WHY WE SLEEP 2 7 ー TURNING DOWN THE NIGHTCAP—ALCOHOL Short ofprescription sleeping pills, the most misunderstood ofall"sleep aids" is C0h01. Many individuals believe alcohol helps them to fall asleep more easily, or even Offers sounder sleep throughout the night. BOth are resolutely untrue. Alcoh01 is in a class of drugs called sedatives. lt binds to recep- tors within the brain that prevent neurons 仕 om firing their electri- cal impulses. Saying that C0h01 is a sedative 0ften confuses people, as alcohol ⅲ moderate doses helps individuals liven up and become more SOCial. HOW can a sedative enliven you? The answer comes down tO the fact that your increased sociability is caused by sedation Of one part 0f your brain, the prefrontal cortex, early ⅲ the timeline of alco- hol's creeping effects. As we have discussed, this frontal lobe region of the human brain helps control our impulses and restrains our behavior. AIc0h01 immobilizes that part of our brain first. As a result, we "loosen up, becoming less controlled and more extroverted. But anatomically targeted brain sedation it still is. Give alcohol a little more time, and it begins to sedate other parts 0f the brain, dragging them down into a stupefied state, just like the prefrontal cortex. You begin to feel sluggish as the inebriated torpor sets ⅲ . This is your brain slipping into sedation. Your desire and ability to remain conscious are decreasing, and you can let go Of consciousness more easily. I am very deliberately avoiding the term "sleep," however, because sedation is not sleep. Alcohol sedates you out Of wakefulness, but it does not induce natural sleep. The electrical brainwave state you enter via alC0h01 is not that Of natural sleep; rather, it is akin to a light form Of anesthesia. Yet this is not the worst ofit when considering the effects ofthe eve- ning nightcap on your slumber. More than its artificial sedating influ- ence, alcohol dismantles an individual's sleep ⅲ an additional vo ways. First, alcohol fragments sleep, littering the night with brief awaken- ings. Alcohol-infused sleep is therefore not continuous and, as a result, not restorative. Unfortunately, most Of these nighttime awakenings go unnoticed by the sleeper since they don't remember them. lndividuals therefore fail to link alcohol consumption the night before with feel-

WHY WE SLEEP ー 9 7 ity, then the particular dream should have little movement but be filled with visual objects and scenes and contain strong emotions— and vice versa.We have conducted just such an experiment, and the findings were so: we could predict with confidence theform of some- one's dream—would it be visual, would it be motoric, would it be awash with emotion, would it be completely irrational and bizarre?— before the dreamers themselves reported their dream experience to the research assistant. AS revolutionary as it was tO predict the generalform Of someones dream (emotional, visual, motoric, etc. ), it left a more fundamental question unanswered: Can we predict the CO 〃〃ー Of someones dream—that is, can we predict Ⅳん砒 an individual is dreaming about (). g ・ , a car, a woman, food), rather than just the 〃砒リ re 0f the dream (e ・ g ・ , is it visual)? ln 2013 , a research team in Japan, led by Dr. Yukiyasu Kamitani at the Advanced Telecommunications Research lnstitute lnternational ⅲ Kyot0, found an ingenious way to address the question. They essentially cracked the code of an individual's dream for the very first time and, in doing so, led us t0 an ethically uncomfortable place. lndividuals in the experiment consented tO the study—an impor- tant fact, as we shall see. The results remaln prelimnary, since they were obtained ⅲ just three individuals. But they were highly signifi- cant. AISO, the researchers focused on the short dreams we all fre- quently have just at the moment when we are falling asleep, rather than the dreams ofREM sleep, though the method will soon be applied to REM sleep. The scientists placed each participant intO an MRI scanner numer- ous times over the course ofseveral days. Every time the participant fell asleep, the researchers would wait for a short while as they recorded the brain activity, and then wake the person up and obtain a dream report. Then they would let the person fall back t0 sleep, and repeat the procedure. The researchers continued t0 d0 this until they had gath- ered hundreds of dream reports and corresponding snapshots of brain activity 仕 om their participants. An example ofone ofthe dream reports was:"l saw a big bronze statue … on a small hill, and below the hill there 、 houses, streets, and trees.

