When I met with His Holiness the Dalai Lama, he was eighty-three years old and had just published his 125th book. “How do you stay so mentally fit?” I asked him.
“Sleep,” he said without missing a beat. “Nine hours a night.”
“Every night?”
“Every night.”
Sleep is restorative. While you’re unconscious of what’s going on around you, possibly immersed in a world of dreams and weird thoughts, your entire body and brain chemistry change. Cellular repair and cleansing mechanisms kick into overtime. Wound healing and fighting off of bacterial and viral infections increase in intensity. It’s only recently that we’ve begun to appreciate the enormous amount of cognitive processing that occurs while we’re asleep. Consolidation of memories takes place, alongside problem solving, categorization, and emotional processing.
The neural and cellular basis of the need for sleep has been called the sleep drive. Neuroscientists still don’t understand where that drive comes from, but it can be conceptualized as a homeostatic pressure that builds up during the waking hours and dissipates during sleep. We do know that there are chemicals in the brain that lead us to feel sleepy—somnogenic agents such as melatonin and adenosine—and the gradual accumulation of them creates this homeostatic pressure.
Consistent with the kinds of individual differences we looked at in Chapter 1, people regard sleep differently. Some look forward to it and some see it rather neutrally, as a necessity such as brushing your teeth, and don’t give it much of an affective connotation one way or another. A third group sees it as something to be avoided at any cost, for as long as possible.
In the “looking forward to sleep” camp there are some who just like it because it is pleasant—it feels good. Then there are some, like songwriter Billy Joel, who find it a great source of inspiration and creativity. His album River of Dreams is a nod to the fact that many of his ideas for songs came to him during sleep. “I wake up every morning, I get out of bed and I’ve got a song idea in my head. Not necessarily a song idea, but either a melodic idea or a symphonic idea. I dream symphonies sometimes.” Paul McCartney wrote one of the Beatles’ greatest hits, “Yesterday,” in his sleep, and Keith Richards wrote the main riff to the Rolling Stones’ “(I Can’t Get No) Satisfaction” in his sleep, woke up and recorded the guitar part on tape, and then went back to sleep. Stephen Stills wrote one of his most loved songs, “Pretty Girl Why,” during a dream.
In the “put sleep off as long as possible” camp, Thomas Edison viewed sleep and nightfall as annoyances, as “nuisances to be vanquished.” Edison was a workaholic and his development of the incandescent light bulb allowed him to work more hours in the day. (Some say Edison “invented” the incandescent bulb—but a long list of at least twenty others preceded Edison’s work on it, which largely was to refine it.) Writer David Kamp notes that the refinement of the light bulb “was as much a profound upending of the natural order as it was a huge technological advance—the first step on the path to our current age of screen addiction, overlong workdays and sleep deficits.” And the first step in tricking nature’s pineal gland into thinking it was daytime when it was not; the first step in messing with our chronobiological clocks; and the first step in creating several generations of artificial-light-induced insomniacs.
Joni Mitchell is also in the sleep-avoidance camp, and for most of her adult life she would drink as many as ten cups of coffee a day and smoke three packs of cigarettes in order to put off sleep. She got some of her best work done in the middle of the night when there were no distractions, no phones ringing, and no human-made noises outside her home. (On the occasions when she and I worked together, it was often between midnight and four A.M.)
Although putting off sleep may work for an occasional few nights, it is a bad long-term strategy. In his new book, Why We Sleep, UC Berkeley neuroscientist Matthew Walker warns that we are in the midst of a “catastrophic sleep loss epidemic” that poses “the greatest public health challenge we face in the 21st century.” Many have claimed that climate change, obesity, and access to clean water are greater threats to public health, but even if sleep loss comes in at #4, it is a serious threat—and one that each of us as individuals can do something about directly.
