Why We Sleep Quotes

“So long as they are reliably repeating, the brain can also use other external cues, such as food, exercise, temperature fluctuations, and even regularly timed social interaction. All of these events have the ability to reset the biological clock, allowing it to strike a precise twenty-four-hour note.”
― Matthew Walker, Why We Sleep: Unlocking the Power of Sleep and Dreams

“The first factor is a signal beamed out from your internal twenty-four-hour clock located deep within your brain. The clock creates a cycling, day-night rhythm that makes you feel tired or alert at regular times of night and day, respectively. The second factor is a chemical substance that builds up in your brain and creates a “sleep pressure.” The longer you’ve been awake, the more that chemical sleep pressure accumulates, and consequentially, the sleepier you feel. It is the balance between these two factors that dictates how alert and attentive you are during the day, when you will feel tired and ready for bed at night, and, in part, how well you will sleep.”
― Matthew Walker, Why We Sleep: Unlocking the Power of Sleep and Dreams

“We are even beginning to understand the most impervious and controversial of all conscious experiences: the dream. Dreaming provides a unique suite of benefits to all species fortunate enough to experience it, humans included. Among these gifts are a consoling neurochemical bath that mollifies painful memories and a virtual reality space in which the brain melds past and present knowledge, inspiring creativity.”
― Matthew Walker, Why We Sleep: Unlocking the Power of Sleep and Dreams

“This book will reveal a very different truth: sleep is infinitely more complex, profoundly more interesting, and strikingly health-relevant. We sleep for a rich litany of functions, plural—an abundant constellation of nighttime benefits that service both our brains and our bodies. 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). That we receive such a bounty of health benefits each night should not be surprising.”
― Matthew Walker, Why We Sleep: Unlocking the Power of Sleep and Dreams

“Drowsy driving is the cause of hundreds of thousands of traffic accidents and fatalities each year. And here, it is not only the life of the sleep-deprived individuals that is at risk, but the lives of those around them. Tragically, one person dies in a traffic accident every hour in the United States due to a fatigue-related error.”
― Matthew Walker, Why We Sleep: Unlocking the Power of Sleep and Dreams

“Insufficient sleep appears to be a key lifestyle factor linked to your risk of developing Alzheimer’s disease.”
― Matthew Walker, Why We Sleep: Unlocking the Power of Sleep and Dreams

“A testable prediction emerged: if I could lower the levels of noradrenaline in the brains of PTSD patients during sleep, thereby reinstating the right chemical conditions for sleep to do its trauma therapy work, then I should be able to restore healthier quality REM sleep. With that restored REM-sleep quality should come an improvement in the clinical symptoms of PTSD, and further, a decrease in the frequency of painful repetitive nightmares. It was a scientific theory in search of clinical evidence. Then came the wonderful stroke of serendipity.”
― Matthew Walker, Why We Sleep: Unlocking the Power of Sleep and Dreams

“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. To sleep, perchance to heal.”
― Matthew Walker, Why We Sleep: Unlocking the Power of Sleep and Dreams

“I had been developing a theory based on the combined patterns of brain activity and brain neurochemistry of REM sleep, and from this theory came a specific prediction: REM-sleep dreaming offers a form of overnight therapy. That is, REM-sleep dreaming takes the painful sting out of difficult, even traumatic, emotional episodes you have experienced during the day, offering emotional resolution when you awake the next morning.”
― Matthew Walker, Why We Sleep: Unlocking the Power of Sleep and Dreams

“Sleep disruption may therefore increase the risk of cancer development and, if cancer is established, favor its rapid and more rampant growth. The scientific evidence linking disrupted sleep-wake rhythms and cancer is now so damning that the World Health Organization has officially classified nighttime shift work as a “probable carcinogen.”
― Matthew Walker, Why We Sleep: Unlocking the Power of Sleep and Dreams

“In the Northern Hemisphere, the switch to daylight savings time in March results in most people losing an hour of sleep opportunity. Should you tabulate millions of daily hospital records, as researchers have done, you discover that this seemingly trivial sleep reduction comes with a frightening spike in heart attacks the following day. Impressively, it works both ways.”
― Matthew Walker, Why We Sleep: Unlocking the Power of Sleep and Dreams

“When communicating science to the general public in lectures or writing, I’m always wary of bombarding an audience with never-ending mortality and morbidity statistics, lest they themselves lose the will to live in front of me. It is hard not to do so with such compelling masses of studies in the field of sleep deprivation.”
― Matthew Walker, Why We Sleep: Unlocking the Power of Sleep and Dreams