3 2 6 MAITHEW WALKER perature across the night that is in harmony with each body's expec- tations, rather than the constant nighttime temperature set ⅲ most homes and apartments. Over time, we could intelligently curate a tai- lored thermal sleep envlronrnent that is personalized tO the circadian rhythms of each individual occupant of each bedroom, departing 仕 om the unhelpful non-varying thermal backdrop that plagues the sleep of most people using standard home thermostats. BOth these changes reqmre no effort 仕 om an individual, and should hasten the speed 0f sleep onset, increase t0tal sleep time, and even deepen NREM-sleep quality for all household members ()s discussed in chapter 13 ). The second passive solution concerns electric light. Many of us suf- fer 仕 om overexpo sure to nighttime light, p articularly blue-dominant LED light 仕 om our digital devices. This evening digital light suppresses melatonin and delays our sleep timing. What if we can turn that prob- lem into a solution? Soon, we should be able to engneer LED bulbs with filters that can vary the wavelength oflight that they emit, rangmg 仕 om warm yellow colors less harmful to melatonin, t0 strong blue light that powerfully suppresses it. Paired with sleep trackers that can accurately characterize our personal biological rhythms, we can install these new bulbs through- out a home, all connected t0 the home network 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 ()r set of individuals') natural sleep-wake pattern. We could do this dynamically and seam- lessly as individuals move 仕 om one room to the next ⅲ real time. Here again we can intelligently split the difference on the fly based on the biophysiological mix of whoever is in the room. ln doing so, the users own brains and bodies, measured and translated through the wearables to the networked home, would synergistically regulate light and thus melatonin release that promotes, rather than impedes, optimal regula- tion ofsleep for one and . lt is a vision ofpersonalized sleep medicine. C01 れ e the morning, we can reverse thiS trick. can now saturate our indoor environments with powerful blue light that shuts offany lin- gering melatonin. This ⅷⅡ help us wake up faster, more alert, and with a brighter n100d , morning after morning.

2 8 8 MATTHEW WALKER the sources are many.. ln an attempt to find answers, Kripke and other independent research groups have now evaluated data 仕 om stud- ies involving almost all of the common sleeping pills, including zolpi- dem (Ambien), temazepam ()e storil), e szopiclone (Lune sta), z aleplon (Sonata), and other sedating drugs, such as triazolam (Halcion) and flurazepam (Dalmane). One frequent cause of mortality appears to be higher-than-nor- mal rates Of infection. AISO discussed in earlier chapters, natural sleep is one Of the most powerful boosters Of the immune system, helping ward 0ff infection. Why, then, d0 individuals who are tak- ing sleeping pills that purportedly "improve" sleep suffer んん rates Of various infections, when the opposite is predicted? lt is possible that medication-induced sleep does not provide the same restorative immune benefits as natural sleep. This would be most troubling for the elderly. Older adults are far more likely to suffer from infections. Alongside newborns, they are the most immunologically vulnerable individuals in our society. Older adults are also the heaviest users of sleeping pills, representing more than 50 percent 0f the individuals prescribed such drugs. Based on these coincidental facts, it may be time for medicine tO reappraise the prescription frequency of sleep- ing pills in the elderly. Another cause of death linked t0 sleeping pill use is an increased risk for fatal car accidents. This is most likely caused by the non- restorative sleep such drugs induce and/or the groggy hangover that some suffer, both ofwhich may leave individuals drowsy while driving the next day. Higher risk for falls at night was a further mortality fac- tor, particularly in the elderly. Additional adverse associations in users 0f prescription sleeping pills included higher rates of heart disease and stroke. Then broke the story of cancer. EarIier studies had hinted at a rela- tionship between the sleep medications and mortality risk 仕 om cancer, but were not as well controlled in terms ofcomparisons. Kripke's study did a far betterjob ⅲ this regard, and included the newer, more relevant sleeping medication Ambien. lndividuals taking sleeping pills were 30 t0 40 percent more likely to develop cancer within the two-and-a-half- year period 0f the study than those wh0 were not. The older sleeping

