“If you had asked me that morning, ‘Arianna, how are you?’ I would’ve said, ‘Fine.’ It was really the fact that being depleted, running on empty, had become the new normal for me.”
The day Arianna Huffington fainted from exhaustion—an incident that left her with a broken cheekbone and five stitches near her right eye—marked the beginning of a profound reevaluation of the role of sleep in her life. Widely regarded as one of the most influential women in the world and then serving as president and editor-in-chief of the Huffington Post Media Group, Huffington insists her real success only began when she finally allowed herself to sleep enough. “The way to a more productive, more inspired, more joyful life is getting enough sleep,” she says. While acknowledging that success can come at the cost of rest, Huffington advocates for a more sustainable, expansive kind of success—one that does not sacrifice health and relationships but is instead built on recognising the essential role of sleep in human wellbeing.
According to the U.S. National Sleep Foundation, adults between the ages of 18 and 65 should get between seven and nine hours of sleep per night. In 1942, a Gallup poll revealed that only 11 percent of Americans slept fewer than six hours per night. Today, that figure has climbed to 41 percent.
Sleep is so fundamental that even animals require it—fish, insects, and reptiles all have distinct ways of resting. Yet despite its universality, scientists still cannot fully explain why we spend more than a third of our lives asleep.
After fifty years of research into the causes of sleep, William Dement, founding chair of Stanford Sleep Medicine Center, offered a wry conclusion: “As far as I know, the only reason we need to sleep that is really, really solid is because we get sleepy.”
One of the many theories about sleep—the restoration theory—argues that we rest because the body needs repair. While we sleep, the body restores, replaces, and rebuilds. This explanation was proposed more than 2,000 years ago and has been given new weight by modern findings showing that “indeed, a whole host of genes are “‘turned on’ only during sleep—genes associated with restoration and metabolic pathways,” neuroscientist Russell Foster says.
Another compelling theory is memory consolidation, which connects the entire learning process to the quality and quantity of our sleep. The new evidence supporting this theory is striking: although we need to absorb vast amounts of information throughout our lives, we often neglect to give the brain the very gift it needs to retain and successfully integrate that information—a good night’s sleep.
Tell me how much you sleep, and I’ll tell you how strong your memory is
“Sleep is the price the brain must pay for learning and memory,” says Giulio Tononi, a researcher at the University of Wisconsin. During waking hours, our brains take in a flood of data—numbers, ideas, thoughts, feelings, and sensory impressions. Not all of it is worth keeping, so the brain engages in a kind of sorting process, much of which happens during sleep.
Tononi and his colleague, Dr. Chiara Cirelli, developed the synaptic homeostasis hypothesis to explain sleep’s role in storing new information. While we sleep, the brain essentially resets, the two researchers argue. Their studies show that our synapses shrink by about 20 percent during sleep—a crucial step for learning, because the strong neural connections formed while awake are less receptive to new information.
Without sleep, the brain would be overwhelmed by the massive volume of data encoded by synapses. Sleep allows it instead to integrate fresh information into the network of existing memories and to carry out a kind of editing process, discarding what is nonessential.
One study on infants underscored the role of sleep as the foundation of memory. Conducted by researchers at the University of Sheffield in the UK and Ruhr University Bochum in Germany, it found that babies who failed to get enough sleep shortly after learning new tasks were unable to recall them later. Half of the infants slept for four hours after learning new games, and the next day they could reproduce 50 percent of the actions. By contrast, those who either skipped sleep or napped for no more than 30 minutes retained far less.
It isn’t only infants who benefit from sleep—daytime naps also play a crucial role in children’s learning. Professor Jakke Tamminen of Royal Holloway, University of London, has studied how sleep supports language development. His laboratory research shows that during slow-wave sleep (SWS), a deep non-REM phase, the hippocampus—responsible for rapid learning—maintains constant communication with the neocortex, which consolidates those lessons. Slow-wave sleep may be one of the key factors that enable children to absorb information more easily, including foreign languages. “Children need to sleep during the day to remember everything that they have to learn,” says Dominique Petit, coordinator of the Canadian Sleep and Circadian Network.
