your
sleep
brain rule
For clear thinking, get enough
(not too much) sleep
No one looks back on their life and remembers
the nights they had plenty of sleep.
—Anonymous
I’ve reached the age where happy hour is a nap.
—Anonymous
“I SLEEP!” SUSANNAH MUSHATT JONES exclaimed, bursting with laughter. She was responding to a reporter who had just asked her a familiar question: the secret to her long life. She also mentioned eating scrambled eggs, grits, and four strips of bacon, a breakfast she’d had every single morning that she could remember.
She had a lot of mornings from which to choose. Jones turned 116 years old in 2015, the last living American born in the nineteenth century and, briefly, the oldest woman alive (she died in 2016). Though she had no children of her own and was married only once—and only for a short while—she had more than a hundred nieces and nephews to spoil. And spoil she did. Ms. Jones put her first niece through college—a terrific investment that grew to include a doctorate—and the niece returned the favour by penning her aunt’s biography. Extending her generosity, she started a scholarship fund for African American students. Born to sharecroppers in Alabama, Jones spent most of her life working as a nanny and live-in housekeeper in New York.
Except perhaps for the bacon, Jones lived what most of us would call a healthy lifestyle. She never smoked, didn’t drink, and saw her physician several times a year. Remarkably for this day and age, she took only two medications—for blood pressure—and a ream of multivitamins. She was active on her building’s tenant patrol team until age 106. The source of her exclamation? She slept ten hours a night, plus naps.
I’ll come right out with it: there’s more bad news than good news in this chapter. But a little bit of the bad is preventable if we can, like Jones, practise great sleep habits. To understand the effects of sleep on our quality of life in old age, we have to know a little bit about how sleep works, why we sleep, and how sleep changes over time. In this chapter, we’ll also talk about the cognitive effects of not getting enough sleep, and finally how to get the best sleep you can. Some scientists believe that sleep, if you’re interested in optimising health in both body and brain, is the single most important experience of the day.
Or should I say, night.
Night owls and early birds
Many people are surprised to discover three things about research on sleep:
These San Andreas–size gaps in our understanding are surprising, given how much experience humans have with sleep. By the time you’re eighty-five, you’ve spent 250,000 hours in slumber-land, about twenty-nine years of your life.
One of the most surprising characteristics of sleep is its hyper-individuality. Many variables affect sleep, making it pretty tough to tell a consistent story.
Country of origin is one example. People in the Netherlands, on average, sleep eight hours and five minutes each night. People in Singapore sleep seven hours and twenty-three minutes. This is how much sleep they get. Is that also how much they need? Currently, no one knows.
Sleep also varies by chronotype, which is the natural sleep/wake cycle you experience when you smash your alarm clock and wake up when you feel like it. Some people function best if they hit the sheets at 9:30 p.m., then wake up with the morning’s overachievers. Some function best if they start sleep at 3:00 a.m. and wake up with the afternoon’s rock stars. Other variables include stress, loneliness, and how many sleep-altering substances you regularly consume (coffee lovers?) during the day.
Perhaps the biggest single source of variability is age. Newborns sleep a leisurely sixteen hours a day. Older adults usually get less than six. Even these numbers have to be taken with a giant boulder of salt, however. Some people need five hours of sleep a night. Others can’t get by with less than eleven. There was a seventy-year-old British woman who claimed to need only sixty minutes of sleep a night. She was wrong. When sleep scientists examined her over a five-night period, the number was sixty-seven minutes of sleep per night. She showed no obvious behavioural or cognitive disabilities, no sleep-deprivation deficits. While that’s unusual, the variability between people is not.
Ease of sleeping is variable, too. More than 44 per cent of Italian seniors report serious difficulties sleeping, as do 70 per cent of the elderly in France. About 50 per cent in the United States and Canada report dozing difficulties. Their problems are divisible into two categories. The first involves getting to sleep, something researchers call sleep onset latency. The second involves staying asleep, something all of us call annoying.
One thing we can say for certain is that sleep quality diminishes with age. To understand how that happens, we first have to understand how sleep works.
The sleep cycle is born of conflict, like two teams competing in the ultimate soccer match: they play each other twenty-four hours a day and don’t stop until you’re dead.