WHY WE SLEEP INDIVIDUAL TRANSFORMATION 3 2 5 lncreasing sleep for an individual can be achieved through both pas- sive methods, which reqmre no effort 仕 om the individual and are thus preferable, and active methods, which d0. Here are several possibilities that may not be so far-fetched, all of which build on proven scientific methods for enhancing sleep quantity and quality. The intrusion oftechnology intO our homes and bedrooms is claimed by many 0f my research colleagues t0 be robbing us 0f precious sleep, and I agree. Evidence discussed in this b00 に such as the harmful effects ofLED-emitting devices at night, proves this to be true. Scientists have therefore lobbied t0 keep sleep analog, as it were, in this increasingly digital world, leaving technology out ofthe discussion. Here, however, I actually disagree. Yes, the future of sleep is about a return tO the past ⅲ the sense that we must reunite with regular, plenti- ful sleep, as we once knew a century ago. But tO battle against rather than unite with technology is the wrong approach ⅲ my mind. For one thing, it's a losing battle: we will never put that technological genie back intO its bottle, nor dO we need tO. lnstead, we can use this powerful tOOl tO our advantage. Within three tO five years, I am (llllte certain there ⅶⅡ be commercially available, affordable devices that track an individ- ual's sleep and circadian rhythm with high accuracy. When that hap- pens, we can marry these individual sleep trackers with the revolution of in-home networked devices like thermostats and lighting. Some are already trying to do this as I write. Two exciting possibilities unfold. First, such devices could compare the sleep of each family member in each separate bedroom with the temperature sensed ⅲ each room by the thermostat. Using common machine-learning algorithms applied over time, we should be able t0 intelligently teach the home thermostat what the thermal sweet spot is for each occupant ⅲ each bedroom, based on the biophysiology cal- culated by their sleep-tracking device (perhaps splitting the difference when there are two or more individuals per room ). Granted there are many different factors that make for a good or bad night 0f sleep, but temperature is very much one ofthem. Better still, we could program a natural circadian lull and rise in tem-

W HY W E S L E E P deepest stages 0fNREM sleep and, at that point, switched on the brain stimulator, pulsing in rhythmic time with the slow waves. The electrical pulsations were so small that participants did not feel them, nor did they wake up. * But they had a measurable impact on sleep. B0th the size of the slow brainwaves and the number of sleep spindles riding on top 0f the deep brainwaves were increased by the stimulation, relative tO a control group Of subjects whO did not receive stimulation during sleep. Before being put t0 bed, all the participants had learned a list ofnew facts. They were tested the next morning after sleep. By boosting the electrical quality of deep-sleep brainwave activ- ity, the researchers almost doubled the number offacts that individuals were able to recall the following day, relative to those participants who received no stimulation. Applymg stimulation during REM sleep, or during wakefulness across the day, did not offer similar memory advan- tages. Only stimulation during NREM sleep, ⅲ synchronous time with the brain's own slowmantra rhythm, leveraged a memoryimprovement. Other methods for amplifying the brainwaves ofsleep are fast being developed. One technology involves quiet auditory tones being played over speakers next tO the sleeper. Like a metronome ⅲ rhythmic stride with the individual slow waves, the tick-tock tones are precisely syn- chronized with the individual's sleeping brainwaves to help entrain their rhythm and produce even deeper sleep. Relative to a control group that slept but had no synchronous auditory chimes at mght, the auditory stimulation increased the power Of the slow brainwaves and returned an impressive 40 percent memory enhancement the next morning. Before you drop this book and start installing speakers above your bed, or go shopping for an electrical brain stimulator, let me dissuade you. For both methods, the wisdom 0 ド do not try this at home" applies. Some individuals have made their own brain-stimulating devices, or bought such devices online, which are not covered by safety regula- tions. Skin burns and temporary losses ofvision have been reported by *This technique, called transcranial direct current brain stimulation (tDCS), should not be confused with electroconvulsive shock ther 叩 y, in which the size of electrical volt- age inserted intO the brain is many hundreds or thousands Of times stronger (the conse- quences 0f which were so arrestingly illustrated ⅲ Jack Nicholson's performance in the movie 0 〃 e 月 e ル Over the C ″ c 凾ル e 立 ).

