The hidden worlds of sleep

Millions of humans all over the planet regularly suffer a bizarre and often dangerous disorder. Blood pressure and heart rate drop dramatically, almost all of the body’s muscles become paralysed, breathing becomes shallow and irregular, thermoregulation becomes deranged so that body temperature falls, digestion grinds to a halt, and the brain endures all manner of audiovisual hallucinations. This disorder is known as “sleep”.

Although most people spend a third of their lives in this state, there is remarkably little agreement among researchers as to what the purpose of sleep really is, why it is so important to the functioning of the organism, or what the specific chemical brain processes are that lead to it. Sleep is one of the last unconquered territories of human self-knowledge. And given that sleep has an arcane but clearly intimate relationship to waking consciousness, it is also one of the great problems of brain science: the last internal frontier. The new project, one might say, is to focus some sunshine on Lethe.

For thousands of years, the black hole of sleep has been compared to death, a little rehearsal of mortality every night. For apart from general anaesthesia, only in death, sleep and coma (which can be thought of as an extreme, chronic form of sleep) is the brain switched off, do we lose knowledge of our own existence. In Greek mythology, Nyx (the god of night) has twin sons: Hypnos, god of sleep (the root of our word “hypnotism”), and Thanatos, god of death. In Shakespeare’s Hamlet, too, the hero’s most celebrated soliloquy is an extended unpacking of the metaphorical comparison (“To die – to sleep, no more”), and the method by which Claudius murders Hamlet’s father – by pouring poison into the king’s ear while he is asleep – is another pun on the theme, for the Greek Hypnos is often depicted in vase-paintings as pouring soporific liquid from a horn into the ears of the tired.

And in that sleep of death what dreams may come? Occasionally, people can “wake up” out of dreaming sleep to become conscious of their bedroom surroundings, but they are paralysed and their brains are still partly dreaming. They experience horrifying, lucid nightmares. The syndrome of sleep paralysis is probably the source for all those salacious Romantic paintings of half-dressed sleeping women on whose heaving breast sits an evil succubus, or devil, as well as for modern reports of alien abduction from the bed. And the most likely time of day for a susceptible person to suffer heart attack or stroke is at the nadir of the metabolic cycle, at about 4 or 5am – which is to say, in the very depths of sleep.

Sleep, of course, is also the time of greatest external vulnerability to surprise attack. Vigilance never sleeps – the lyrical boast of Puccini’s aria Nessun Dorma; the great soldiers of literature sleep, if they must, with their swords by their side. This is equally true for other animals: the giraffe, for instance, only takes 2.5 hours of sleep per day: being a large beast, a giraffe cannot easily hide itself under a bush to avoid marauding lions. In contrast, predators, who have little to fear, sleep a lot: the enviable domestic cat snoozes for between 16 and 20 hours per day. Yet, although there is a positive correlation across species between metabolic rate and sleep requirements, the simplistic hypothesis that sleep merely conserves energy does not explain the extraordinary complexity of sleep architecture.

***

Sleep in humans is divided into two distinct states. Dreaming occurs in REM sleep: the acronym means “rapid eye movements”, although REM is equally accompanied by bursts of middle-ear muscle activity. It is also called “paradoxical sleep”, because the brain is almost as active as when it is awake. Blood oxygen levels decrease, and carbon dioxide levels increase; some experiments have measured greater cerebral blood flow, and possibly an increase in brain protein synthesis. It is in REM that paralysis occurs, in order to prevent the acting out of the dream narrative. The diaphragm continues to inflate the lungs, but the other muscles ordinarily involved in breathing stop working, so that breathing in REM sleep becomes shallower and more disordered.

REM, however, only makes up between a fifth and a quarter of a total night’s sleep. The rest, known collectively as non-REM sleep, cycles between four different stages – the critical one is stage four, or Slow Wave Sleep, the deepest sleep of all, in which growth hormone is secreted into the bloodstream, and the brain is bathed in low-frequency, high-amplitude electricity known as delta waves. A set of all these stages, plus a stage of REM sleep, is called a sleep cycle, and one sleep cycle typically lasts about 90 minutes. The relative amounts of each stage change during the course of a night, so that there is more SWS early on, and more REM later.