The sole function of one club—let’s dress them in light uniforms—is to keep you awake. This team has lots of talent at its disposal, hormones and brain regions and fluids playing together with a single goal: to keep your eyes open during the day. We collectively call Light Kit the circadian arousal system. Circadian, a word coined in 1959, literally means “about the day.”
The other club is composed of a set of biological processes with the opposite goal. Their entire function is to make you sleep. This team—let’s dress them in dark uniforms—also involves hormones and brain regions and fluids, but their job is to put you to bed and keep you there for hours. We collectively call Dark Kit the homeostatic sleep drive.
These teams play against each other every minute you’re alive, probing, skirmishing, interacting with the enthusiasm of Premier League fans. There’s never a tie game, and the play is highly uneven, each team dominating only at certain times of the day. During daylight, the circadian arousal system controls the field. At night, the homeostatic sleep drive rules. Though this give-and-take occurs in twenty-four-hour cycles, it is remarkably independent of sun and sky. The oscillations would take place even if you lived in a dark cave, though then it tends to cycle in about twenty-five-hour chunks, adding an hour for reasons absolutely nobody understands.
Catching the wave
This neurological soccer match—technically called opponent-process theory—can be characterised by brain wave patterns. Brain waves are observable using the hairnet-like EEG device that detects the brain’s surface electricity.
The day starts with light uniforms in full control, your brain broadcasting an electrical pattern called beta waves. At night, when the dark uniforms start perking up, these betas are replaced with more relaxed alpha waves, indicative of drowsiness. Eventually you’ll be coaxed into a good night’s snooze. During the process, your brain descends through three full stages of increasingly deep sleep, the bottom stage occurring about ninety minutes after you’ve started. This deepest of sleeps, characterised by large, lumbering brain waves termed deltas, is called slow-wave sleep. It’s extremely difficult to awaken somebody who is resting on the bottom.
But not impossible. In fact, after an hour and a half, your brain begins to do it for you. The big, slow delta waves give way, and you ascend backward up through the sleep stages, meaning you get “less sleepy.” For reasons nobody understands, your eyes signify this arousal by moving back and forth rapidly, a stage appropriately known as REM-1, for rapid eye movement—one. This REM sleep is qualitatively different from deep sleep, logically termed non-REM sleep. At this stage, you can be more easily awakened.
But if all goes normally, you won’t be. The dark uniforms will resume their dominance, and you will descend through another three stages of increasingly deep sleep. The large, soothing deltas soon return, allowing you to spend a blissful sixty minutes at the bottom.
That is hardly the end of the arousals, however. The reason it’s called REM-1 is because it’s only the first of several stages you’ll experience that night. You’ll typically encounter four more REM events before the night is over, each followed by its own set of deep-sleep dives. Only after the fifth one will the light uniforms pick up their daytime hyperactivity, wresting the field from their opponents and letting you start your morning. This oscillating never pauses for a commercial break. It never stops wanting to wake you in the morning, however much you may resist it, or wanting you to go to sleep at night.
That is, until you start getting older. The teams still want to keep their rhythms, but they find it increasingly hard to do so.
That’s the how of sleep. What’s the why? The answer seems as obvious as a bad mood. When you don’t sleep, you get cranky and irritable, you can’t find your car keys or your patience—and most of all, you feel tired. Sleep must involve energy restoration, right?
Wrong. Or at least partly wrong. Bioenergetic analysis shows the energy savings during sleep is only about 120 calories, the same as a bowl of soup. And your brain is mostly to blame for this. It’s the power hog of the body, taking 20 per cent of the energy you consume and required to remain active 24/7 to keep you alive. Saving the energy found in a cup of broth is not impressive. Restoration isn’t why we sleep.
Then why do we? From an evolutionary perspective, it’s nuts to flatten someone as weak as we are for even ten minutes in the arid plains of eastern Africa, especially in the dark. Yet we regularly stretched out on the savannah, paralyzed for hours, during the same shift normally scheduled for active leopards. Big price to pay for 120 calories.
Only recently have researchers found light at the end of our contradictions. The insights have profound implications for the ageing brain. This chapter describes two of the biggest breakthroughs in our understanding of why we sleep.
We sleep to learn (breakthrough one)
The first breakthrough comes mainly from memory research. As you know, your daylight brain is busy recording your various daily activities. Some are forgettable, some are important, and some need time for future processing. Your memory systems are constantly engaged. At least two regions are involved.
