Thread by @ReformedTrader

1/ Why We Sleep (Matthew Walker)

"There does not seem to be one major organ within the body or process within the brain that isn’t optimally enhanced by sleep (and detrimentally impaired when we don’t get enough)." (p. 6)

amazon.com/Why-We-Sleep-U…

2/ "The physical and mental impairments caused by one night of bad sleep dwarf those caused by an equivalent absence of food or exercise.

"Routinely sleeping less than six hours a night weakens your immune system, substantially increasing your risk of certain forms of cancer.

3/ "It is be linked to your risk of developing Alzheimer’s.

"Inadequate sleep—even moderate reductions for just one week—disrupts blood sugar levels so profoundly that you would be classified as pre-diabetic.

4/ "It increases the likelihood of your coronary arteries becoming blocked and brittle, setting you on a path toward cardiovascular disease, stroke, and congestive heart failure.

"It contributes to all major psychiatric conditions, including depression, anxiety, and suicidality.

5/ "It increases a hormone that makes you feel hungry while suppressing a one that would signal fullness.

"Dieting without enough sleep is futile: most of the weight lost comes from lean mass, not fat.

"Drowsy driving causes hundreds of thousands of accidents each year." (p. 3)

6/ "Unlike morning larks, night owls are frequently incapable of falling asleep early at night, no matter how hard they try. It is only in the early-morning hours that owls can drift off. Having not fallen asleep until late, owls of course strongly dislike waking up early.

7/ "When a night owl is forced to wake up too early, her prefrontal cortex remains in a disabled, “offline” state.

"An adult’s owlness or larkness, also known as their chronotype, is strongly determined by genetics." (p. 18)

8/ "Melatonin provides the official instruction to commence the event of sleep but does not participate in the sleep race itself. For these reasons, melatonin is not a powerful sleeping aid in and of itself, at least not for healthy, non-jet-lagged individuals.

9/ "That said, the placebo effect should not be underestimated.

"With dawn, as sunlight enters the brain through the eyes (even through the closed lids), a brake pedal is applied to the pineal gland, thereby shutting off the release of melatonin." (p. 21)

10/ "When adenosine concentrations peak, an irresistible urge for slumber takes hold. It happens to most people after 12-16 hours of being awake.

"Caffeine blocks the sleepiness signal normally communicated by adenosine. Caffeine has an average half-life of 5-7 hours." (p. 26)

11/ "Could you fall back asleep at ten or eleven a.m.? If so, you are likely not getting sufficient sleep quantity and/or quality.

"Can you function optimally without caffeine before noon? If not, you are most likely self-medicating your state of chronic sleep deprivation.

12/ "If you didn’t set an alarm clock, would you sleep past that time? (If so, you need more sleep than you are giving yourself.) Do you find yourself at your computer screen reading and rereading the same sentence? (This is often a sign of a fatigued, under-slept brain.)" (p.34)

13/ "Think of the wake state as reception (learning), NREM sleep as reflection (moving raw skills to long-term memory), and REM sleep as integration (interconnecting raw skills with each other, with past experiences, and building innovative problem-solving abilities)." (p. 52)

14/ "The true pattern of biphasic sleep—for which there is anthropological, biological, and genetic evidence, and which remains measurable in all human beings to date—is one consisting of a longer bout of continuous sleep at night, followed by a shorter midafternoon nap." (p. 69)

15/ "None of the individuals had a history of coronary heart disease or stroke at the start of the study. However, those that abandoned regular siestas suffered a 37% increased risk of death from heart disease across the 6-year period relative to those with regular daytime naps.

16/ "The effect was especially strong in workingmen, where the ensuing mortality risk of not napping increased by well over 60%." (p. 69)

17/ "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.

18/ "NREM sleep helps transfer and make safe newly learned information into long-term storage sites of the brain. But it is REM sleep that takes these freshly minted memories and begins colliding them with the entire back catalog of your life’s autobiography.

19/ "These mnemonic collisions during REM sleep spark creative insights as novel links are forged between unrelated pieces of information.

"We can awake the next morning with new solutions to previously intractable problems or be infused with radically original ideas." (p. 73)

20/ "Depriving the infant rats of REM sleep stalled construction of their cerebral cortex.

"When the infant rat pups were finally allowed to get some REM sleep, assembly of the cerebral rooftop did restart, but it didn’t accelerate, nor did it ever fully get back on track.

21/ "Rats deprived of REM sleep during infancy go on to become socially withdrawn and isolated as adolescents and adults.

"Alcohol is one of the most powerful suppressors of REM sleep that we know of (and readily crosses the placental barrier)." (p. 80)

22/ "Administering caffeine to juvenile rats disrupts deep NREM sleep and delay numerous measures of brain maturation and the development of social activity, independent grooming, and the exploration of the environment—measures of self-motivated learning." (p. 90)

23/ "Children become sleepy earlier and wake up earlier than their parents.

"In contrast, by the time parents are getting tired, as their circadian rhythms take a downturn and melatonin release instructs sleep—perhaps 10-11 p.m.—a teenager can still be wide awake." (p. 90)

24/ "The older we get, the more frequently we wake up at night. Causes include interacting medications and diseases, but chief among them is a weakened bladder.

