “metabolic activity shows a modest decrease” compared to wakefulness. But not during REM. Four regions are up to 30% more active: visuospatial regions at the back of the brain; motor cortex; hippocampus; deep emotional centers (amygdala & cingulate cortex). Other regions show less activity during REM sleep: the cortex (rational thought & impulse control). “REM sleep can therefore be considred as a state characterized by strong activation in visual, motor, emotional, and autobiographical memory regions of the brain, yet a relative deactivation in regions that control rational thought.”
• Nature of dreams can be ascertained by MRI, then by sking the subject what the dream was like.
• The contents of dreams can start to be interpreted by intensive pre-studying of an individual with MRIs, both during wakefulness (by showing images) and while dreaming. Once the data set is collected, the themes of a dream can be predicted.
• This will only evolve in the future, raising ethical issues.
• Freud put dreams squarely in the domain of the brain.
• “Freud believed that dreams came from unconscious wishes that had not been fulfilled.” Dreams were disguised unconscious wishes that could be interpreted.
• His theory, however, was untestable. “A theory that cannot be discerned true or false in this way will always be abandoned by science”
• “journaling your waking thoughts, feelings, and concerns has a proven mental health benefit, and the same appears true of your dreams.”
• “Dreams are not, therefore, a wholesale replay of our waking lives. (…) If there is such a thing as “day residue”, there are but a few drops of the stuff in our otherwise arid dreams.” But not so for emotions, which did carry out much more from the day into the dream.
• “If what you dream about offers no predictive power in determining the benefits of that REM sleep, it would suggest that dreams are epiphenomenal, and REM sleep alone is sufficient.” “Dreams are not the heat of the lightbulb – they are no by-product.”
• Dreams have two functions: 1) nursing emotional and mental health; 2) problem solving and creativity.
• During REM sleep there’s no noradrenaline in the brain.
• Note: adrenaline == epinephrine.
• REM: “this emotional memory reactivation was occurring in a brain free of a key stress chemical.” “a perfectly designed nocturnal soothing balm – one that removes the emotional sharp edges of our daily lives”.
• Theory of overnight therapy: 1) sleeping to remember the details; 2) sleeping to forget the painful/emotional charge from the events. “If true, it would suggest that the dream state supports a form of introspective life review, to therapeutic ends.”
• REM separates the “bitter emotional rind from the 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.”
• “It was not, therefore, time per se that healed all wounds, but instead it was time spent in dream sleep that was providing emotional convalescence.”
• “Cartwright demonstrated that it was only those patients who were expressly dreaming about the painful experiences around the time of the events who went on to gain clinical resolution from their despair, mentally recovering a year later as clinically determined by having no idenitifiable depression. (…) It was only that content-specific form of dreaming that was able to accomplish clinical remission and ofer emotional closure”
• PTSD makes you relive traumatic experiences as if they were happening for the first time. PTSD disrupts REM sleep and increases noradrenaline levels.
• “The theory proposed that a contributing mechanism uderlying the PTSD is the excessively high levels of noradrenaline within the brain that blocks the ability of these patients from entering and maintaining normal REM-sleep dreaming.”
• “The basic scientific theory was no longer in search of clinical confirmation. The two had found each other”
• Prazosin lowers noradrenaline levels in the brain, enhances RE sleep and thus helps PTSD patients recover.
• REM sleep fine tunes the areas of the brain responsible for reading and interpreting facial expressions.
• When sleep deprived, the brain has a fear bias.
• “Now think of occupations that require individuals to be sleep-deprived, such as law enforcement and military personnel, doctors, nurses, and those in the emergency services—not to mention the ultimate caretaking job: new parents.”
• “Without REM sleep and its ability to reset the brain’s emotional compass, those same individuals will be inaccurate in their social and emotional comprehension of the world around them, leading to inappropriate decisions and actions that may have grave consequences.”
• “But come the early teenage years and the inflection point of parental independence wherein an adolescent must navigate the socioemotional world for himself, now we see the young brain feasting on this emotional recalibration benefit of REM sleep.”
• “Aside from being a stoic sentinel that guards your sanity and emotional well-being, REM sleep and the act of dreaming have another distinct benefit: intelligent information processing that inspires creativity and promotes problem solving. So much so, that some individuals try controlling this normally non-volitional process and direct their own dream experiences while dreaming.”
• “REM sleep is informational alchemy.”