The first is the cortex, those layers of world-class intelligence surrounding the brain like wrapping paper. Or a diploma. The second is the hippocampus, that sea-horse-shaped structure we’ve mentioned often, deeper inside your brain. These two regions form electrical connections with each other during memory formation, communicating like texting teenagers. This activity holds the memory fragments in place until they can be processed at a later date.
What later date? Scientists now know that it means “later that night, during slow-wave sleep.” Throughout the deepest slumber, your brain reactivates the memories laid down during the day, the ones marked for later processing. It then repeats their electrical patterns thousands of times, which strengthens connections, consolidating the information they hold. It’s called off-line processing. If you can’t perform this important reactivation, you can’t store anything long term.
Tucked inside these data is a bombshell of a finding. You need to sleep not to rest but to learn. Nighttime is the perfect time for it, when there’s little competing information bombarding your brain for attention.
As research continues, it has demonstrated that sleep aids other functions, from digestion to keeping your immune system humming along. Slowly, we’re beginning to understand why you need to sleep. It’s not because you need to rest. It’s because you need to reset. When resting doesn’t function properly, resetting becomes a challenge.
Which, unfortunately, is exactly what happens when you age.
Slow-acting acid
There’s a box I keep downstairs, and when I see it I feel despondent. It contains videos of our kids’ childhoods.
Why despondent? Not because of the contents—those videos hold some of the most precious memories I have—but because of how the contents are stored. The videotapes are VHS. If I leave the tapes in their current location, I only recently discovered, I might as well store them in slow-acting acid. They’ll begin chemically eroding, losing information with the passage of time. This natural degradation doesn’t occur immediately and is subject to environmental conditions such as humidity and temperature. But information will get lost—fragmented would be more accurate—if I don’t do something. Stored at sixty degrees (assuming reasonable humidity), significant fragmentation will become observable after sixteen years. Increase the temperature to seventy degrees, and loss becomes noticeable in eight. The oldest of our tapes is nineteen years old. See why I feel despondent?
Natural erosion through time is what ageing is about, whether you’re talking about information stored on magnetic tapes or information stored as cognitive processes. And sleep processes are not immune. In short, they erode, like a VHS tape in your head. Your sleep becomes fragmented.
Specifically, the amount of that memory-inducing, garbage-collecting, completely useful slow-wave sleep (SWS) decreases as you get older. In your twenties, you spend about 20 per cent of your nighttime bathing in its healing breakers. By the time you reach seventy, you spend about 9 per cent.
To illustrate these changes, consider this comparison between two sleepers during a typical night’s rest.
Let’s say a kindly grandmother and her twenty-year-old grandson, Noah, go to bed at the same time, around 11:00 p.m. In ten minutes, the grandson has started floating smoothly through the stages of non-REM sleep, surfing the slow waves just before midnight.
Grandma does this, too, but her transit is anything but smooth. She descends the same stages, but upon arrival at the second non-REM stage, she suddenly comes back for air, reawakening around 11:30. Now she has to start the whole process over again. Grandma gets to the same midnight SWS checkpoint, but, unlike Noah, she doesn’t stay there long. She comes back up around 12:30 a.m., awakening a second time, and once again has to start the whole process over. She’ll ping-pong like this all night, her last visit to the SWS spa occurring around 2:30 a.m., if she gets there at all. Her experience is called sleep fragmentation. Noah, conversely, has cycled smoothly through the entire process, experiencing four to five cycles of non-REM/REM sleep, with four luxurious swims through the slow-wave ocean. He stays asleep the whole night.
What’s controlling the sleep experience of both Noah and his grandmother? To explain that, we are going to take a visit to Boulder, Colorado.
The grip of a tiny clock
Buried in the hills of Colorado lies a machine capable of more destructive mayhem than all the world’s nuclear weapons combined. Here’s what would happen if this technology stopped working: civilisation would be held hostage. Police, fire department, and emergency medical dispatch communication systems would suddenly go silent. Electrical grids would desynchronise, then overload, creating catastrophic power outages all over the world. Wall Street and attendant global financial sectors would seize up, as if epileptic, and high-speed market transactions would freeze in their digital tracks. Satellite communications would be disrupted, meaning airplanes midflight would no longer know where they were. Neither would you if you were using your cell phone’s GPS to get around. That’s okay; the phones wouldn’t work anyway, except for your previously downloaded copy of Angry Birds. Civilisation would come to a crippling, grinding, blinded halt.