Sleep has very little to do with restoration of bodily tissue: the human body can quite happily repair itself during a state of relaxed wakefulness. So sleep must be needed for the brain to switch off and recover from daytime exertions – but the relative importance of different sleep stages is still highly controversial. Dream researchers, for instance, claim that REM is the most important stage – that we go to sleep purely in order to dream, and that this stage of sleep is critical for the consolidation of memory and other cognitive functions.

Professor Jim Horne, a sleep scientist at Loughborough University, however, regards dreaming in humans merely as a kind of “cinema of the mind”, a nightly tune-up which distracts the brain from waking so that the more important business of sleep can do its work. He points out that REM deprivation in humans is fairly benign in its effects. Depressives treated with REM-inhibiting tricyclic drugs show no memory impairment, even though they do catch up on missed REM when taken off the drugs. And any cognitive deterioration could equally be attributed to the fact that REM deprivation increases libido – sexually aroused subjects perform worse on memory tasks, regardless of sleep quality – and decreases tolerance to boredom, so that people get more irritated by having to fill out “tedious” psychological questionnaires.

Horne argues that large amounts of REM in the developing brain of the human foetus act as a replacement for any external stimuli in the womb environment, and adult dreaming is little more than a hangover from this process; meanwhile, he notes laconically, memorisation is clearly optimal when you are awake. (As for the existence, much dreamed-of by cramming students the world over, of “hypnopaedia”, or sleep-learning using tapes and so on, which was explored satirically by Aldous Huxley in Brave New World and became the subject of intense interest by Soviet scientists in the 1970s – there is no evidence at all.)

Most other researchers believe that REM sleep has some cognitive purpose, even if they are not sure what. But it is generally supposed that Slow Wave Sleep is far more important for the maintenance of proper brain function. Deprive a person of SWS and mental performance becomes seriously deficient; also, increased intellectual work during the day results in greater periods of SWS, not of REM, the following night.

Professor John Shneerson at the UK’s largest sleep centre, the Papworth in Cambridgeshire, agrees: “REM is probably more to do with the development of the brain in children, getting their associations of thoughts and processes linked together.” In adult dreaming, the intellect is relatively isolated: “REM sleep seems to be associated with the more primitive part of the brain – longer established in evolutionary terms, and more associated with emotion.” The interpretation of dreams is a task best left to the hermeneutic games of the psychoanalysts.

***

Lack of sleep is torture. In Percy Shelley’s version of Prometheus Bound, the proud Titan who was chained to a rock and had an eagle pecking at his liver was encouraged in his misery by “Three thousand years of sleep-unsheltered hours”. For mortals, lack of sleep eventually kills. Why it should, even so, remains mysterious. The pioneering sleep researcher Allan Rechtschaffen was the first to demonstrate this when he devised a sadistic experiment on rats in the 1980s.

Two rats are positioned on a circular turntable above a pool of water; a wall along the diameter of the turntable divides them. One rat is hooked up to electrodes, so that whenever it tries to go to sleep the wall moves round, threatening to push the rat off the platform into the water. Rats hate getting wet, so the animal has to get up and move around again: it is completely deprived of sleep. The rat on the other side is a “control” animal to adjust for the stress of the procedure: it can sleep fine, in bursts, as long as its plucky comrade is not trying to go to sleep and setting off the revolving wall. The sleep-deprived rat dies after about 14 days. It has lost weight, even though it has been eating more: total weight loss is greater than that obtained by starving a rat to death. Yet, apart from some strange skin lesions, there appears to be nothing physically wrong with the dead rat. Large doses of antibiotics to eliminate the possibility of death by infection do not increase the rat’s lifespan.

In Jonathan Coe’s most recent novel, The House Of Sleep, the pantomime villain is a sleep researcher called Gregory Dudden, who wants to do the rat experiment on humans. For obvious ethical reasons, this is not possible in the real world. But the outcome is not in doubt anyway. For about 25 families in the world carry the gene for a terrifying disease known as Fatal Familial Insomnia. When this gene kicks in around middle age, the metaphorical wake/sleep “switch” in the brain becomes permanently jammed in the on position. The victim is simply unable to sleep regardless of any pharmaceutical or other therapy: high doses of barbiturates have no effect. The brain deteriorates rapidly, beginning to suffer hallucinations and psychosis. Speech and social interaction become impossible in this private hell, and the inevitable outcome, after about six months, is death.

