SLEEP – AN INTRODUCTION
We know that in the Paleolithic era early man slept on beds of straw, grass, brushwood and pelt. From observing the actions of chimpanzees, we know that our animal ancestors are to this day particular about their sleep. Chimpanzees build nests in trees to keep themselves safe from predators. These nests consist of a mattress lined with soft leaves and twigs. Across time and species, it seems that we don’t just need sleep, we need good-quality sleep in comfort and safety.
In this chapter I’ll try to answer some fundamental questions about sleep. What is it? What is it for? What are its features? Sometimes the answers are straightforward; often they involve the complex interplay of science, history and educated guesswork. Sleep remains something of a fascinating conundrum, but one that is essential to our existence.
How would you describe sleep? Is it a period of complete shut down? Is it total rest? Is it unconsciousness? In fact, sleep is none of these things. Although many people describe sleep as the body’s opportunity for stopping, in truth it is one of the most active periods of the day (or, rather, night) for our brain. There is no “shutting down” – two regions of the brain communicate and co-operate to create the state of sleep. In other words, sleep is an active process, not a passive one (and in the morning, the same two regions of the brain work together to create wakefulness). Some scientists think that we burn fewer than a hundred calories less during sleep than we would if we were awake but resting. This undermines the next hypothesis, that sleep is rest: sleep does involve physical rest, but we can rest nearly as effectively without actually sleeping. We aren’t unconscious during sleep, because a persistent or loud noise or other physical disturbance will wake us.
One of the most precise ways to describe sleep is to think of it as a temporary severance between the outside world and our perception or experience thereof. At the precise moment of sleep, connections between our brain and our senses virtually cease to function. During sleep we can’t really hear, taste, smell, feel touch, or see (except in our dreams). Another feature of sleep is that we can be woken from it (it is a reversible state). During dreaming sleep our limbs are immobilized in order that we can’t “act out” our dreams.
In physiological terms, sleep is a period of distinct cycles and stages. An adult with healthy sleep each night goes through four or five sleep cycles (see p.21), each demarcated by an unnoticed moment of wakefulness. Every one of those sleep cycles is itself made up of five stages of sleep – until recently thought of as drowsiness, light sleep, two periods of deep sleep and REM (or dreaming) sleep (these stages have now been reclassified; see p.21). Sleep is triggered when two particular regions of our brain communicate with one another. We’ll go into which later, but the process is rather like two conductors trying to conduct a single orchestra to play the perfect tune. When they succeed and the instruments play in harmony, we fall asleep easily. As long as no one steps out of time or tune, we stay asleep. When the instruments are out of kilter, our sleep may not be restful. When this problem persists, we say we have a sleep disorder.
WHY DO WE NEED SLEEP?
Evidence suggests that sleep is an important part of maintaining clear waking brain function. We know, for example, that people who are sleep-deprived react more slowly, and have impaired thinking skills and concentration and a poorer memory. Trying to drive when you haven’t had enough sleep is like driving under the influence of alcohol. Without sleep, moreover, we may develop poorer physical health. High blood pressure, obesity (and the health issues that go with it, such as heart disease) and stress or anxiety are all common in people who suffer from insomnia or other sleep disorders that severely impair the quality of their sleep.
However, some studies suggest that complete rest, even in a waking state, is almost as restorative to the body and mind as sleep itself. Furthermore, some muscles of the body (such as the heart and diaphragm) continue to work throughout sleep, again suggesting that sleep isn’t for resting muscles. On the other hand, we know that all living things, including plants, “go to sleep” for periods of time in the 24-hour day, and that animals with a faster metabolism (meaning that they burn energy more quickly) need more sleep than those with a slower metabolism. We know that the urge to sleep can become overwhelming (fighting sleep takes enormous effort, and eventually sleep will win), even more so when we’re ill and need to get better. Most crucially of all, evolution has not phased out sleep. So, if recuperation and restoration are not what sleep is for, and yet sleep is to all intents and purposes “involuntary”, why do we need it? Unfortunately, science is still searching for the definitive answer – if indeed there is one. For now, we have to be content simply in accepting that nature intended us to sleep, and that the better-quality sleep we can attain, the better our health and well-being and our enjoyment of our waking life.
Tiredness comes in many guises. The most common form of tiredness is the form we should all feel at the end of the waking day – a general fatigue that puts us in mind that it’s time to go to bed. This is a perfectly normal part of daily life. In itself, it may come as a feeling of mental tiredness (a long day at the office, which makes you feel sleepy) or physical tiredness (an active day hiking, cycling or gardening or doing physical work) – neither of which is a problem, as long as you feel refreshed again after a rest or ideally a good night’s sleep.
However, prolonged tiredness or tiredness that prevents you from functioning normally during the day may be a symptom of illness, or even an illness in itself. According to the Royal College of Physicians, a staggering one in ten people in the UK report feeling “tired all the time” and the problem is especially acute among women. If you feel that there’s no relief from your feelings of tiredness, you need to investigate what this might mean. Have a look at the box on pages 6–7 and see if any of the prompts apply to you – and then take appropriate action, which of course begins with making sure that your sleep is as healthy and restorative as it can be.