• “I saw in a dream a table where all the elements fell into place as required. Awakening, I immediately wrote it down on a piece of paper. Only in one place did a correction later seem necessary.” — Mendeleev on the periodic table of elements
• The dramatic alterations in brain activity during NREM and REM sleep, and their tidal shifts in neurochemical concentrations, do not reverse instantaneously when you awaken. Instead, the neural and chemical properties of that particular sleep stage will linger, creating the inertia period that separates true wakefulness from sleep, and last some minutes.”
• “By restricting the length of whatever cognitive test we performed to just ninety seconds, we felt we could wake individuals up and very quickly test them in this transitional sleep phase. In doing so, we could perhaps capture some of the functional properties of the sleep stage from which the participant was woken, like capturing the vapors of an evaporating substance and analyzing those vapors to draw conclusions about the properties of the substance itself.”
• “Overall, problem-solving abilities rocketed up, with participants solving 15 to 35 percent more puzzles when emerging from REM sleep compared with awakenings from NREM sleep or during daytime waking performance!”
• “The solutions simply “popped out” following awakenings from REM sleep”
• “The lingering vapors of REM sleep were providing a more fluid, divergent, “open-minded” state of information processing.”
• “Instead, the REM-sleep brain was shortcutting the obvious links and favoring very distantly related concepts. The logic guards had left the REM-sleep dreaming brain.”
• “Our human memories are, on the other hand, richly interconnected in webs of associations that lead to flexible, predictive powers. We have REM sleep and the act of dreaming, to thank for much of that inventive hard work.”
• “REM sleep is capable of creating abstract overarching knowledge and super-ordinate concepts out of sets of information.”
• “Rather, the dream algorithm was cherry-picking salient fragments of the prior learning experience, and then attempting to place those new experiences within the back catalog of preexisting knowledge.”
• “Different from solidifying memories, which we now realize to be the job of NREM sleep, REM sleep, and the act of dreaming, takes that which we have learned in one experience setting and seeks to apply it to others stored in memory.”
• Note: analogy then happens in REM!
• “Scientists had gained objective, brain-based proof that lucid dreamers can control when and what they dream while they are dreaming.”
• Part 4
• Sonambulism: movement while asleep. It happens during NREM. State of mixed consciousness. The brain reading looks like NREM, despite the activity.
• Sleepwalking happens more often in children and most episodes are harmless and do not require intervention.
• “Being sleep deprived is not insomnia.” Sleep deprivation is “1) having the adequate ability to sleep; yet 2) giving oneself an inadequate opportunity to sleep”
• Insomnia: inadequate ability to generate sleep despite allowing oneself the adequate opportunity to get sleep. Enough opportunity: 7-9 hours.
• Paradoxical insomnia: believing you sleep badly when you actually do not.
• Types of insomnia: sleep onset insomnia (falling asleep); maintenance insomnia (difficulty staying asleep).
• “The emphasis on duration of the sleep problem (more than three nights a week, for more than three months) is important. All of us will experience difficulty sleeping every now and then, which may last just one night or several. That is normal.”
• 1/9 of the population “will meet the strict clinical criteria for insomnia”. It is twice as common in women than in men.
• “insomnia is on of the most pressing and prevalent medical issues facing modern society”
• Most common triggers of insomnia: emotional concerns and emotional distress.
• Overstimulation of the sympathetic nervous system induces insomnia by raising body core temperature and increasing concentrations of cortisol, adrenaline and noradrenaline. Also, for insmniac patients, emotion generating regions and memory-recollection centers remained active throughout sleep.
• “Simply put, the insmnia patients could not disengage from a pattern of altering, worrisome, ruminative brain activity.”
• “Real optimism is to be found in these new, non-drug therapies that I urge you to explore should you suffer from true insomnia.”
• Narcolepsy: “Emotionless, you will simply exist, rather than live. Tragically, this is the very kind of reality many narcoleptic patients are forced to adopt”
• Narcolepsy usually emerges between ages 10-20. It also happens in other mammal species. Symptoms: “1) excessive daytime sleepiness; 2) sleep paralysis; 3) cataplexy”. Narcoleptic sleep attack is equivalent to sleepiness equivalent to being awake for 3-4 days.
• “Don’t worry if you have had an episode of sleep paralysis at some piont in your life. (…) Narcoleptic patients, will, however, experience sleep paralysis far more frequently and severely than healthy individuals.”
• Cataplexy: total body collapse, usually triggered by strong emotions, positive or negative, while maintaining consciousness.