What doomsday device could possibly hold such ransom over the modern human experience? The answer seems mundane. What’s buried in the hills of Colorado is a clock, driven by an engine the size of an atom. The device is the NIST-F2, the world’s most accurate atomic clock. It uses the natural vibrations inside a cesium atom to determine exactly what a “second” is, a number required to synchronise most of the world’s infrastructure. As long as it functions, civilisation flourishes. This powerful chronometer loses one second in three hundred million years.
Buried deep inside your brain is a little patch of neurons—only about twenty thousand cells strong—known as the suprachiasmatic nucleus. The SCN, located several inches behind your eyes, contains the master pacemaker of the body, the cesium clock of human experience. Its natural rhythms are generated—and measurable—through electrical outputs, hormonal secretions, and gene expression patterns. The rhythmic instincts of these cells are so strong, you can excise them from a brain, disperse them into a dish, and they’ll still pulse in rhythmic twenty-four-hour cycles. They control what scientists term the human body’s circadian system.
And they are the reason it’s harder than it used to be for you to get a good night’s sleep.
The circadian system works as independently as an entrenched dictator. Yet its scheduling is subject to tweaking—which is one reason we have some control over our sleep. The SCN receives information about the time of day directly from the eyes, along neural trunks called retinal projections. This helps it synchronise its rhythmic output to the turning of Earth. The SCN then uses this information to make you drowsy during the night and aroused during the day. (This function isn’t the only factor controlling sleep—core body temperature is also important, for example—and it’s not the only thing over which the SCN has sway. The stress hormone cortisol is under tight circadian control. So is digestion. Synchronisation occurs because many other biological “sub-clocks” are scattered throughout the body, all communicating with the SCN, like cell phones responding to a cesium clock.)
How does the SCN keep a grip on sleep? This talented nerve knot interacts with many brain regions, including the brain stem, which does most of the heavy lifting in generating sleep cycles. The SCN exerts its rhythmic will via hormones, including its franchise player, melatonin. The hormone is made off-site, a few inches behind the SCN, in a pea-size organ called the pineal gland. During the night, the SCN turns the pineal spigot to “on” and melatonin floods the blood. It’ll circulate all night long, not seriously reducing its levels until about 9:00 a.m.
Losing our rhythm
Why does sleep shift from smooth to fragmented as the years roll by? Researchers have uncovered several interesting alterations that occur in elderly brains, all involving circadian rhythms, most involving the SCN.
The ageing process does not affect the number of neurons in the SCN. Or its overall size. If you could magically remove the SCN from grandmother and grandson, inspecting only outer structure, you couldn’t tell which was which.
That’s not true with inner structure. Most of the rhythmic systems associated with the SCN are altered with ageing. Electrical output changes. The ability to secrete pace-setting hormones diminishes. The expression of rhythm-inducing genes in the SCN declines. All of these have measurable effects on sleep and arousal, specifically targeting levels of melatonin and cortisol. Researchers believe these changes reverberate throughout the body—primarily, of course, in the ability to get a good night’s rest. That’s why Grandma can’t sleep through the night while her grandson Noah glides through it like syrup.
Does this matter for Grandma? Does sleep fragmentation hurt cognition? Researchers used to say yes. The sleep cognition hypothesis postulated that most age-related cognitive deficits could be laid at the feet of sleep loss. But there’s a reason it was called “hypothesis.” Close investigation revealed that the sleep cognition hypothesis was way too simplistic, bordering on being wrong. Researchers originally thought data that applied to younger populations were transferable to older populations. Two examples will suffice to show the error of this oblique form of ageism.
Memory
Like a song you just can’t keep out of your head, the brain replays over and over again at night what occurred in the daytime. We mentioned this overplaying a few pages ago, showing it assists long-term memory consolidation in the human brain. Later investigations showed the boost occurred only for people younger than age sixty. This is thought to occur because of age-related changes in a network of the brain called the corticostriatal network. This network consists of loops that straddle both hemispheres of the brain and are usually involved in mediating feelings of goal-directed behaviours. In older individuals, these loops are just not as active. When researchers assessed off-line processing skills in seniors, using the tests given to younger populations (looking for memory pick-me-ups), they showed none of the benefits less mature crowds enjoyed.