Austrian psychoanalyst Sigmund Freud (1856–1939) claimed that dreams were the mind’s way to release pent-up desires or forbidden thoughts. His contemporary the Swiss genius Carl Jung (1875–1961) believed they formed an expression of our “collective unconscious”. He described this as the pool of symbolic archetypes that is identical to all people in all cultures and is distinct from the “personal unconscious”, which is the mind’s mapping of our own unique experiences.
However, since Freud and Jung put forward their theories, sleep researchers have tried to explain dreaming in rather more scientific terms. Put together a simple electric circuit to light a bulb, but overload the power with too many batteries and the bulb will not light. Our minds are rather like that. During the day, the brain is bombarded with information – from our senses and our learning – for us to process and store. Overload the brain, and we might feel befuddled, exhausted or even unwell. In the 1990s sleep experts considered the possibility that our dreams crucially help the brain to make sense of the overload, sifting through and ordering all the millions of fragments of data we process every day – a sort of unravelling and filing of everything that’s on our mind so that the mind itself can work.
This certainly seems to be the case when we look at the physical evidence for dreaming. We think that dreams occur mainly during a specific phase of sleep, known as REM – or rapid eye movement – so-called because the eyes flick back and forth beneath our eyelids as we sleep. More recent research into the nature of REM has suggested that far from being a “light-hearted” break in the serious business of deep sleep, this phase must be essential to our well-being. When human beings are deprived of REM sleep, the body compensates for that deprivation by having extended periods of REM as soon as it can. If REM didn’t matter, why would the body or brain try at the soonest opportunity to catch up on the deficit? We still don’t fully understand why REM is significant, nor what dreams do exactly, but we can conclude that both seem to be an essential function of a healthy mind.
Why am I tired all the time?
In order to work out what might be causing your prolonged tiredness, you need to consider whether or not the tiredness is mental, physical, a result of your lifestyle or sleep issues, or a combination of all of these factors. Although some of the following common causes of prolonged tiredness may seem alarming – don’t panic! Think carefully about what’s going on in your life, follow the advice in this book to improve the quality of your sleep, and if your symptoms persist talk to your doctor. If neither of you can find a cause for your ongoing tiredness, it doesn’t improve and it has lasted for over six months, the tiredness is more accurately described as fatigue, and you may have chronic fatigue syndrome. Your doctor will advise you on how to manage this condition.
Mental and emotional causes
• anxiety
• depression
• bereavement
• stress, pressure or too much to do at work or at home
Physical causes
• being overweight
• being underweight
• anaemia (iron deficiency)
• diabetes
• glandular fever, or other glandular illness
• chronic illness, such as cancer or heart disease
• underactive thyroid
• muscular illness, such as multiple sclerosis
• immune conditions, including allergies and HIV
• recovery from an operation or other illness
• certain medical treatments
Lifestyle causes
• anything that disrupts the quality of your sleep, such as drinking too much alcohol or caffeine
• taking too little exercise
• taking too much exercise
• too many demands on your time – or “burning the candle at both ends”
Problems with sleep
• narcolepsy (falling asleep at the “wrong” times)
• sleep apnoea (cessation in breathing as you sleep)
• snoring
• getting too much sleep
SLEEP SCIENCE
TIREDNESS, SLEEPINESS AND FATIGUE
It’s important to spell out at this stage the differences between tiredness, sleepiness and fatigue. Tiredness is a general feeling of lethargy. Sleepiness is the feeling of having to fall asleep, an overwhelming urge to close your eyes and drift off. It doesn’t result only from tiredness, but a combination of tiredness, posture, what you’re doing at any particular time and the environment that you’re in (for example, you’re more likely to feel sleepy in a warm room than in one that’s cool). Fatigue is prolonged tiredness or excessive sleepiness and is characterized by an inability to function properly at a physical or mental level during waking hours.
The characteristics of dreams
There are innumerable ways in which we could describe our dreams, but to the scientific mind there are three main characteristics that are unique to dreaming. First, we’re in temporary paralysis during our dreams in order that we can’t act them out. Second, we rarely ever dream that we’re someone else, even if our dreams are fantastical. Finally, our dreams are fragmented, whereas life is continuous.
Then there’s the question of whether or not dreams have meaning. I think this is a matter that entirely depends upon your point of view. Since time immemorial there have been those – scientists such as Sigmund Freud among them – who have believed firmly that dreams unearth deep messages from our unconscious, helping us to make sense of past events or anxieties in our lives. I think that dreaming is a time when you become aware of how your brain is processing information. For example, teeth probably mean work to a dentist, but they may symbolize death to someone looking to interpret their dreams by traditional associations. So, do your dreams have meaning? Yes, if you believe they do.
Is there such a thing as the “right” amount of sleep? What’s normal, and what signifies that we have a problem? As with so much about sleep research, the answers are not easy to give. What’s normal, acceptable and restorative for you might for me seem excessive or too little.