You may have read somewhere that each individual has their own sleep requirement that can vary from only a few hours to ten or twelve a night. Although this is technically true, the proportion of people who can get along on fewer than five hours of sleep a night without showing major impairment is tiny—less than half of 1 percent. You may be one of those, but it is not at all likely that you are. The idea that older adults need less sleep is a myth. They tend to get less sleep, but they still need the eight hours that the rest of us need.
Today, about half of adults sleep less than seven hours a night. Why? Here’s Walker:
First, we electrified the night. Light is a profound degrader of our sleep. Second, there is the issue of work: not only the porous borders between when you start and finish, but longer commute times, too. No one wants to give up time with their family or entertainment, so they give up sleep instead. And anxiety plays a part. We’re a lonelier, more depressed society. Alcohol and caffeine are more widely available. All these are the enemies of sleep.
Walker also points to one of the parts of the developmental science triune as a culprit—culture:
We have stigmatized sleep with the label of laziness. We want to seem busy, and one way we express that is by proclaiming how little sleep we’re getting. It’s a badge of honor. When I give lectures, people will wait behind until there is no one around and then tell me quietly: “I seem to be one of those people who need eight or nine hours’ sleep.” It’s embarrassing to say it in public. . . . Humans are the only species that deliberately deprive themselves of sleep for no apparent reason.
Sleep deprivation can occur in two primary ways—it can be of either insufficient duration or insufficient quality. That is, you may sleep eight hours a night, but for various reasons you may not pass through the requisite stages of sleep, or you may not stay in each of them the optimal amount of time. You may think you’re asleep when you’re not. Or, if you have sleep apnea, you may be waking hundreds of times during the night without realizing it.
Healthy, productive sleep allows the body to engage in cellular repair mechanisms—normal cellular housekeeping and immune-system responses—and helps us to process difficult emotions and replenish our energy levels.
The Roman poet Ovid knew something about these functions of sleep more than two thousand years ago:
Sleep, thou repose of all things; thou gentlest of the deities; thou peace of the mind, from which care flies; who dost soothe the heart of men wearied with the toils of the day, and refittest them for labor.
One of the functions of sleep is to process the most emotionally intense experiences of the previous day, to separate the facts from our feelings so that we can reach a quasi-objective view of things. The other reason for doing so is so that the emotions themselves can be entered into and stored in memory. It is of value to be able to access a memory based not just on a particular time or a particular place (which we can all do), but also on a particular emotion. All the experiences you’ve had of being humiliated, for example, can be bound together through emotional memory, in order to help you extract patterns and (hopefully) modify your future behavior. Sleep-deprived people show a 60 percent greater activation in their amygdala during waking hours than those who are not sleep-deprived. Because the amygdala is part of the brain’s fear circuit and is known to trigger aggression, anger, and rage, this finding highlights the relation between sleep deprivation and emotional regulation. When your mom told you that you were being crabby because you didn’t get enough sleep, she was probably right.
The act of living and staying awake, going about our business, leads to a buildup of toxins in the blood and brain. Cerebrospinal fluid circulates throughout the brain and spinal cord, and it clears away toxins through a series of channels (like waterways) that expand during sleep. Almost none gets cleared away while you are awake. Why all this happens better during sleep than during wakefulness is not fully understood. Too little sleep, or—perhaps counterintuitively—too much sleep, impairs problem solving, attention to detail, memory, motivation, and reasoning.
A U-shaped distribution has been uncovered, showing that people who sleep less than seven hours a night or more than ten are at an increased risk for hypertension. Similarly, sleep duration of less than six hours or more than nine is associated with increased prevalence of diabetes and impaired glucose tolerance. Poor sleep duration or quality, as well as too much sleep, also increases stress and allostatic load—the cumulative effects of stress over time.