• The hypothalamus is where the brain has the on/off switch for sleep (sleep-wake switch). It is close to the circadian clock. “Like an electrical light switch, it can flip the power on (wake) or off (sleep).” Neurotransmitter for this function: orexin. In narcoleptics, the switch is stuck between on and off.
• Note: it requires a chemical (orexin) to keep us awake. This subtly supports the notion that slumber is the original state.
• “While we have effective interventions for other sleep disorders, such as insomnia nd sleep apnea, we lag far behind the curve for treating narcolepsy. (…) Overall, the treatment outlook for narcoleptic patients is bleak at present, and there is no cure in sight.”
• Orexin blockers are being researched as a way to induce sleep.
• Fatal familial insomnia: triggered by a prion protein caused by a genetic defect. Life expectancy after diagnosis is 10 months. “FFI is still the strongest evidence we have that a lack of sleep will kill a human being.”
• On average, rats will die after 15 days without sleep. “Two additional results quickly followed. First, death ensued as quickly from total sleep deprivation as it did from total food deprivation. Second, rats lost their lives almost as quickly from selective REM-sleep deprivation as they did following total sleep deprivation. total absence of NREM sleep still proved fatal, it just took longer to inflict the same mortal consequence – 45 days, on average.”
• Loss of body mass, loss of temperature regulation, despite higher intake of calories.
• “if you impose a total basence of sleep on an organism (…) it indeed becomes an emergency, and you will find the biological equivalent of this shattered glass strewn throughout the brain and the body, to fatal effect.”
• “The problem is that some people confuse time slept with sleep opportunity time.”
• The uptick in death risk for those sleeping 9 hours or more could be a ma tter of correlation, since already sick individuals need to recover. “no biological mechanisms that show sleep to be in any way harmful have been discovered.”
• Factors decreasing sleep in modern life: 1) constant electric & LED light; 2) regularized temperature; 3) caffeine; 4) alcohol; 5) “a legacy of punching time cards”.
• “Humans are predominantly visual creatures. More than a third of our brain is devoted to processing visual information, far exceeding that given over to sounds or smells, or those supporting language and movement. For early Homo sapiens, most of our activities would have ceased after the sun set.”
• Firelight had little impact on our sleep-wake patterns. Not so with gas and oil burning lamps. But the tipping point was electric light. That happened in the mid-1870s with Edison Electric.
• “Sunlight contains a powerful blend of all of these colors (…). The loss of daylight inorms our suprachiasmatic nucleus that nighttime is now in session (…) Appropriately scheduled tiredness, followed by sleep, would normally occur several hours after dusk across our human collective.”
• “Artificial evening light, even that of modest strength, or lux, will fool your suprachiasmatic nucleus into believing the sun has not yet set.”
• “The degree to which evening electric light winds back your internal twenty-four-hour clock is important: usually two to three hours each evening, on average.”
• “By delaying the release of melatonin, artificial evening light makes it considerably less likely that you’ll be able to fall asleep at a reasonable time.”
• As little as 8-10 lux can delay melatonin release.
• Blue LED lights have an even geater impact on us than incandescent lights. “The light receptors in the eye that communicate “daytime” to the suprachiasmatic nucleus are most sensitive to short-wavelength light within the blue spectrum – the exact sweet spot where blue LEDs are most powerful.” The impact is twice as much as with incandescent, at the same lux level.
• Reading at night on a device with LED compared to reading a book supressed melatonin release by over 50%. Individuals exposed to LED had less REM sleep, felt less rested and they had a 90 minute lag in their evening rising melatonin levels the next day.
• Remedies: dim lights at night, limit device use, use red filters for devices, blackout curtains at night.
• Alcohol is a sedative. “The answer comes down to the fact that your increased sociability is caused by sedation of one part of your brain, the prefrontal cortex, early in the timeline of alcohol’s creeping effects.”
• “Give alcohol a little more time, and it begins to sedate other parts of the brain”
• “sedation is not sleep. Alcohol sedates you out of wakefulness, but it does not induce natural sleep. THe electrical brainwave state you enter via alcohol is not that of natural sleep; rather, it is akin to a light form of anesthesia.”
• Alcohol fragments sleep; by it being less continuous, it is not as restorative. Alcohol also “is one of the most powerful suppressors of REM sleep that we know of. When the body metabolizes alcohol it produces by-product chemicals called aldeydes and ketones. The aldehydes in particular will block the brain’s ability to generate REM sleep.”
• “People consuming even moderate amounts of alcohol in the afternoon and/or evening are thus depriving themselves of dream sleep.”