Executive function
Sleep loss is associated with the loss of a number of socially lubricating behaviours, including executive function. That comes from sleep deprivation studies done mostly with willing American undergraduates, and many researchers simply assumed that older populations would show similar deficits. They don’t. Sleep deprivation studies in older populations showed no deficits in executive function over baseline—including measures of impulse control, working memory, and attentional focus.
Why wouldn’t sleep loss hurt older people? Some researchers believe cognitive deficits due to natural ageing don’t get any worse because they can’t get any worse. The damage has already been done. They also can’t get any better, for the same depressing reason. This concept is called the floor effect. Cognitive deficits reach a floor below which no travel may be possible.
The situation isn’t hopeless, even if flooring turns out to be the wrong explanation. A lesson from the Old Testament points us in the right direction.
An early start
You might recall biblical Joseph, penultimate son of patriarch Jacob, second in command of the sprawling Egyptian empire. He got the position because of the strangest job interview in the world, where he made known his ability to interpret two of Pharaoh’s troubling dreams. The first dream involved cows, seven lazy, obese, beautiful bovines, emerging from the Nile to graze on nearby grass. Seven ugly cows soon follow them out of the river (the Bible quotes Pharaoh as saying, “I had never seen such ugly cows!”), lean and scrawny and apparently scrapping for a fight. Straight out of Stephen King, the lean cows turn predatory and carnivorous and attack their fattened colleagues, gobbling them up. The second dream followed the same horror script, but with different characters (involving murderous stalks of wheat). Joseph correctly interpreted these dreams as a warning. Egypt would have seven years of bountiful harvest, followed by seven years of famine. If the people were to survive, they needed to work the fields early and store sustenance for the coming not-so-rainy days.
The job was his.
Here’s the lesson for us: saving up for the not-so-rainy days hints at how to treat the effects of age-related sleep fragmentation. If you want to diminish cognitive decline in old age, you must start accruing good sleep habits in middle age.
That’s what sleep researcher Michael Scullin thinks. He and a colleague reviewed nearly fifty years’ worth of literature on sleep to look for patterns, and they summarised their findings this way: “Maintaining good sleep quality, at least in young adulthood and middle age, promotes better cognitive functioning and serves to protect against age-related cognitive declines.”
Storing up good habits now pays dividends when the cognitive famine arrives.
We sleep to sweep (breakthrough two)
Fairly recently, scientists have discovered another, less glamorous function that comes online when you go off-line: garbage disposal.
My research consulting and speaking activities occasionally find me in strange hotels, unable to sleep. From my room, I can watch a given city’s night shift: garbage collection trucks loudly rumbling through empty streets, taking waste to landfills; street cleaners rumbling even louder, pushing dirt to the curb. The brain needs garbage collection and street sweeping, too. With all the energy the organ consumes during the day, a lot of toxic waste builds up in its tissues. This needs to be flushed away, just as city garbage must be removed and streets cleaned.
Beautifully, your brain has just such a system. Actually it has many drainage systems. Acting like their urban counterparts, many become active at night. One of them is called the glymphatic system. Here’s how it works:
Your neurons are bathed in salt-water fluids, similar to the ocean from which they originally sprang. Waste that accumulates in the brain is dumped into these fluids, like irresponsible companies dumping pollutants into nearby streams. Happily, the glymphatic system, composed of cells and molecules and channels, works like a well-funded EPA. It can isolate the junk, remove it from the fluid, and siphon it off to your bloodstream. The toxic waste is removed from the brain, and you pee it out in the morning. This convective system operates during slow-wave sleep, the same stage in which learning occurs.
The same stage that we get less of as we age.
When toxic waste builds up
Even in New York City, a town legendary for labor disputes among its sanitation engineers, the garbage strike of 1911 stands out like rotten meat.
Two organisations, garbage collectors and street cleaners, pressed the city for better working conditions. Officials refused their demands, triggering the strike. It began slowly, with garbage and street debris removed sporadically. As refuse piled high and roads clogged, the city grew increasingly dysfunctional. Officials responded by hiring strikebreakers, who were immediately physically assaulted by the striking workers. Garbage piles piled higher, blocking traffic, creating an incredible stink and a deadly health hazard. To make matters worse, a freak snowfall blanketed the garbage-choked streets right in the middle of the strike. It became in everybody’s best interest to get back to work, flush the city clean. That happened a month later, after a great deal of violence, including a few tragic deaths.