If I haven’t frightened you into taking sleep seriously yet, sleep deprivation is now strongly associated with Alzheimer’s. Alzheimer’s disease occurs when a certain kind of protein, amyloid, builds up in the brain, where it forms clumps that collect between neurons, which in turn disrupt cell function. During proper, restorative sleep, these amyloid deposits get cleaned out of the brain through the action of the cerebrospinal fluid. When you’re sleep-deprived—either from short duration or poor-quality sleep—these amyloid deposits don’t get cleaned out, and they tend to selectively attack regions in the brain responsible for sleep, which then makes it even more difficult to sleep and, consequently, more difficult to clear out the amyloids. A vicious, sleepless, memory-killing cycle. And it doesn’t happen only in chronic sleep deprivation—a study published the week I first drafted this paragraph showed evidence from PET scans that amyloid plaque deposits build up in the brain after only a single night without sleep. (Under the protocol, participants may have managed to sneak in short catnaps during the night, but nurses were vigilant, checking on them every hour throughout the night and waking them if necessary.) The areas most impacted by sleep deprivation were the hippocampus (memory) and the thalamus (control of sleep-wake cycles). It is becoming clear that a lack of sleep, particularly a chronic lack, can lead to Alzheimer’s disease. If you want to lengthen your health span, better to follow Ovid than Edison.
We sleep in roughly ninety-minute cycles, comprising stages that are neurochemically and electrophysiologically distinctive. You’ve probably heard of the two kinds of sleep, REM and non-REM. REM stands for rapid eye movement sleep, the time when we are typically dreaming. Non-REM sleep occurs first, in four stages, with increasingly deep sleep, during which the frequency of brain waves slows down.
While considering a mental hospital and its residents, Charles Dickens wondered, in his essay “Night Walks,” about the feeling that dreams are a form of insanity:
Are not the sane and the insane equal at night as the sane lie a dreaming? Are not all of us outside this hospital, who dream, more or less in the condition of those inside it, every night of our lives?
Dreams help us to work things out—to let thoughts that are too dangerous, insane, or distressing have a safe haven in our minds, while our bodies are temporarily paralyzed, preventing us from entering into dangerous real-world situations. (A small proportion of people don’t experience paralysis during their dreaming. Sometimes it is drug induced: The sleep medication Ambien has been associated with sleepwalking, sleep-eating, sleep-driving, and a number of disturbing accidents and crimes, including at least two murders.)
REM sleep helps us to maintain emotional balance. And a lot of what happens during REM sleep is simply random neural firing that has no particular meaning. Non-REM sleep is when our memories of the previous day are consolidated and linked with previous experiences. If you meet someone new at a party named Mary, your brain—without your instructing it to do so, and without your conscious awareness—will recall her face and gestures and link them to the things she said and to her name. It may link to other people you know who remind you of her, and other people you know named Mary. While we enjoy non-REM sleep, our brains toss and turn over the experiences of the previous day (or two, if you stayed up all night), making connections between those and similar, past experiences.
This is especially true for procedural or motor learning. If you learn to play a musical instrument, do a Rubik’s cube, or take up salsa dancing, your motor movements need to be encoded in memory. But learning wouldn’t happen if in each lesson you were starting from scratch—the lessons need to build on one another. In order to do that, the fine motor and muscle movements you make today need to be integrated at a neural level with what happened on previous days. For lifelong skills, many years’ and decades’ worth of neural traces become linked to the new ones. Sleep does this.
Walker describes what’s happening in the brain during non-REM sleep as a kind of “synchronized pattern of rhythmic chanting.” He writes:
Researchers were once fooled that this state was similar to a coma. But nothing could be further from the truth. Vast amounts of memory processing is going on. To produce these brainwaves, hundreds of thousands of cells all sing together, and then go silent, and on and on. Meanwhile, your body settles into this lovely low state of energy, the best blood-pressure medicine you could ever hope for.
Acetylcholine levels drop during non-REM sleep and then reach a peak during REM sleep, helping to prevent outside inputs from disturbing your dreaming. Acetylcholine is also an important chemical that mediates memory consolidation. If levels of it are reduced in the brain, or delayed, memory can be impaired for several days. Melatonin and acetylcholine levels trade off with norepinephrine levels during sleep—the former two reach a peak at bedtime, while norepinephrine, a neurotransmitter responsible for action and wakefulness, is decreased.