• “Should the addict enter a rehabilitation program and abstain from alcohol, the brain will begin feasting on REM sleep, binging in a desperate effort to recover that which is has been long starved of – an effect called the REM-sleep rebound.”
• “those who had their sleep laced with alcohol on the first night after learning suffered what can conservatively be described as partial amnesia seven days later, forgetting more than 50% of all that original knowledge.”
• “More surprising, perhaps, was the realization that the brain is not done processing that knowledge after the first night of sleep. Memories remain perilously vulnerable to any disruption of sleep (including that from alcohol) even up to three nights after learning”
• “Nightly alcohol will disrupt your sleep, and the annoying advice of abstiencne is the best, and most honest, I can offer.”
• “Thermal environment (…) is perhaps the most underappreciated factor determining the ease with which you will fall asleep tonight, and the quality of sleep you will obtain.”
• “It is ambient room temperature that has suffered a dramatic assault from modernity.”
• Core temperature needs to decrease by 1C to successfully initiate sleep. For that reason, a room that’s a bit too cold helps sleep.
• “Your nocturnal melatonin levels are therefore controlled not only by the loss of daylight at dusk, but also the drop in temperature that coincides with the setting sun.”
• The body cools itself through the hands, feet and head.
• “Homo sapiens (and thus modern sleep patterns) evolved in eastern equatorial regions of Africa. Despite experiencing only modest fluctuations in average temperature across a year (+/- 3C), these areas have larger temperature differentials across a day and night in both the winter (+/- 8C) and the summer (+/- 7C).
• Average ideal temperature for sleep: 18.3C.
• Hot baths allow for cooling off the core. “HOt baths prior to bed can also induce 10 to 15 percent more deep NREM sleep in healthy adults.”
• “No other species demonstrates this unnatural act of prematurely and artificially terminating sleep”
• “Participants artificially wrenched from sleep will suffer a spike in blood pressure and a shock acceleration in heart rate cuased by an explosive burst of activity from the fight-or-flight branch of the nervous system.” This is made much worse by snoozing and re-awakening.
• “Waking up at the same time of day, every day, no matter if it is the week or weekend is a good recommendation for maintaining a stable sleep schedule if you are having difficulty with sleep.”
• “Sleeping pills do not provide natural sleep, can damage health, and increase the risk of lie-threatening diseases.”
• “No past or current sleeping medications on the legal (or illegal) market induce natural sleep.”
• “Sleeping pills, old and new, target the same system in the brain that alcohol does (…) and are thus part of the same general class of drugs: sedatives.”
• “The electrical type of “sleep” these drugs produce is lacking in the largest, deepest brainwaves.”
• “In other words, there was no objective benefit of these sleeping pills beyond that which a placebo offered.”
• Sleeping pills may cause issues with brain wiring during sleep, as well as cancer.
• “individuals taking sleeping pills were significantly more likely to die across the study periods (usually a handful of years) than those who were not”
• In a controlled comparison, “Those taking sleeping pills were 4.6 times more likely to die over this short two-and-a-half-year period thatn those who were not using sleeping pills.”
• “even very occasional users – those defined as taking just eighteen pills per year – were still 3.6 times more likely to die at some point cross the assessment window than non-users.”
• Causes for this: higher rates of infection, perhaps because of poor sleep quality. Increased risk for fatal car accidents. Higher risk for falls at night. Also higher rates of heart disease and stroke. Also cancer. It is not clear whether pills cause cancer or not, but the correlation is high.
• “Ironically, such a trial may never be conducted, since a board of ethics may deem the already apparent death hazard and carcinogenic risks associted with sleeping pills to be too high.”
• “In my scientific, though non-medical, opinion, I believe that the existing evidence warrants far more transparent medical education of any patient who is considering taking a sleeping pill, at the very least.”
• “If such a drug – one with sound scientific data demons trating benefits that far outweight any health risks – is ultimately developed, I would support it. It is simply that no such medication currently exists.”
• Cognitive behavioral therapy (CBT) is the most effective non-pharmacological method for improving sleep: sleep hygiene, regular bedtime and wake-up, go to bed only when sleepy and avoid catnapping, never lie awake in bed for a significant time period, avoid daytime napping, reduce anxiety-provoking thoughs and worries, remove visible clockfaces rom view in the bedroom.
• CBT is more effective than sleeping pills in clinical trials and is recommended as the first-line treatment for chronic insomnia.
• Most important sleep hygiene advice: go to bed and wake up at the same time of day no matter what.
