We'd be thinner, smarter and healthier too, if only we valued sleep more, says Eric Harrison.
We all know the value of diet and exercise for good health, but we almost completely ignore the importance of sleep. Most people in modern industrialised societies now function with poor or inadequate sleep. Just as being overweight is now "normal", in the sense that most people are somewhat plump, it also seems normal to feel somewhat tired most of the time. Isn't everyone?
We certainly need more sleep than we typically get. Research tells us that people under ideal conditions will sleep between eight and nine hours a night like our closest animal relatives, the chimpanzees. A few years ago, William Dement, one of the pioneers in this field, estimated that people now sleep about an hour and half less than they did just a century ago, let alone the millions of years before that. We can also assume that the world is now a lot faster, brighter and noisier than when he made that estimate, and that sleep quality has declined even more in the last decade or two.
Experiments have shown that sleep is more critical for our survival than food and water. Animals, like humans, can last for weeks without food, but deprive them of sleep and they invariably die within days. Conversely, people who sleep well tend to live longer and healthier lives than those who sleep badly.
If we're tired, we easily can flip into a "micro nap" without realising it. Only when a nap becomes longer than a minute or so, do we realise we're not there. When exhausted, we can fall asleep with our eyes open, in bright, noisy surroundings, while performing automatic tasks. Think driving. We can easily travel a kilometre or two on the freeway during a micro nap. According to some estimates, falling asleep at the wheel kills as many people as alcohol does - and that's hundreds of thousands a year. By the way, the telltale sign of a sleep-induced accident is the lack of skid marks.
While awake, tired people show the same kinds of cognitive impairment that drunks do. They overestimate their abilities and feel they're coping just fine. They confuse keeping going with doing things properly. They operate more on automatic pilot, responding in formulaic and knee-jerk ways. The limbic system of the brain, which manages emotion, takes over from the prefrontal cortex, which manages conscious thought.
Sleepy people lose all finesse in communication, neither understanding others nor expressing themselves well. They have less self awareness or imagination, and are prone to be irritable and suspicious. They can't evaluate what they are doing, or see alternative courses of action, or foresee what an outcome is likely to be. Their attention is poor and they can't remember what they've done. They often fail to respond to, or even notice, anything unusual: think the Exxon Valdez disaster (directly attributable to a sleepy captain), or the Chernobyl nuclear meltdown.
Nor are we safe from the sleepiness of others. We will probably survive the lottery on the freeway, but we still depend on overworked doctors, politicians, bureaucrats, airline pilots, captains of industry and military men to make critical decisions on our behalf. It is not surprising that they often make a hash of it. Despite their IQs and talent, their habitual sleepiness may make them as functional as drunks.
Some people even attribute the Second World War to President Woodrow Wilson's uncharacteristic lack of judgement at the Versailles conference in 1918. Utterly exhausted from the after-effects of the Spanish flu, he allowed the French to impose crippling reparations on the defeated Germans. He just wanted to sleep! This directly contributed to the collapse of Germany's post-war democracy, and to the rise of Hitler.
Closer to home, a single night of bad sleep has an immediate effect on one's health. After bad sleep, our levels of killer T-cells drop by a quarter. These are the ones responsible for killing off infected cells, including some cancers. Levels of cortisol, which is a powerful immunosuppressant and signal of stress, rise with bad sleep. The daily rhythm of immune function, which operates in harmony with the wake/sleep cycle, is disturbed. Levels of growth hormone production, essential for repair work, drop away. (A "beauty sleep" really does do wonders for the wrinkles. Just think about the alternative: how you look after a night on the town.)
Sleep deprivation can also make us fat. A decline in growth hormone, which is only produced in deep sleep, is partly responsible for the conversion of muscle to flab as we get older. Tiredness also increases appetite, according to well mapped out hormonal pathways. I notice I often feel hungry late in the evening, when I really need to go to bed. We also become less able to produce insulin or manage our sugar levels after carbohydrate intake. Severe tiredness, in fact, mimics the first stages of diabetes.
Sleep is essential for a functional memory and a clear mind. Asleep at night, free from the daily onslaught of stimuli, the mind reviews the events of the day. It replays the dramas, discards the trivial details, extracts what is important, encodes it as coherent stories and integrates it with other key information in the brain. Like cows, we need to ruminate and digest what we've taken in! If we don't get the downtime for this essential work, our minds feel overloaded and disorganised. Sleep, dream, periods of "wakeful rest" and reverie are all necessary if we want our minds to be clear and fresh.
As if all this was not enough, poor sleep is also implicated in cardiovascular disease, anxiety and depression. So why don't we take it more seriously? People count calories in order to lose weight, but who counts the number of minutes they spend asleep each night? And if you do know, do you ever wonder if you should increase your time on the pillow?
In medical terms, poor sleep is like the elephant in the room. We may use antidepressants, blood pressure pills, sedatives to fall asleep, coffee to get us going, electronic entertainment and shopping to distract us, but we still feel tired and out-of-sorts.
The answer to all this malaise may be blazingly obvious. We feel tired (and sick and miserable and rundown) not because of some mysterious ailment. We are tired because we are tired. We are not getting enough sleep. If we slept more, we would feel a lot better.
Of course, sick people do tend to sleep, or at least lie around, more than usual. The body will force us to take it easy if we won't do so voluntarily. Unfortunately, years of sleep deprivation also lead to poor quality sleep (the many forms of insomnia), and spending more time in bed won't necessarily solve that problem.
Insomnia, stress, ill health and fatigue form a vicious feedback cycle that can be very hard to break. This stress cycle is often supported by ingrained coping behaviours (working harder and faster, recreational eating and drinking, worrying about everything just in case). This kind of stress response can work reasonably well at first, but take it to excess and watch out!
We build our habits unconsciously, but over time we gain more self understanding, and therefore more choice. If we consciously understand the high price of sleep deprivation, we can start to change it.
The trouble is we just don't value sleep. Do you know anyone who eagerly rushes to bed each night? Even when exhausted, we have a strong preference for staying awake. We love to have our brain cells tickled by something, anything, no matter how pointless. It doesn't matter if the late night TV show is dreadful. Anything can seem preferable to the nothingness of sleep. Of course, insomniacs do know the importance of sleep, but their strategies are about as effective as you would expect from people with foggy brains.
There is no secret about what contributes to good sleep. The real problem is that improving sleep is very likely to require more time than we currently give it. It would involve sacrificing some other activity from our busy day to make way for sleep. It is not surprising that we find it all too hard to contemplate.
Expensive as it seems to be, good sleep is worth the price. Do you suffer from chronic illness or pain? Are you more anxious, depressed or fat than you would like to be? Do you feel perpetually off-colour or exhausted, or prone to infections? Do you feel unable to think clearly or see things in perspective? Is the smallest thing a burden and do large matters such as the mortgage or the divorce feel incomprehensible? Are you so irritable or mentally absent that your relationships suffer? Is your memory shot, and do you feel older than you should?
Better sleep can help all of the above. If you need to heal yourself, it is worth considering this neglected medicine. I firmly believe that most of our ailments would decline in severity, or even vanish, if we just got enough sleep.