“am in no way contesting the disorder of ADHD, and not every child with ADHD has poor sleep. But we know that there are children who are sleep-deprived or suffering from an undiagnosed sleep disorder that masquerades as ADHD. They are being dosed for years of their critical development with amphetamine-based drugs.”
― Matthew Walker, Why We Sleep: Unlocking the Power of Sleep and Dreams

“If you make a composite of these symptoms (unable to maintain focus and attention, deficient learning, behaviorally difficult, with mental health instability), and then strip away the label of ADHD, these symptoms are strongly overlapping with those caused by a lack of sleep. Take an under-slept child to a doctor and describe these symptoms without mentioning the lack of sleep, which is not uncommon, and what would you imagine the doctor is diagnosing the child with, and medicating them for? Not deficient sleep, but ADHD.”
― Matthew Walker, Why We Sleep: Unlocking the Power of Sleep and Dreams

“Children from lower socioeconomic backgrounds are less likely to be taken to school in a car, in part because their parents often have jobs in the service industry demanding work start times at or before six a.m. Such children therefore rely on school buses for transit, and must wake up earlier than those taken to school by their parents. As a result, those already disadvantaged children become even more so because they routinely obtain less sleep than children from more affluent families.”
― Matthew Walker, Why We Sleep: Unlocking the Power of Sleep and Dreams

“Only then did scientists realize the rather profound conclusions of the experiment: REM sleep is what stands between rationality and insanity. Describe these symptoms to a psychiatrist without informing them of the REM-sleep deprivation context, and the clinician will give clear diagnoses of depression, anxiety disorders, and schizophrenia. But these were all healthy young individuals just days before. They were not depressed, weren’t suffering from anxiety disorders or schizophrenia, nor did they have any history of such conditions, self or familial. Read of any attempts to break sleep-deprivation world records throughout early history, and you will discover this same universal signature of emotional instability and psychosis of one sort or another. It is the lack of REM sleep—that critical stage occurring in the final hours of sleep that we strip from our children and teenagers by way of early school start times—that creates the difference between a stable and unstable mental state.”
― Matthew Walker, Why We Sleep: Unlocking the Power of Sleep and Dreams

“Forced by the hand of early school start times, this state of chronic sleep deprivation is especially concerning considering that adolescence is the most susceptible phase of life for developing chronic mental illnesses, such as depression, anxiety, schizophrenia, and suicidality. Unnecessarily bankrupting the sleep of a teenager could make all the difference in the precarious tipping point between psychological wellness and lifelong psychiatric illness.”
― Matthew Walker, Why We Sleep: Unlocking the Power of Sleep and Dreams

“There was another equally intriguing result: in the days after a supervisor had slept poorly, the employees themselves, even if well rested, became less engaged in their jobs throughout that day as a consequence. It was a chain-reaction effect, one in which the lack of sleep in that one superordinate person in a business structure was transmitted on like a virus, infecting even well-rested employees with work disengagement and reduced productivity.”
― Matthew Walker, Why We Sleep: Unlocking the Power of Sleep and Dreams

“Studies in the workplace have found that 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. Seminal work by Dr. Christopher Barns, a researcher in the Foster School of Business at Washington University, has found that the less an individual sleeps, the more likely they are to create fake receipts and reimbursement claims, and the more willing to lie to get free raffle tickets. Barns also discovered that under-slept employees are more likely to blame other people in the workplace for their own mistakes, and even try to take credit for other people’s successful work: hardly a recipe for team building and a harmonious business environment.”
― Matthew Walker, Why We Sleep: Unlocking the Power of Sleep and Dreams

“A standardized way to appreciate the impact is by looking at gross domestic product (GDP)—a general measure of a country’s profit output, or economic health. Viewed this way, things look even more bleak, described in figure 16B. Insufficient sleep robs most nations of more than 2 percent of their GDP—amounting to the entire cost of each country’s military. It’s almost as much as each country invests in education. Just think, if we eliminated the national sleep debt, we could almost double the GDP percentage that is devoted to the education of our children. One more way that abundant sleep makes financial sense, and should itself be incentivized at the national level.”
― Matthew Walker, Why We Sleep: Unlocking the Power of Sleep and Dreams