WHY WE SLEEP 3 3 9 I know that may sound unwelcome t0 some ofyou. But it would not if you had lost a loved one tO a fatigue-related accident. FortunateIy, the rise Of semiautonomous-driving features ⅲ cars can help us avoid thiS issue. Cars can use these very same signatures offatigue tO heighten their watch and, when needed, take greater self-control ofthe vehicle 仕 om the driver. At the very highest levels, transforming entire societies ⅷⅡ be nei- ther trivial nor easy. Yetwe can borrowproven methods 仕 om other areas ofhealth to shift society's sleep for the better. I offerjust one example. ln the United States, many health insurance compames provide a financial credit t0 their members forjoimng a 部 , m. Considering the health bene- fits ofincreased sleep amount, why don't we institute a similar incentive for racking up more consistent and plentiful slumber? Health insurance companies could approve valid commercial sleep-tracking devices that individuals commonly own. You, the individual, could then upload your sleep credit score t0 your health-care provider profile. Based on a tiered, pro-rata system, with reasonable threshold expectations for different age groups, you would be awarded a lower insurance rate with increas- ing sleep credit on a month-to-month basis. Like exercise, this ⅲ turn ⅷⅡ help improve societal health en masse and lower the cost ofhealth- care utilization, allowing people t0 have longer and healthier lives. Even with lower insurance paid by the individual, health insurance companies would still gain, as it would significantly decrease the cost burden oftheir insured individuals, allowing for greater profit margms. Everyone wins. Ofcourse,just like a gym membership, some people will start off adhering to the regime but then stop, and some may look for ways tO bend or play the system regarding accurate sleep assessment. However, even ifonly 50 to 60 percent ofindividuals truly increase their sleep amount, it could save tens or hundreds 0f millions 0f dollars in terms Of health costs—not tO mention hundreds ofthousands Of lives. This tour ofideas offers, I hope, some message ofoptimism rather than the tabloid-like doom with which we are so often assaulted in the media regarding things health. More than hope, however, I wish for it t0 spark better sleep solutions 0f your own; ideas that some 0f you may translate intO a non- or for-profit commercial venture, perhaps.

4 8 MATT ・ HEW WALKER fact that different parts of your waking brain are processing different pieces Of information at different moments in time and ⅲ different ways.When summed together, they produce what appears to be a dis- combobulated pattern 0f activity recorded by the electrodes placed on your head. As an an 引 0 consider a large 応 otb stadium filled with thou- sands offans. Dangling over the middle ofthe stadium is a microphone. The individual people in the stadium represent individual brain cells, seated in different parts ofthe stadium, as they are clustered in different reglons 0f the brain. The microphone is the electrode, sitting on top of the head—a recording device. Before the game starts, all ofthe individuals in the stadium are speak- ing about different things at different times. They are not having the same conversation in sync. lnstead, they are desynchronized in their individual discussions. As a result, the summed chatter that we pick up 仕 om the overhead microphone is chaotic, lacking a clear, unified voice. When an electrode is placed on a subject's head, as done in my labo- ratory, it is measuring the summed activity Of all the neurons below the surface ofthe scalp as they process different streams ofinformation (sounds, sights, smells, feelings, emotions) at different moments in time and ⅲ different underlying locations. Processing that much informa- tion 0f such varied kinds means that your brainwaves are very fast, fre- netic, and chaotic. Once settled into bed at my sleep laboratory, with lights out and per- haps a few tosses and turns here and there, you will successfully cast off 仕 om the shores of wakefulness into sleep. First, you will wade out into the shallows of light NREM sleep: stages 1 and 2. Thereafter, you will enter the deeper waters of stages 3 and 4 ofNREM sleep, which are grouped together under the blanket term "slow-wave sleep. " Returning to the brainwave patterns of figure 9 , and focusing on the middle line, you can understand why. ln deep, slow-wave sleep, the up-and-down tempo ofyour brainwave activity dramatically decelerates, perhaps just tWO tO four waves per second: ten times slower than the fervent speed ofbrain activity you were expressing while awake. As remarkable, the slow waves of NREM are 記 so far more synchro- nous and reliable than those of your waking brain activity. So reliable,