"An older individual is at risk of falling and breaking bones during nighttime visits to the bathroom." (p. 95)

25/ "Unlike young or middle-age adults, where melatonin has not proved efficacious for helping sleep beyond jet lag, prescription melatonin has helped boost the elderly, reducing time taken to fall asleep and improving self-reported sleep quality and morning alertness." (p. 99)

26/ "Seniors are unable to generate sleep spindles to the same degree as young, healthy adults (40% deficit).

"The fewer the number of spindles an elderly brain produced on a particular night, the lower the learning capacity of that older individual the next day." (p. 110)

27/ "Even daytime naps as short as twenty minutes can offer a memory consolidation advantage, so long as they contain enough NREM sleep." (p. 115)

28/ "Using sound cuing (“meow” for a cat picture or “ding-a-ling” for a bell picture), we cherry-pick specific slices of your autobiographical past and preferentially strengthen them by using the individualized sound cues during sleep." (p. 120)

29/ "Sleep powerfully, yet selectively, boosted the retention of those words previously tagged for “remembering,” yet actively avoided the strengthening of memories tagged for “forgetting.” Participants who did not sleep showed no such differential saving of memories." (p. 121)

30/ "Post-performance sleep accelerates physical recovery from common inflammation, stimulates muscle repair, and helps restock cellular energy in the form of glucose and glycogen." (p. 130)

31/ "A two-second exhaustion-driven microsleep at 30 mph with a modest angle of drift can result in your vehicle transitioning entirely from one lane to the next. This includes into oncoming traffic. Should this happen at 60 mph, it may be the last microsleep you have." (p. 134)

32/ "Ten days of six hours of sleep a night was all it took to become as impaired in performance as going without sleep for 24 hours straight (and showed no signs of leveling out). The performance deterioration might have continued to build up over weeks or months." (p. 136)

33/ "When participants were asked about their subjective sense of how impaired they were, they consistently underestimated their degree of performance disability.

"Drive after four hours or less of sleep, and you are 11.5 times more likely to be involved in an accident." (p.139)

34/ "Power naps or caffeine may momentarily increase basic concentration under conditions of sleep deprivation.

"Neither one can salvage more complex functions of the brain, including learning, memory, emotional stability, complex reasoning, or decision-making." (p. 143)

35/ "Insufficient sleep also determines relapse rates in numerous addiction disorders, associated with reward cravings that are unmetered, lacking control from the rational head office of the brain’s prefrontal cortex." (p. 148)

36/ "Simply disrupting the depth of an individual’s NREM sleep with infrequent sounds, preventing deep sleep and keeping the brain in shallow sleep without actually waking the individual up will produce similar brain deficits and learning impairments." (p. 153)

37/ "Inadequate sleep and Alzheimer’s disease interact in a vicious cycle. Without sufficient sleep, amyloid plaques build up, especially in deep-sleep-generating regions. The loss of deep NREM sleep caused by this assault further lessens the ability to remove amyloid." (p. 161)

38/ "One night of modest sleep reduction—even just one or two hours—will promptly speed the contracting rate of a person’s heart, hour upon hour, and significantly increase the systolic blood pressure. The body can remain stuck in some degree of fight-or-flight state." (p. 165)

39/ "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.

40/ "Eye disease that can end in blindness, nerve disease that commonly results in amputations, and kidney failure necessitating dialysis or transplant are all consequences of prolonged high blood sugar, as are hypertension and heart disease." (p. 170)

41/ "Individuals were more ravenous when sleeping 4-5 hours a night, despite being given the same amount of food and being similarly active.

"Cravings for sweets, bread and pasta, and salty snacks increased by 30-40% when sleep was reduced by several hours each night." (p. 171)

42/ "Lack of sleep triggers an excess of circulating cortisol that cultivates “bad bacteria” to fester throughout your microbiome. As a result, insufficient sleep will prevent the meaningful absorption of all food nutrients and cause gastrointestinal problems." (p. 177)

43/ "Limiting lean, healthy young males in their mid-twenties to five hours of sleep for one week effectively “ages” them by ten to fifteen years in terms of testosterone virility." (p. 179)

44/ "Faces pictured after one night of short sleep were rated as looking more fatigued, less healthy, and significantly less attractive, compared with the appealing image of that same individual after they had slept a full eight hours." (p. 181)

45/ "Participants who obtained 7-9 hours’ sleep the week before getting the flu shot generated a powerful antibody reaction. Those in the sleep-restricted group produced less than 50% of that immune reaction. Similar consequences have been reported for hepatitis A and B vaccines.

46/ "Even if an individual is allowed two or even three weeks of recovery sleep to get over the assault of one week of short sleeping, she never goes on to develop a full immune reaction to the flue shot." (p. 183)

47/ "Examining healthy young men and controlling for spurious factors, such as physical activity, Irwin found that a single night of 4 hours of sleep swept away 70% of natural cancer-fighting killer cells circulating in the immune system relative to full 8 hours of sleep.