“Less surprising, perhaps, is the inverse relationship between sleep and next-day exercise (rather than the influence of exercise on subsequent sleep at night). When sleep was poor the night prior, exercise intensity and duration were worse the following day. When sleep was sound, levels of physical exertion were powerfully maximal the next day. In other words, sleep may have more of an influence on exercise than exercise has on sleep.”
― Matthew Walker, Why We Sleep: Unlocking the Power of Sleep and Dreams

“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. Environmental light and temperature therefore synergistically, though independently, dictate nightly melatonin levels and sculpt the ideal timing of sleep.”
― Matthew Walker, Why We Sleep: Unlocking the Power of Sleep and Dreams

“The overnight work of REM sleep, which normally assimilates complex memory knowledge, had been interfered with by the alcohol. More surprising, perhaps, was the realization that the brain is not done processing that knowledge after the first night of sleep. 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.”
― Matthew Walker, Why We Sleep: Unlocking the Power of Sleep and Dreams

“The real surprise came in the results of the third group of participants. Despite getting two full nights of natural sleep after initial learning, having their sleep doused with alcohol on the third night still resulted in almost the same degree of amnesia—40 percent of the knowledge they had worked so hard to establish on day 1 was forgotten.”
― Matthew Walker, Why We Sleep: Unlocking the Power of Sleep and Dreams

“You don’t have to be using alcohol to levels of abuse, however, to suffer its deleterious REM-sleep-disrupting consequences, as one study can attest. Recall that one function of REM sleep is to aid in memory integration and association: the type of information processing required for developing grammatical rules in new language learning, or in synthesizing large sets of related facts into an interconnected whole.”
― Matthew Walker, Why We Sleep: Unlocking the Power of Sleep and Dreams

“On day 7, participants in the control condition remembered everything they had originally learned, even showing an enhancement of abstraction and retention of knowledge relative to initial levels of learning, just as we’d expect from good sleep. In contrast, 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 percent of all that original knowledge. This fits well with evidence we discussed earlier: that of the brain’s non-negotiable requirement for sleep the first night after learning for the purposes of memory processing.”
― Matthew Walker, Why We Sleep: Unlocking the Power of Sleep and Dreams

“Second, alcohol will often suppress REM sleep, especially during the first half or two-thirds of the night. When the body metabolizes alcohol it produces by-product chemicals called aldehydes and ketones. The aldehydes in particular will block the brain’s ability to generate REM sleep. It’s rather like the cerebral version of cardiac arrest, preventing the pulsating beat of brainwaves that otherwise power dream sleep. People consuming even moderate amounts of alcohol in the afternoon and/or evening can inadvertently deprive themselves of dream sleep.”
― Matthew Walker, Why We Sleep: Unlocking the Power of Sleep and Dreams

“While the reasons remain unclear, insomnia is almost twice as common in women than in men, and it is unlikely that a simple unwillingness of men to admit sleep problems explains this very sizable difference between the two sexes. Race and ethnicity also make a significant difference, with African Americans and Hispanic Americans suffering higher rates of insomnia than Caucasian Americans—findings that have important implications for well-recognized health disparities in these communities, such as diabetes, obesity, and cardiovascular disease, which have known links to a lack of sleep.”
― Matthew Walker, Why We Sleep: Unlocking the Power of Sleep and Dreams

“One example is language learning, and the extraction of new grammatical rules. Children exemplify this. They will start using the laws of grammar (e.g., conjunctions, tenses, pronouns, etc.) long before they understand what these things are. It is during sleep that their brains implicitly extract these rules, based on waking experience, despite the child lacking explicit awareness of the rules.”
― Matthew Walker, Why We Sleep: Unlocking the Power of Sleep and Dreams

“After time spent awake across the day, despite the chance to consciously deliberate on the problem as much as they desired, a rather paltry 20 percent of participants were able to extract the embedded shortcut. Things were very different for those participants who had obtained a full night of sleep—one dressed with late-morning, REM-rich slumber. Almost 60 percent returned and had the “ah-ha!” moment of spotting the hidden cheat—which is a threefold difference in creative solution insight afforded by sleep! Little wonder, then, that you have never been told to “stay awake on a problem.” Instead, you are instructed to “sleep on it.” Interestingly, this phrase, or something close to it, exists in most languages (from the French dormir sur un problem, to the Swahili kulala juu ya tatizo), indicating that the problem-solving benefit of dream sleep is universal, common across the globe.”
― Matthew Walker, Why We Sleep: Unlocking the Power of Sleep and Dreams