Sporadic removal of growing garbage lies at the heart of another conflict, one that takes place in our head during SWS. As you age, your sleep becomes fragmented, and you miss out on this necessary type of sleep. Wear and tear on your SCN—the brain’s pacemaker for the sleep/wake cycle—causes the fragmentation. Without slow-wave sleep, researchers believe, the cleaning crew begins to go off-line and waste removal becomes increasingly sporadic.
Just like in the garbage strike of 1911, toxic stuff accumulates. Researchers believe this toxic waste buildup begins damaging brain tissue beyond a certain threshold. The damage includes the sleep apparatus itself, which of course results in more fragmented sleep, less slow-wave slumber, and more damage. Some sleep researchers hypothesise that this damage eventually results in behavioural changes, including cognitive decline and dementia. To summarise, a dysfunctional SCN reduces slow-wave sleep. This leads to only sporadic garbage removal, leading to neural damage.
It’s only one idea, and even it suffers from something of a chicken-and-egg issue. Consider that this vicious cycle starts with a dysfunctional SCN and ends with dementia. It could be that the molecular garbage pile begins accumulating for reasons other than sleep loss (a genetic origin is a distinct possibility). And then it isn’t until toxic waste reaches that certain toxic threshold that the SCN is rendered dysfunctional. This triggers the rest of the steps. At this stage of our understanding, researchers are not sure if the SCN starts the ball rolling initially or jumps in later in the game.
Where does this hypothesis originate? Researchers have known for years that a chronic lack of sleep is a risk factor for many neurodegenerative diseases—including Parkinson’s, Huntington’s, and Alzheimer’s. Consistent with this epidemiological observation, it was noticed years ago that jet-lagged flight attendants (especially those logging long-haul international flights) have an unusual amount of hippocampal atrophy, a telltale sign of Alzheimer’s. Eventually researchers showed that circadian disruptions (in any profession) promote system-wide inflammation and uncleared toxic waste.
Those convinced that the amyloid hypothesis explains Alzheimer’s use this hypothesis to bolster their claims, and for this reason: it is now abundantly clear that the inability to flush out the toxic amyloid fragment Aß is what really causes the damage in Alzheimer’s. With increasing sleep loss, the fragment appears to hang around longer than it should. That’s why lack of sleep is a risk factor for Alzheimer’s. Add in the fact that the glymphatic system dramatically slows whenever you awaken and a consistent story emerges: Aß has no way of being consistently removed. Dementia is the hypothesised result.
This alone provides a powerful reason to get a good night’s sleep, and at any age. But it’s hardly the only one. The length of your life and your mental health are other solid arguments for why sleep is important, and it is to these issues that we turn next.
The bedtime story that’s just right
For surprisingly professional reasons, many scientists love the Goldilocks story. It gives us a way to illustrate an interesting tendency common to many of the biological processes we study. Behavioural processes, too.
My favourite Goldilocks variant comes from the old Rocky and Bullwinkle Show. This version told the story of blond Tussenelda Woofenpickle (whose nickname was “Goldilocks,” intoned the narrator, because of her golden curls). Goldilocks gets lost in the woods and finds the Bear Family cabin populated by Mama, Papa, and Little Oswald. Only Oswald’s stuff, from porridge to rocking chair to bed firmness, is “just right.” The parental units’ stuff either overshoots or undershoots Goldilock’s delicate sensibilities. Edward Everett Horton’s stentorian voice-overs, accessorised in a pseudo-British/Brooklyn accent, give the episode a satirical, false gravitas. After all these years, it’s still fun to watch.
Still instructive, too. I discuss here the optimal number of hours you need to sleep to get the best shot at the highest quality of life. And the highest probability of living the longest while you’re busy enjoying this quality. As you’ll see, the data follow an inverted U shape: two extremes that don’t suffice and a sweet spot in the middle that’s just right.
Studies show that sleep disruptions aren’t just inconvenient. They’re deadly. Not getting a specific amount of sleep affects how long you live. From studying thousands of people (21,000 Finnish twins, actually), we can even say what that amount is.