• “It is still a clear bidirectional relationship, however, with a significant trend toward increasing better sleep with increasing levels of physical activity., and a strong influence of sleep on daytime physical activity.”
• Work out no later than 2-3 hours before going to bed.
• “Severe caloric restriction, such as reducing food intake to just 8000 calories a day for one month, makes it harder to fall asleep normally, and decreases the amount of deep NREM sleep at night.”
• Food has an impact on type and quality of sleep but results are still inconclusive.
• “Deep currents of sleep neglect circulte throughout all developed nations”
• “Sleep deprivation degrades many of the key faculties required for most of employment.”
• “Individuals who sleep fewer than seven hours a night on average cause a staggering fiscual cost to their country”
• “Insufficient sleep robs most nations of more than 2% of thei rGDP”
• “shoter sleep amounts predict lower work rate and slow completion speed of basic tasks.”
• “you find that those individuals who obtained less sleep in the preceding days are the same people who consistently select less challenging problems. THey opt for the easy way out, generating fewer creative solutions in the process.”
• “Why try to boil a pot of water on medium heat when you could do so in half the time on high?”
• “They seemed unaware of their poorer work effort and performance (…) Even the simplest daily routines (…) have been found to decrease following a night of sleep loss.”
• Sleep loss also increases unethical behavior, due to a depression in frontal cortex activity.
• “employees who sleep six hours or less are significantly more deviant and more likely to lie the following day than those who sleep six hours or more.”
• “Differences in individual leadership performance fluctuate dramatically from one day to the next”
• Underslept supervisors can negatively affect morale of their employees.
• “Allowing and encouraging employees, supervisors, and executivs to arrive at work well rested turns them from simply looking busy yet ineffective, to being productive, honest, useful individuals who inspire, support, and help each other. Ounces of slep offer pounds of business in return.”
• In a study, an extra hour of sleep represented 4-5% larger wages.
• NASA has a nap culture, given the large measurable increase in performance naps induce on astronauts.
• “many modern-day torture methods are deviously designed to leave no evidence of physical assault.” Amongst them, sleep deprivation.
• “I came across prisoners who signed what they were ordered to sign, only to get what their interrogator promised them. He did not promise them their liberty. He promised them – if they signed – uninterrupted sleep.” — Menachem Begin
• US still allows for 24 hour interrogations.
• 50% of US high schools begin before 720am, 80% of them start before 815am.
• “unnecessarily bankrupting the sleep of a teenager could make all the difference in the precarious tipping point between psychological wellness and lifelong psychiatric illness. This is a strong statement, and I do not write it flippantly or without evidence.”
• “REM sleep is what stands between rationality and insanity.”
• “A century ago, schools in the US started at 9am. As a result, 95% of all children woke up without an alarm clock.”
• “the longer a child slept, the more intellectually gifted they were.”
• “if sleep really is so rudimentary to learning, then increasing sleep time by delaying start times should prove transformative. It has.”
• “It is clear that a tired, under-slept brain is little more than a leaky memory sieve, in no state to receive, absorb, or efficiently retain an education.”
• Children from low-income families rely on school buses and have to wake up earlier, losing more sleep.
• “Research findings have also revealed that incresing sleep by way of delayed school start times wonderfully increases class attendance, reduces behavioral and psychological problems, and decreases substance and alcohol use.” It also makes school finish later and keeps adolescents more shielded from the harm of the “well-researched “danger window” between 3 and six pm, when schools finish but before parents return home.”
• More sleep in teenagers vastly reduced their involvement in traffic accidents, which is their leading mortality cause. Reductions were in the order of 50-70%; to compare, ABS breaking reduces accident rates by 20-25%.
• Kids 5-18 ae sleeping two few hours now than a century ago.
• Link between sleep deprivation and ADHD.
• ADHD medications are stimulants that prevent sleep.
• “we seem to have no problem at all in allowing pharmaceutical comapnies to broadcast prime-time commercials highlighting ADHD and promoting the sale of amphetamine-based drugs.”
• “we estimate that more than 50% of all chilren with an ADHD diagnosis actually have a sleep disorder”
• Parents are generally unaware of the lack of sleep of their kids.
• Sleep levels strongly influence rates of medical error.
• The grueling residency hours of doctors in the US come from the personal practices of a doctor addicted to cocaine.