Passing through non-REM and then REM sleep adds up to a sleep cycle. A great deal gets done during such cycles, and it appears that we need five or six of them to reach full restoration. How do you know whether you’re getting enough sleep? Unless you’ve got certain medical conditions or are taking medications that cause fatigue, a simple rule of thumb is that if you can’t wake up in the morning without an alarm clock and you feel sleepy before lunch, either you are sleep-deprived or, as we saw in Chapter 8, your circadian clock is misaligned. To determine your personal amount of sleep needed, find a two-week period when you can afford to experiment, a period during which you’re not under any particular stress or deadlines and when you have free evenings—no late-night dinners. Try to avoid alcohol and caffeine, or, if you must have caffeine, try to limit yourself to two or three servings a day, and none within seven hours of bedtime. Sleep in a darkened room where sunlight won’t disturb you in the morning. Then just go to sleep when you’re tired and wake up when you feel like waking up, without an alarm. Keep a log of your sleep and wake times. If, like most of us, you’ve been sleep-deprived for some time, you’ll need to pay back your sleep debt. Near the end of the two weeks, however, your body should have settled into a rhythm and you should be able to wake up without the alarm, feeling refreshed.
We’ve seen that aging is typically associated with a reduced ability to adapt to environmental changes, impairments in perception and normal physiological functioning, and an increased susceptibility to disease through reductions in immune-system efficacy. The time course at which all these changes become noticeable varies from person to person, but it’s rare that someone over eighty hasn’t noticed these changes, and many people notice them after fifty-five.
It’s not surprising, then, that changes in sleep biology accompany aging as well. The causes of sleep disruptions in older adults include a decreased amplitude of the circadian rhythms generated by the SCN (the timekeeper in the brain that maintains circadian rhythms), the degradation of neural signaling in the aging brain, and impairments in melatonin production. More than 40 percent of people over sixty-five report sleep problems. Nighttime sleep is often interrupted by frequent awakenings (sleep fragmentation); these interruptions become more frequent in the early-morning hours, and it can become more and more difficult to get back to sleep.
With increasing age, the essential slow-wave sleep stage, a phase of non-REM sleep, is reduced, and early-night REM sleep increases. Restless leg syndrome, the urge to move one’s legs while sleeping, is common in older adults, and this results in increased sleep fragmentation. Disordered breathing, including sleep apnea, is also common and is related to decreased lung capacity, obesity, loss of pulmonary control, and reductions in thyroid function. Sleep disturbance causes memory loss and some physical and psychiatric illnesses, including depression. And it increases the risk of neurodegeneration and mortality.
The problem is that although sleep requirements remain the same as we age, our ability to fulfill them decreases. Older adults are more likely to take naps as a way to compensate for poor nighttime sleep quality. Naps can compensate for poor nighttime sleep, but it’s best to limit them to twenty minutes or you can suffer from sleep inertia—your body may want to stay asleep and a long nap may make you groggier than a short one. You may have read news reports showing that naps are associated with a decreased risk of cardiovascular disease, but there is conflicting evidence on this point and more research needs to be done. The problem is that most studies don’t control for the duration of the naps, or for the amount of nighttime sleep that people are getting. So the studies combine different groups of behaviors, and it’s hard to draw any firm conclusions.
Insomnia comes in many forms—an inability to get to sleep, an inability to stay asleep, poor and inefficient sleep quality, and their annoying cousin, daytime tiredness. As Matthew Walker notes, the past one hundred years of industrialization have interfered with sleep around the world as extended hours of artificial light, and, more recently, the blue light from computers, tablets, and phones, disrupt the melatonin-generating system in our brains. If you’re going to follow the traditional folk wisdom to read a book when you have difficulty sleeping, don’t read an electronic device that emits blue light—it can reduce melatonin by up to 50 percent.