Here’s the bottom line: you need to get between six and eight hours of sleep every night, no more and no less. If you get less than six hours, mortality risk rises 21 per cent in women, 26 per cent in men. If you get more than eight hours, mortality risk rises 17 per cent in women, 24 per cent for men. You have to have the “just right” amount of sleep to optimise both quality and quantity of life. Sound familiar? This is where our Goldilocks discussion becomes relevant.
The mortality risk is referring to any cause of death. But not surprisingly, the usual suspects are the ones associated with old age: stroke, heart disease, blood pressure issues, type 2 diabetes, obesity. What is surprising is that these numbers are actually lower than they are for younger people. Young men, for example, see a 129 per cent greater mortality risk with sleep loss. How does that work, and why is there a difference between the generations? Currently, we have no idea.
And you’ll have to take these figures with a grain of statistical salt. Yes, the data are solid. However, as you may remember from high school math, statistics don’t apply to individuals. Sleep duration requirements still vary from one person to the next.
I mentioned near the beginning of this chapter that many seniors, across a range of countries, report difficulty sleeping. That’s important for several reasons. One sleepless night can leave you grumpy, but several in a row can leave you cognitively impaired. Everything is affected, from memory functions to problem-solving abilities.
Worse, there’s a deeply troubling association between consistent sleep loss and mental health. Seniors taking more than thirty minutes to fall asleep have an increased risk for anxiety disorders, and for a reason probably familiar to you. They begin reviewing all their troubles at bedtime, experiencing an endless film loop of worry, replaying the same concerns over and over again. Though this caustic habit of rumination can afflict any age, old people have uniquely serious reasons to worry. They may be feeling a lack of control over mind and body, especially if medical issues are involved, and uncertainty about finances and relationships. Soon thirty minutes have gone by, and all they’ve got to show for it is a sweaty bedsheet.
Depressive disorders are also linked to increased sleep fragmentation. Seniors who suffer from depression generally fall asleep quickly. They just don’t stay there. Depressed elderly get the worst sleep of all.
Why does this troubled business partnership exist between sleep and mental illness? We have no idea. Though we know sleep and affective disorders are tightly linked, we don’t yet know the direction of the linkage. Fortunately, that hasn’t stopped researchers from trying to figure out ways to help us all sleep better. One who rolled up his practical research sleeves was the late sleep scientist Peter Hauri.
How to get better sleep
Dr. Hauri had a German accent as thick as bratwurst. Swiss by birth, he was blessed with a Matterhorn-size laugh and a mind like a Rolex. He got into sleep research after immigrating to the United States, where he quickly rose to prominence. For years he headed the Mayo Sleep Disorders Center in Rochester, Minnesota.
Some of his research ideas made headlines. He suggested people get rid of their alarm clocks. He encouraged insomniacs never to try to sleep, declaring it just makes them more aroused. And he recommended people keep track of their sleep habits the way some people keep track of their diets. His ideas were eventually codified into the book No More Sleepless Nights. It was for years the go-to book for treating insomnia.
Some of Hauri’s insights, along with more recent findings, are listed below. You need to adapt them to your own situation, however. Hauri would be the first to tell you that everyone’s sleep habits are unique—“like snowflakes,” he once said, undoubtedly with a twinkle in his eye.
1. Pay attention to the afternoon.
Getting a good night’s sleep starts with paying attention to what you’re doing four to six hours before you go to bed. No caffeine six hours prior. No nicotine. No alcohol, either. Alcohol, legendary for inducing drowsiness, is actually a biphasic molecule possessing both sedating and stimulating properties. Drowsiness occurs initially; the stimulating effect much later. When you drink, you spend less time in REM and SWS, especially in the terminating night hours. Exercise has a profoundly positive effect on your ability to sleep, but you want to do it earlier in the day. It’s become evident in recent years that ensuring a good night’s sleep occurs way before you hit the sheets.
2. Create a sleep “terrarium.”
Designate a place in your house where the only activity is sleep. That’s going to be the bedroom for most people. Don’t eat there, don’t work there, don’t have a TV there. Just sleep. (You might do one or two other activities there, but see the above admonition concerning exercise.)
3. Watch the temperature.
People fall asleep ideally around 65 degrees. Make sure the room you just designated as Sleep Central is cool. Install a fan if needed, which is a good idea for another reason. In addition to temperature regulation, it provides steady white noise. That helps many people go to sleep.