• 30 hour shifts increase serious medical errors by 36%. After 30 a hour shift without sleep, diagnostic mistakes increase by 460%. “one in five medical residents will make a sleepless-related medical error that causes significant, liable harm to a patient. One in twenty residents will kill a patient due to a lack of sleep.”
• “Medical errors are the third-leading cause of death among Americans after heart attacks and cancer.”
• Medical residents are more likely to be involved in serious car crashes at the end of their shifts.
• “If you are about to undergo an elective surgery, you should ask how much sleep your doctor has had and, if it is not to your liking, you may not want to proceed.”
• “No amount of years on the job helps a doctor “learn” how to overcome a lack of sleep and develop resilience.”
• “after twenty-two hours without sleep, human performance is impaired to the same level as that of someone who is legally drunk.”
• “Why haven’t these [findings]s triggered a responsible revision of work schedules for residents and attending physicians (…)?
• New limits on first-year US residents are still grueling: 1) maximum 80-hour work week; 2) work no more than 24 hours nonstop; 3) perform one overnight on call shift every third night. “That revised schedule still far exceeds any ability of the brain to perform optimally.” And these changes haven’t been applied (yet) to residents on the second year and beyond.
• “There’s simply no evidence-based argument for persisting with the current sleep-anemic model of medical training”
• “we s a society must work toward dismantling our negative and counterproductive attitude toward sleep”
• Sleep deprivation was a cause in both the Chernobyl and Exxon Valdez disasters.
• “Accepting that our lack of sleep is a slow form of self-euthanasia, what can be done about it?”
• “First, we must understand why the problem of deficient sleep seems to be so resistant to change ( …) Second, we must develop a structured model for effecting change at every possible leverage point we can identify.”
• Technology should be embraced, not fought. “Two exciting possibilities unfold. First, such devices could compare the sleep of each family member in each separate bedroom with the temperature sensed in each room by the thermostat. Using common machine-learning algorithms applied over time, we should be able to intelligently teach the home thermostat what the thermal sweet spot is for each occupant in each bedroom (…) (perhaps slpitting the difference when there are two or more individuals per room). (…) Better still, we could program a natural circadian lull and rise in tempreature across the night that is in harmony with each body’s expectations”
• “The second passive solution concerns electric light. (…) Soon, we should be able to engineer LED bulbs with filters that can vary the wavelength of light that they emit (…) The lightbulbs (and even other networked LED-screen devices, such as iPads) would be instructed to gradually dial down the harmful blue light in the home as the evening progresses, based on an individual’s (…) natural sleep-wake pattern. (…) Come the morning, we can reverse this trick. We can now saturate our indoor environments with powerful blue light that shuts off any lingering melatonin.”
• “What if car cockpits could be bathed in blue light during early-morning commutes?”
• “Solutions that are less passive, requiring an individual to actively participate in change, wil be harder to institute.”
• Data helps institute and maintain healthy habits.
• Predictalytics: see the impact of an action today in your future. “Men could see projections on how much their testicles wlil shrink or their testosterone level will drop should their sleep neglect continue.”
• There’s virtually no educational materials about sleep in schools. “Generation after generation, our young minds continue to remain unaware of the immediate dangers and protracted health impacts of insufficient sleep”
• “a longer health span, absolved of the mid- and late-life diseases and disorders that we know are caused by (and not simply associated with) chronic short sleep.”
• Aetna gives bonuses to employees for getting more sleep. The author suggests giving more vacation time as well.
• “As we have learned, sleep continuity – consistently getting seven to nine hours of sleep opportunity each night, every night, without running a debt during the week and hoping to pay it off by binge-sleeping at the weekend – is just as important as total sleep time”
• Besides bonuses, flexible work shifts.
• Lack of sleep increases pain sensitivity. “sleep appears to be a natural analgesic”
• “we should be able to reduce the dose of narcotic drugs on our hospital wards by improving sleep conditions.” How to do this in hospitals: remove unnecessary alarms & equipment, make the staff aware of the importance of sound sleep, and schedule tests for patients according to their habitual sleep-wake rhythms. Finally: earplugs, face mask and dim lighting.
• The health impact of proper lighting on neonatal units can be huge.
• Prosecutorial law against drowsy driving could be possible in the future, with technology that can prove lack of slep.
• “This silent sleep loss epidemic is the greatest public health challenge we face n the twenty-first century in developed nations.”
• “I believe it is time for us to reclaim our right to a full night of sleep, without embarrassment or the damaging stigma of laziness. (…) Then we may remember what if feels like to be truly awake during the day, infused with the very deepest plenitude of being.”