Hypersomnia is the opposite of insomnia—sleeping too much. Some unfortunate people can have both at the same time, whereby they sleep too much for a day or two, then stay awake for a night or two, repeating a cycle. Such cycles are unhealthy, and often fueled by drugs, alcohol, and caffeine.
Hypersomnia can be the result of a degenerative neural disease or depression, or it can result from the more organic cause of increased sleep fragmentation among older adults: Multiple awakenings during the night can lead to poor sleep quality, which fails to restore the homeostatic balance of sleep-wake cycles, and so our bodies crave more and more sleep. Similarly, obstructive sleep apnea causes sleep fragmentation and can lead to hypersomnia. One common cause of hypersomnia is drug use, particularly benzodiazepines (such as Valium or Ativan), anxiolytic medications, antipsychotics, antihistamines, and antiepileptics.
The relationship between hypersomnia and depression is complex. Depression leads to a modulation of brain chemistry that could cause us to want to sleep more. Yet sleeping more, even in the absence of depression, alters the balance of the wake-up chemicals, the body’s own “uppers,” and so can lead to depression. And antidepressants often have a paradoxical effect. Instead of motivating a get-up-and-go feeling, many people are impelled to lie down and sleep . . . and sleep and sleep. Remember David Anderson’s warning: Your brain is not simply a bag of chemicals. Introducing what seems to be a desirable change in brain chemistry, such as increasing serotonin or norepinephrine availability, can have unanticipated consequences.
Treatment for hypersomnia involves slowly removing any prescription drugs that may be causing excessive sleepiness, avoiding alcohol, and resetting your sleep cycle. When that doesn’t work, modafinil or armodafinil upon awakening is generally safe, is tolerated well, and helps to maintain daytime wakefulness without causing jitters, nervousness, or sleep difficulties at night.
Menopausal symptoms last seven and a half years on average, and for some women symptoms last significantly longer. Salient among these are vasomotor symptoms, which include night sweats, hot flashes, flushes, and vaginal dryness. These vasomotor symptoms can be a direct cause of sleep disturbance, or sleep disturbances can occur independently, from any of the variety of factors already mentioned. A meta-analysis of more than fifteen thousand women showed that sleep improvements occurred with menopausal hormone therapy (MHT, also known as hormone replacement therapy, HRT or simply HT) for women who had vasomotor symptoms, but hormone therapy did not improve sleep quality for women who had sleep disturbances due to other reasons. Hormone therapy involves the administration of estrogen, either alone or with progesterone. There are different dosages, formulations, and routes of administration available, and their effectiveness varies.
Hormone therapy remains controversial because, on the one hand, if it helps sleep quality, it can fend off the long list of diseases associated with sleep impairments. On the other hand, there are credible—but not definitive—reports of risks associated with hormone therapy, including increased risk of breast cancer. I’ve found the literature to be a confusing mess, so I reached out to Sonia Lupien, a specialist in hormone replacement therapies at the University of Montreal. We went out for coffee at my favorite local coffeehouse (where they roast their own beans), and I asked her what to make of all of this.
I would really like to give you a clear answer on this one . . . but this is exactly where we are at this point, i.e. in the middle of nowhere! On one side we have the Women’s Health Initiative [WHI] study that showed increased risk of breast cancer in women using hormone therapy and on the other side, we have other studies stating that it is not that bad, we just have to start hormone therapy later in life (and not at forty years old like some did in the past) and all should be ok. Members of the public are still stuck in the middle.
A review of where we are at by Rogerio Lobo of Columbia University Medical Center, published in the Journal of Clinical Endocrinology and Metabolism, says that
in the 10 years since WHI, many women have been denied hormone therapy, including those with severe symptoms, and . . . this has significantly disadvantaged a generation of women. Some reports have also suggested an increased rate of osteoporotic fractures since the WHI. Therefore, the question is posed as to whether we have now come full circle in our understanding of the use of hormone therapy in younger women.