WHY WE SLEEP ー 4 5 Of sleep deprivation, as can caffeine up tO a certain dose. But in the subsequent studies that Dinges and many other researchers (myself included) have performed, neither naps nor caffeine can salvage more complex functions of the brain, including learning, memory, emotional stability, complex reasoning, or decision-making. One day we may discover such a counteractive method. Currently, however, there is no drug that has the proven ability to replace those benefits that a んⅡ night of sleep infuses into the brain and body. David Dinges has extended an open invitation tO anyone suggesting that they can survive on short sleep t0 come t0 his lab for a ten-day stay. He ⅷⅡ place that individual on their proclaimed regiment of short sleep and measure their cognitive function. Dinges is rightly confident he'll show, categorically, a degradation ofbrain and body function. To date, no vo ト unteers have matched up tO their claim. Ⅵ厄 have, however, discovered a very rare collection of individuals whO appear tO be able tO survive on six hours Of sleep, and shOW min- imal impairment—a sleepless elite, as it were. Give them hours and hours 0f sleep opportunity ⅲ the laboratory, with no alarms or wake- up calls, and still they naturally sleep this short amount and no more. Part of the explanation appears to lie in their genetics, specifically a sub-variant 0f a gene called BHLHE41. * Scientists are now trying to understand what this gene does, and how it confers resilience tO such little sleep. Having learned this, I imagine that some readers now believe that they are one of these individuals. That is very, very unlikely. The gene is remarkably rare, with but a soupqon of individuals in the world esti- mated t0 carry this anomaly. TO impress this fact further, I quote one 0f my research colleagues, Dr. Thomas R0th at the Henry Ford Hospital in Detroit, who once said, "The number ofpeople who can survive on five hours ofsleep or less without any impalrment, expressed as a percent Of the population, and rounded tO a whOle number, is zero. There is but a fraction 0f 1 percent of the population who are truly resilient tO the effects Of chronic sleep restriction at all levels Of brain function. lt is far, far more likely that you ⅵⅡ be struck by lightning (the * 川 so known as DEC2.

WHY WE SLEEP By the end of that week, these ( formerly healthy) participants were 40 percent less effective at absorbing a standard dose Of glucose, com- pared t0 when they were fully rested. TO give you a sense Of what that means, if the researchers showed those b100d sugar readings to an unwitting family doctor, the GP would immediately classify that individual as being pre-diabetic. They would start a rapid intervention program tO prevent the development Of irre- versible り甲 e 2 diabetes. Numerous scientific laboratories around the world have replicated this alarming effect of short sleep, some with even less aggressive reductions in Sleep amount. How does a lack of sleep hijack the body's effective control of blood sugar? Was it ablockade ofinsulin release, removing the essential instruc- tion for cells to absorb glucose? Or had the cells themselves become unresponsive tO an otherwise norr れ記 and present message ofinsulin? As we have discovered, both are true, though the most compelling evidence indicates the latter. By taking small tissue samples, or biop- sies, 仕 om participants at the end of the above experiments, we can examine how the cells ofthe b0dy are operating. After participants had been restricted to four to five hours ofsleep for a week, the cells ofthese tired individuals had become far less receptive to insulin. ln this sleep- deprived state, the cells were stubbornly resisting the message 仕 om insulin and refusing t0 open up their surface channels. The cells were repelling rather than absorbing the dangerously high levels of glucose. The roadside drains were effectively closed shut, leading to a rising tide 0fb100d sugar and a pre-diabetic state of hyperglycema. While many ⅲ the general public understand that diabetes is seri- ous, they may not appreciate the true burden. Beyond the average treat- ment cost ofmore than $ 85 , 000 per patient (which contributes to higher medical insurance premiums), diabetes lops ten years offan individual's life expectancy. Chronic sleep deprivation is now recognized as one of the major contributors tO the escalation Of 与甲 e 2 diabetes throughout first-world countries. lt's a preventable contribution. WEIGHT GAIN AND OBESITY When your sleep becomes short, you will gain weight. MultipIe forces conspire tO expand your waistline. The first concerns two hormones