4. Create a stable sleep routine.
Go to that cool single-use bedroom of yours at the same time every night. Wake up at the same time every day. No exceptions. If you’re unable to fall asleep in time to get six or seven hours of sleep at first, continue to wake up at the same time, to reset your routine.
5. Pay attention to your body’s cues.
If at all possible, don’t bed down until you’re tired. And if you wake up during the night, don’t turn the experience into an Olympic toss-and-turn fest. If you can’t fall asleep after thirty minutes, don’t stay in bed. Get up and read a dead-tree (non-electronic) book. Especially one that’s boring.
6. Pay attention to light exposure.
Expose yourself to bright light during the day, dim light during the evening. This mimics what our brains were used to experiencing during our sojourn under the vast African skies.
7. Stay away from blue light.
That means laptops, TVs, mobile devices, or anything that radiates at 470 nanometers (the frequency of blue light). That wavelength has been shown to trick the brain into thinking it’s daylight. Arousal follows, and for a logical evolutionary reason. Blue is the color of sky, which the brain historically encountered only in the daytime.
8. Visit lots of friends during the day.
Depression is associated with sleep fragmentation, and social interactions are powerful antidepressants. Social interactions also exert a surprisingly powerful cognitive load, giving the brain a real workout, preparing it for surfing the slow waves later that night.
9. Keep a sleep diary.
This is especially important if you have serious problems sleeping and are considering professional help. A simple version involves documenting when you wake up, when you go to sleep, and your frequency of nighttime awakenings. You can find more sophisticated templates online. (Hauri’s book No More Sleepless Nights also has templates you can use.)
Most of these suggestions are settled law, many coming from Hauri’s work at Mayo. However, everybody’s situation is different. We’ve covered most of the basics, but we’ve neglected certain environmental issues, such as debilitating pain, and all nature issues, such as genetics. But there’s one specific issue I want to address: insomnia.
A few years before Hauri’s death, a protocol was tested with the aim of helping seniors with troubled sleep. University of Pittsburgh researchers developed the protocol, called the brief behavioural treatment for insomnia.
The intervention was simple. Researchers first obtained a “sleep baseline” from each senior. Behavioural and physiological measures included actigraphy (involving a wearable sensor that measures motor activity) and polysomnography (involving recording brain waves, cardiovascular activities, and more). Then the seniors took a mini-class explaining how sleep works, including opponent-process theory. They were introduced to their research task:
1. Subjects were to reduce the amount of time they spent in bed (six-hour minimum).
2. Subjects were to observe a strict adherence to a daily schedule, arising from bed at the same time—even if their previous sleep was of low quality.
3. Subjects were not to go to bed until sleepy, regardless of the time.
4. Subjects were not to stay in bed for long if they had not fallen asleep.
Teaching these ideas took about an hour, with a thirty-minute “refresher course” two weeks later, and the instructors called the seniors a couple of times to check in on compliance. At the fourth week, subjects came back into the lab to retake the tests.
The idea was to get their sleep schedule to run like a watch, breaking the hold insomnia had on these elderly folks.
It seems like a small effort, but don’t let that fool you. Fifty-five per cent of the group who underwent the treatment showed no insomnia by the time they were finished. That’s complete remission, folks, from a formerly very sleep-troubled population. And six months later, many continued to see the positive results: 64 per cent maintained a dramatic improvement in their sleep experiences—and 40 per cent were still in remission from insomnia. What’s interesting about these data is what’s missing. There was no psychiatric counseling. There was no sleep-inducing medication. (That’s a good call. In older populations, the side effects of commonly prescribed sleep sedatives tend to be overwhelming. And sleep gets only marginally better.)
This protocol is a great example of a theme we’ve visited many times: the power of lifestyle changes in combating the negative effects of ageing. “Lifestyle changes” means changes in lifelong habits. So the practical suggestions here, if adhered to closely, have long-term, life-affirming consequences.
So far in this book we’ve talked about ways to improve the quality, and maybe even length, of your life. There’s one question you’ve surely thought about if death is only a decade or two away. Can you arrest the process of ageing? Can you give it a speeding ticket, convince it to slow down, maybe even stop it altogether? We are going to discuss attempts to increase longevity and, in so doing, separate one last time science from science fiction.
SUMMARY
For clear thinking, get enough (not too much) sleep