Students, too, should resist the temptation to sacrifice a full night’s rest during exams, even if it seems like a shortcut to cramming more material at the last minute. On the contrary, “that’s the worst thing you can do,” Tamminen warns his students.
One of his research projects shows that all-nighters during exam periods do little to support the efficient assimilation of information. In the study, participants learned lists of new words, then stayed awake all night before being tested in several stages to measure how many words they had retained. Even after several nights of trying to recover lost sleep, there were still significant differences between this group and the control group, which had not been deprived of sleep, in their ability to recall the words they had memorised. The professor’s conclusion is clear: sleep is a central part of human learning. “Even though you’re not studying when you sleep, your brain is still studying. It’s almost like it’s working on your behalf.”
If we fully understood how intensely memory is strengthened during rest, we would learn to time and structure sleep according to the nature of the information we encounter in a given day. If we want to retain it, it is essential to sleep enough after being exposed to it; if we would rather forget, at least partially, what we have learned or experienced, delaying sleep becomes crucial. For example, soldiers returning from difficult missions should not go straight to bed. In fact, preventing post-traumatic stress disorder requires that soldiers exposed to violent experiences remain awake for at least six to eight hours, Gina Poe of the University of California says. Research conducted by Poe and her colleagues shows that sleeping immediately after traumatic events—before the brain has had time to process the information—actually increases the likelihood of those experiences being consolidated into long-term memories.
How sleepless nights cost us in physical and mental well-being
Research from the past few decades has provided ample reasons to rethink our attitude toward sleep—from seeing it as an intruder that steals years of our lives and can be cheated with a cup of coffee, to recognising it as the backbone of a healthy life.
“No aspect of our biology is left unscathed by sleep deprivation,” says Matthew Walker, professor of psychology and neuroscience at the University of California. For more than two decades, Walker has studied sleep—and he practices what he preaches, sleeping eight hours a night and keeping a strict schedule for bedtime and waking. “Once you know that after just one night of only four or five hours’ sleep, your natural killer cells—the ones that attack the cancer cells that appear in your body every day—drop by 70%, or that a lack of sleep is linked to cancer of the bowel, prostate and breast, or even just that the World Health Organization has classed any form of night-time shift work as a probable carcinogen, how could you do anything else?”
The evidence Walker presents in his book Why We Sleep makes a powerful impression, says Rachel Cooke in The Guardian.
More than 20 epidemiological studies show that there is no alternative to quality sleep—every hour counts in tipping the balance between longevity and health on the one hand, and premature death and disease on the other. One study found that mortality rates from ischemic heart disease, cancer, and stroke were lowest among people who slept seven to eight hours per night. By contrast, adults over 45 who sleep fewer than six hours a night are 200 percent more likely to suffer a heart attack or stroke in their lifetime compared to those who get seven to eight hours of rest.
Insufficient sleep also appears to be linked to a higher risk of Alzheimer’s disease. During deep sleep, the brain clears out a toxic protein called beta-amyloid. When sleep is inadequate, this protein continues to build up—particularly in the regions of the brain responsible for deep sleep—damaging them and raising the risk of dementia.
Sleep deprivation also takes a toll on the reproductive system. Men who sleep only five to six hours a night have testosterone levels comparable to men ten years older.
“There is some evidence that sleep deprivation could lead to pre-diabetic state,” says Mark Mahowald, MD, director of the Minnesota Regional Sleep Disorders Center. According to Mahowald, the body’s response to insufficient sleep resembles insulin resistance, a precursor to diabetes.
Too little sleep also makes the body more prone to weight gain. It lowers levels of leptin—the hormone that signals satiety to the brain—while increasing levels of ghrelin, the hormone that stimulates appetite. While Matthew Walker cautions that it is simplistic to attribute the obesity epidemic solely to lack of sleep, factoring it in alongside sedentary lifestyles and poor diets offers a clearer picture of the problem.
When you don’t sleep, you can be a danger to others as well
Sleep deprivation doesn’t only affect the individual—it is also behind many accidents that claim lives.