Age, genetics, health, the season and the amount of racked-up sleep debt all help determine the number of hours of sleep each of us needs. And because no two of us are the same, nor are our sleep needs.
TOO MUCH AND TOO LITTLE SLEEP
The dangers of having too little sleep, and the conditions associated with too little sleep, are well-publicized, but less well known are the adverse effects and associations of too much sleep. The lists below clearly set out the effects of both. Notice that some of the effects are the same in both categories.
Effects associated with too little sleep
• Poor concentration, memory and vigilance
• Sleepiness, tiredness, fatigue, irritability, weariness
• Increased risk-taking, suggestibility
• Weight gain
• Depression
• Poor immune health
• Increased risk of diabetes and morbidity
• Increased mortality
Effects associated with too much sleep
• Obesity
• Back pain
• Headaches
• Depression
• Increased mortality
In 2009 a company in Massachusetts launched the Zeo (see box, p.228), a personalized sleep monitor that tells you how much light, deep and dreaming sleep you’ve had each night. For sleep researchers the Zeo was invaluable because it enabled us to see what an “average” night’s sleep is like over a large cross- section of the population (albeit people willing and able to buy the gadget for between $100 and $200). The readings from almost ten thousand Zeo participants told us that the average American sleeps 6.8 hours a night, with six per cent clocking up fewer than six hours of sleep a night and 12 per cent having eight hours or more.
So, does that mean that around seven hours sleep a night is what we should aim for? Perhaps. In order to provide guidelines, the expert consensus is that healthy adults should have between seven and nine hours sleep. Teenagers need one to two hours more a night; and newborns under two months old should sleep between 12 and 18 hours in every 24. The sleep needs of people aged 65 and over naturally decrease, although there is much speculation as to why, including the consideration that certain medications may disrupt sleep.
As ever, this information is relevant only in light of your uniqueness. Although seven hours might suit your partner, you might need closer to nine. In this book, I’ve assumed that you’re aiming to sleep for eight hours a night, but do adjust my advice in light of your own needs.
Sleepiness is a basic “physiological need” state. You might compare it to feeling hungry or thirsty. In a different way to hunger and thirst, though, the less good-quality sleep you have, the greater your sleepiness, not only when you’re about to go to bed, but at other times, too.
How sleepy you feel over the course of the day will depend upon all sorts of factors, including your general health, your age and what’s going on around you. If you’re stimulated and distracted, it can (up to a point) be quite easy to cast aside sleepiness and work through it. If you’re bored or doing something monotonous, sleepiness is harder to ignore. The elderly often feel sleepy between two and three o’clock in the afternoon, our “natural” siesta; while young adults, commuting from work on their way home, often report feeling sleepy as they drive.
In this respect, sleepiness is dangerous – but not only for your safety while driving a car. It can also affect your critical thinking and memory.
There are three main factors that affect daytime sleepiness:
• The duration of your nighttime sleep (how long you’ve slept during the night).
• The quality of your nighttime sleep (how well you’ve slept).
• The circadian time (the time of day).
Measuring sleepiness
In 1990, Dr Murray Johns, the founder of the Sleep Disorders Unit at Epworth Hospital in Melbourne, Australia, devised the “Epworth Sleepiness Scale” (ESS) in order to assess the daytime situations in which clients at his sleep clinic were most likely to feel an overwhelming desire to nod off. He asked his clients to score eight potentially sleep-inducing scenarios on a rising scale of zero to three – with zero indicating that the client wouldn’t feel sleepy in that situation and three indicating that the client would almost certainly nod off.
The scenarios Dr Johns gave were sitting reading; watching TV; sitting inactive in a public place; being a passenger in a car for an hour without a break; lying down to rest in the afternoon; sitting talking; sitting quietly after an alcohol-free lunch; and driving, but being stopped for a few minutes in traffic. If his patients scored nine or more, he took that to be a good indicator that they might in fact have a sleep disorder. He assessed that healthy sleepers scored around five.
Measuring fatigue
If the ESS measures general levels of sleepiness, the Fatigue Severity Scale (FSS), developed by Dr Lauren Krupp of New York State University, estimates levels of weariness. Initially created to assess fatigue in patients with multiple sclerosis and the auto immune condition lupus, the scale is now used to assess likelihood of a sleep disorder. Patients are asked to rate statements relating to how fatigued they feel in certain situations. For example, on a rising scale of one to seven for each, do you feel that fatigue interferes with your family and work time? Your sustained physical functioning? Your general functioning? And your ability to carry out your responsibilities? Similarly, is fatigue brought on by exercise? Does it affect your levels of motivation? And does it force you to shorten periods of activity? Totting up your score for each, a total of 20 or more suggests you need to take action.
There are lots of online resources that enable you to take the ESS or the FSS, or tests like them. Or, alternatively you can simply score your responses to the scenarios as I’ve given them here. Over the course of this book, I’ll show you ways in which you can considerably improve those scores, which itself means that you’ll have improved the quality of your sleep.