48/ "Some cancer cells lure inflammatory factors into the tumor mass to help initiate the growth of blood vessels that bring more nutrients and oxygen. Tumors can also use inflammatory factors to further damage and mutate DNA.

49/ "Inflammation may also help physically shear some of the tumor from its local moorings, allowing the cancer to spread to other parts of the body.

"Sleep-deprived mice suffered a 200% increase in the speed and size of cancer growth, relative to the well-rested group." (p.184)

50/ "35-55% percent of emotional themes and concerns that participants were having while they were awake during the day powerfully and unambiguously resurfaced in the dreams they were having at night." (p. 204)

51/ "With the absence of such emotional acuity, normally gifted by the re-tuning skills of REM sleep at night, the sleep-deprived participants slipped into a default of fear bias, believing even gentle- or somewhat friendly looking faces were menacing." (p. 216)

52/ "While we do not yet fully understand the cause of somnambulism episodes, existing evidence suggests that an unexpected spike in nervous system activity during deep sleep is one trigger. The brain gets stuck somewhere in between deep NREM sleep and wakefulness.

53/ "The individual is in a state of mixed consciousness—neither awake nor asleep. The brain performs basic but well-rehearsed actions, such as walking over to a closet and opening it, placing a glass of water to the lips, or uttering a few words or sentences." (p. 238)

54/ "The two most common triggers of chronic insomnia are psychological: (1) emotional concerns/worry, and (2) emotional distress/anxiety. One of the few times that we inwardly reflect is when our heads hit the pillow, but is no worse time to consciously do this." (p. 243)

55/ "iPad reading delayed the rise of melatonin by up to three hours relative to the natural rise in these same individuals when reading a printed book.

"Individuals had less REM sleep following iPad reading and felt sleepier throughout the day following iPad use at night.

56/ "Participants suffering a ninety-minute lag in their evening rising melatonin levels for several days after iPad use ceased.

"Alcohol fragments sleep, littering the night with brief awakenings. Alcohol-infused sleep is therefore not continuous and not restorative.

57/ "Unfortunately, most of these nighttime awakenings go unnoticed by the sleeper since they don’t remember them.

"People consuming even moderate amounts of alcohol in the afternoon and/or evening can inadvertently deprive themselves of REM sleep." (p. 271)

58/ "Memories remain vulnerable to disruption of sleep (including that from alcohol) even up to three nights after learning, despite two full nights of natural sleep prior." (p. 274)

59/ "Selectively warming feet and hands by 1°F caused a local swell of blood to these regions, charming heat out of the body’s core. This allowed participants to fall asleep 20% faster than usual, even though these were already young, healthy, fast-sleeping individuals." (p. 278)

60/ "A hot bath invites blood to your skin. When you get out, dilated vessels on the surface help radiate out inner heat, your core temperature plummets, and you fall asleep more quickly. Hot baths prior to bed can induce 10-15% more deep NREM sleep in healthy adults." (p. 279)

61/ "Participants artificially awakened from sleep can experience a spike in blood pressure and an acceleration in heart rate.

"The snooze feature means that you will repeatedly impose that cardiovascular spike again and again within a short span of time." (p. 279)

62/ "Both the placebo and the sleeping pills reduced the time it took to fall asleep (10-30 min), but the change was not statistically different.

"Natural sleep solidified memory connections within the brain in the placebo condition formed during the initial learning phase.

63/ "Ambien-induced sleep not only failed to match these benefits (despite the animals sleeping just as long) but also caused a 50% weakening (unwiring) of the brain-cell connections originally formed during learning. Ambien-laced sleep became a memory eraser." (p. 284)

64/ Instead of sleeping pills, "reduce caffeine and alcohol intake, remove screen technology from the bedroom, and keep a cool bedroom.

"Establish a regular bedtime and wake-up time, even on weekends; go to bed only when sleepy and avoid sleeping on the couch early/mid-evenings.

65/ "Never lie awake for long; do something relaxing until the urge to sleep returns. Avoid daytime napping if you have difficulty sleeping at night. Reduce worry by learning to mentally decelerate before bed. Remove clockfaces to prevent clock-watching anxiety at night." (p.290)

66/ "Regular exercise to help maintain the quantity and quality of sleep. Sleep, in return, boosts fitness and energy.

"But try not to exercise right before bed, as body temperature can remain high for an hour or two after physical exertion.

67/ "Avoid going to bed too full or too hungry, and shy away from diets that are excessively biased toward carbohydrates (greater than 70% of all energy intake), especially sugar." (p. 295)

68/ "Insufficient sleep cost $2,000 per employee per year in lost productivity ($3,500 in those suffering the most serious lack of sleep). It costs most nations more than 2% of GDP—the entire cost of each country’s military and almost as much as is spent on education." (p. 297)

69/ "Individuals who obtained less sleep consistently select less challenging problems to solve (using each person as her own baseline control).

"People seemed unaware of their poorer work effort and performance—a theme of subjective misperception of ability when sleep-deprived.

70/ "Differences in individual leadership performance fluctuate dramatically from one day to the next, and the size of that difference far exceeds the average difference from one individual leader to another. The amount of sleep leaders get may be a factor." (p. 300)