Lobo goes on to point out some flaws in the study and in the way in which it was reported in the press. Although hormone therapy did increase the risk of breast cancer, the likelihood of getting breast cancer still remained extremely rare, and this was swept under the rug. Also not revealed in the initial reports was that women in their fifties who began hormone therapy had a 30 percent reduction in mortality. Lobo concludes,
The current data, particularly with estrogen alone, are highly supportive for a prevention role in reducing fractures, coronary heart disease, and mortality in younger women who initiate therapy close to menopause. . . . We need to individualize therapy in those women with symptoms, with the view that in young healthy women, we probably have come full circle, and a role for hormone therapy in prevention may at least be entertained.
With aging, men undergo a kind of menopause called andropause, concomitant with reductions in testosterone levels. This can lead to hot flashes, night sweats, enlarged breasts (gynecomastia), loss of strength, memory impairment, depression, cognitive decline, changes in sexual function, and disruptions in sleep. Whereas in women menopause means the end of fertility, this is not so in men, who may remain fertile into their eighties and nineties, despite reductions in androgens. Hormone replacement therapy for men consists of testosterone administration. Side effects are minimal as long as testosterone levels are kept within the normal physiological range. For men with prostate cancer, the research on hormone therapy yields contradictory results and is still in a state of confusion: Some studies show that hormone therapy feeds prostate cancer; others show that it is preventative. Add to this the conjecture that most men over the age of seventy-five are developing some form of prostate cancer, even if asymptomatic and undiagnosed, and you’ve got a real problem trying to figure out what to do. Some men fear cancer more than anything else; others fear that andropausal symptoms will impair their lives significantly enough that they seek to do something about it. These quality-of-life issues are very personal and difficult to sort through without professional guidance. Like the confusion with hormone therapy for women, the best advice for men is to educate yourself and consult with a doctor you trust.
Caffeine can disrupt sleep, but not in everyone. My friend Max Mathews, the computer music pioneer, used to drink eight cups of strong coffee every day, and he’d have one right before bedtime. He lived to be eighty-five, which doesn’t seem so old today, but for someone born in 1926 it’s extraordinary. If I drink a cup of coffee before bedtime, I’ll be up all night. So clearly it affects people differently, and intrepid geneticists have determined that genetics plays a role in caffeine metabolism and tolerance, and they’ve begun to identify some of the genes through studies of twins.
Caffeine breaks down in the body to paraxanthine (80 percent) and to theophylline and theobromine (16 percent). Theophylline is also present in tea, and theobromine is present in chocolate.
Adenosine is a somnogen—a sleep-promoting chemical in the body. The stimulant effects of caffeine and its metabolites (theophylline and theobromine) occur because they block adenosine receptors in the brain, and this blockage promotes sleeplessness. Incidentally, the principal chemical in marijuana, delta-9-THC, increases the level of adenosine in the basal forebrain, leading to sleepiness, although there are other ingredients in marijuana that can keep some people awake. It all depends on the interaction of your particular adenosine and cannabinoid receptors. In most stoners, marijuana use ultimately leads to sleep.
On average, caffeine increases sleep latency, the amount of time it takes people to fall asleep after lying down and deciding they want to sleep. It also reduces total sleep time and quality of sleep. Caffeine can reduce melatonin secretion levels by 30 percent. Caffeine also shortens stage 3 and 4 sleep, the most restorative phases, and reduces the amplitude of slow-wave delta band brain activity. Delta wave activity is a reliable indicator of how much sleep need we have. Because caffeine blocks adenosine receptors and attenuates delta waves, sleep homeostasis could be affected, meaning that the cues your body normally uses to go to sleep and stay asleep are disrupted at a molecular level.
I mentioned melatonin in Chapter 8—here’s a bit more about it. Melatonin is a naturally occurring hormone in the body, secreted by the pineal gland during the dark hours of the day, typically a couple of hours before bedtime. It is also produced in other parts of the body. In the retina it is believed to have protective effects on photoreceptors. In bone marrow, it functions as a scavenger of free radicals and enhances immune function, reducing oxidative damage and protecting against iron overload and deterioration in these highly vulnerable cells. In the gastrointestinal tract, melatonin heals and protects against disorders and is being used experimentally as a treatment for gastric cancer, reflux esophagitis, peptic ulcers, ulcerative colitis, and intestinal ischemia/reperfusion.