Researchers at The George Institute for Global Health in Sydney found, in a study of 19,000 young people aged 19 to 24, that those who slept no more than six hours a night faced a 21% higher risk of being involved in a car accident during the week, with the risk rising to 55% on weekends. The problem is not unique to Australia, the researchers emphasise, noting that between 5% and 30% of accidents in the U.S., the U.K., and Australia are caused by driver fatigue—and, more seriously, sleep deprivation leads to crashes that “are more likely to be fatal compared with other crash causes.”
In February 2009, a commuter plane traveling from Newark to Buffalo crashed, killing 49 people—everyone on board and one person on the ground. The National Transportation Safety Board concluded that the performance of the two pilots had been impaired by fatigue, as both had slept very little before the flight.
Reports of disasters caused by sleep deprivation are especially frustrating for Harvard researcher Charles Czeisler, given how much is already known about the risks of insufficient rest—knowledge that should compel people to change harmful habits. Czeisler points out that sleeping five hours a night for a week, or staying awake for 24 hours straight, has the same effect as a blood alcohol level of 0.1%. “We would never say, ‘This person is a great worker! He’s drunk all the time!’” he says, highlighting the double standard at the heart of modern business ethics.
About a decade ago, Charles Czeisler began publishing reports based on studies of 2,700 medical residents who routinely worked 30-hour shifts, twice a week. The public health risks of such extreme sleep deprivation are all too often borne by patients, he says. One in five residents admitted that fatigue had led them to make a decision that harmed a patient, while one in twenty acknowledged that their mistake had resulted in a patient’s death. Although his research has yet to trigger major changes in hospital management, Czeisler hopes that in time this practice will come to be regarded as a form of barbarism.
Where we lost sleep—and how to get it back
There are several main reasons behind today’s widespread sleep disruption, Matthew Walker says. Chief among them is electricity, which allowed us to turn night into day: “Light is a profound degrader of our sleep.” Modern work patterns have also shrunk the boundaries of sleep—we work longer hours, lose more time commuting, and that eats into family and leisure, leaving cutting back on sleep as the only “convenient” option. Anxiety, depression, loneliness, alcohol, and caffeine are other factors fueling the deficit, he says.
Finally, Walker points to the negative modern perception of long sleep, which has come to be associated with weakness and inefficiency. Skimping on rest is treated as a badge of busyness—and therefore of success.
For those thinking of solving sleep problems—often self-inflicted by disregarding regular rest schedules—with sleeping pills, Czeisler issues a warning: these drugs “are not a natural way to sleep.” Regular use carries risks, including psychological dependence, worsening insomnia, and damage to memory.
We are, after all, complex beings—which means a simplistic approach to sleep disorders can do more harm than good. “Sleep is not monolithic. It’s not a marathon; it’s more like a decathlon. It’s tempting to manipulate sleep with drugs or devices, but we don’t yet understand sleep enough to risk artificially manipulating the parts,” neurologist Jeffrey Ellenbogen says.
Unless sleep is being disrupted by medical conditions that require treatment, there are straightforward ways to achieve better rest—even if quality sleep has felt out of reach for some time. The key lies in respecting the body’s need for consistent sleep patterns. One practical method is gradually adjusting bedtime by going to bed a little earlier each night until reaching the desired hour. It takes time for the body to adapt, says Rafael Pelayo of the Sleep Medicine Center, because moving sleep earlier is harder than pushing it later. Ultimately, perseverance pays off—even for those accustomed to falling asleep in the early hours of the morning. The caveat: even a single very late night can undo much of the progress.
Exposure to the blue light emitted by electronic screens should end a few hours before bedtime, since one of its effects is to disrupt the body’s production of melatonin—the hormone that regulates each person’s internal clock.
Sometimes change doesn’t require Herculean effort—just small, steady steps that follow a clear path. And when the harm we inflict by pushing sleep to the bottom of our priorities, or the benefits we gain from quality rest, aren’t enough to motivate us, it may help to look beyond ourselves, to those closest to us—our children, partners, parents. Their well-being and happiness depend in no small part on our own.
Giving yourself the sleep your body needs is a bit like the safety instructions on a plane: in an emergency, you’re told to put on your own oxygen mask first, Arianna Huffington says. After a night of restorative rest, the morning feels brighter, harder to ignore—and we can be, much to our own benefit and to those around us, the very best version of ourselves.