Melatonin is also widely found in the plant kingdom, where it regulates day-night bio-cycles and acts as a scavenger of free radicals. In tomatoes, for example, it helps to protect the components of photosynthesis. In peas and red cabbage that are grown in copper-contaminated soil it enhances their tolerance and survival rates. This makes melatonin a very old chemical compound that, through evolutionary history, found expanded functionality in mammals.
The American Academy of Sleep Medicine recommends the timed use of melatonin supplements to promote adaptation to new time zones or to help individuals having trouble sleeping for other reasons (such as age-related disturbances of the sleep-wake cycle). Melatonin taken in midafternoon (in conjunction with avoiding blue light) will advance the circadian clock, causing the body to think that nighttime has come early. The effect is somewhat mild, certainly not as powerful as a sleeping pill, but for many, this gentle nudging of the clocks is enough to promote sleep. As Johns Hopkins University sleep researcher Luis Buenaver says, “Your body produces melatonin naturally. It doesn’t make you sleep, but as melatonin levels rise in the evening it puts you into a state of quiet wakefulness that helps promote sleep.”
Melatonin levels in the blood are highest in young people (55–75 pg/ml) and start to decline after the age of forty, with the fastest decrease found from sixty years of age onward, reaching very low levels in the elderly (18–40 pg/ml). New research suggests that melatonin may have protective effects against many cancers, which may be part of the reason that as people age—and melatonin levels go down—they are more susceptible to cancers.
Given the time-dependent nature of hormonal release schedules that are governed by the circadian clock, what is the most important thing about sleep? To go to bed at the same time every night and wake up at the same time every morning. Even on weekends. This may mean forgoing late parties if you’re an early bird, or missing early-morning events if you’re a night owl. Although few of us lived this way in our twenties and thirties, by the time you reach sixty-five or so, you may begin to notice that inconsistency has become even more punishing. Even a slight change to the schedule—staying up an hour later than usual, for instance—can affect your memory, alertness, and immune system for days. Adrian de Groot, the Dutch chess master and psychologist who performed some of the most famous experiments on the minds of chess players, lived to ninety-two. To maintain his mental acuity during the last twenty-five years of his life, he was fastidious about going to bed and waking up at the same time every day.
Follow these steps. They apply to people of any age, but as we get older it can become increasingly necessary to be strict about them.
Start getting ready for bed about two hours before sleep time. Stop watching TV, using a computer, tablet, or smartphone, or other sources of blue light (daylight wavelengths) that could act as a zeitgeber for the pineal gland and cause your brain to produce wake-up hormones. Do something that helps you relax—a warm bath, reading, music listening, whatever works for you.
Ensure that the room you sleep in is completely dark. If you have a clock, charger, or other device that emits blue light, cover it up. Make sure that your curtains block out both daylight and any artificial light that may come into the bedroom.
Sleep in a cool room if possible.
Help to keep your sleep and wake cycle synchronized properly by getting sunlight in the morning—even on a cloudy day, the wavelengths you need can activate the pineal gland. A simulated dawn (blue-light) lamp for fifteen to thirty minutes in the morning can help.
Write in a journal before bedtime. Recent research shows that it helps you to relax and can improve memory. It’s especially effective if you write a quick to-do list for tomorrow. Worrying about incomplete future tasks is a significant contributor to difficulty falling asleep.
Don’t rely on sleeping pills for more than one or two nights. The sleep they induce is less productive and less restorative than natural sleep.
Go to bed at the same time every night. Wake up at the same time every morning. If you have to stay up late one night, you should still get up at your fixed time the next morning—in the short run, the consistency of your cycle is more important than the amount of sleep.