***

Disordered sleep takes many forms. Narcolepsy, a condition romanticised in Gus Van Sant’s film My Own Private Idaho, is where REM sleep intrudes upon the waking brain. It is often brought on by emotional excitement: the victim suddenly loses consciousness without warning, and collapses like a puppet because of the REM-associated muscle relaxation. The obstacles that narcolepsy imposes on normal existence are clearly tremendous. John Shneerson explains that narcoleptics require detailed lifestyle counselling: “They may have difficulty crossing the road – if they get startled they might suddenly collapse in the middle of the road. Even having a bath can be dangerous, if you suddenly can’t move a muscle you could drown; and what do you do if you’re alone with children?” Happily, a new non-amphetamine stimulant drug goes a long way towards controlling the condition..

There also exists a family of parasomnias – conditions where, for whatever reason, the different brain states are not kept discrete, tend to blur into one another. Sleepwalking is usually fairly benign; less so are cases of REM Behaviour Disorder where muscle paralysis fails to occur and subjects act out their dreams physically, often hitting or trying to strangle their bed partners. At the other end of the spectrum are violent non-REM parasomnias where the sleeping person gets up and proceeds in surprisingly complex behaviours, attacking people and often exhibiting superhuman strength. One of the most intriguing recent cases was of a Toronto man called Ken Parks. One night he got up allegedly while still asleep, left the house, got into his car and drove 23km to his mother-in-law’s house, where he stabbed her to death. He then got back into his car. Halfway home he woke up and saw blood all over his hands, so he went to the nearest police station and told them, apparently in a state of extreme distress, that he thought he might have killed someone in his sleep.

Parks was acquitted of murder. Clinical tests were held to show that he exhibited all the classic signs of parasomnia. How can someone be held responsible for what they do in their sleep? A study of this and related cases proposed that such actions be classed under a new legal definition of “noninsane automatism”. That is surely a disturbing concept – having no control over your actions while being otherwise mentally healthy – although it seems that the notion of blurred brain-states is not entirely new. There is a remarkably prophetic passage in a book written in 1695 by one Thomas Tryon, A Treatise of Dreams and Visions: “Madness is nothing but an Erring Sleepifying Power, because every Madman dreameth waking.” Yet the more complex parasomnia behaviours, such as driving while ostensibly asleep, provoke scepticism in some. When I mention the Parks case to Dr Adrian J Williams of the Sleep Centre at St Thomas’ Hospital, London, he replies: “I find it difficult to understand myself.” Difficult to believe? “Yes.”

***

As the bells of Big Ben roll sonorously across the Thames on a tropical summer evening, patients at the St Thomas’ Sleep Centre are preparing for a night’s monitoring. The nerve centre of the sleep laboratory is furnished with banks of monitors, video recorders and computers. Olaf (not his real name), a baffled-looking mousy-haired man in his thirties, is being wired up to a polysomnograph, the system that will record his brain activity and other physical functions during the night.

Numerous electrodes are stuck with a foul-smelling glue onto his scalp, plus one under his bottom lip, one under his chin, and one each on the chest, abdomen and leg. Snaking from the electrodes are wires of bright blue, red, green and yellow, which all plug into a little beige jack box. It resembles a children’s electronics kit. Eventually, after more than an hour, Olaf is decorated with a nest of coloured snakes for hair, a Sellotape beard and a wire moustache. He poses for a Polaroid snapshot and scrutinises it: “I look like a monkey experiment,” he remarks glumly.

In Jonathan Coe’s novel, the sleep laboratory is a rambling stone house by the sea. In real life, a lab is like a little hotel or a classy campus residence. One woman patient tells me with relief: “I imagined sleeping in an open ward with eight fat men.” Each patient has a bedroom, with walls of plain, soothing pastel pinks, greens or blues. There is a plain wooden wardrobe and desk, plus an armchair, a washbasin and, of course, a bed. The only discordant note, reminding you that this is a surveillance arena, is struck by a video-camera lens set high on the wall opposite the bed.

Olaf, still plugged into his jack box, is led into his room by Julia, the technical officer, and wired up to yet another gadget, an oximeter. This is a tube that fits over the forefinger and shines a red light through the nail – “So you look like ET,” Julia says charmingly – in order to measure the amount of oxygen reaching the body’s extremities. Once the polysomnograph is calibrated – by telling the patient over an intercom to move his eyes, snore, point his toes, and so on – it is time for him to go to sleep.

***

Sensational stories like the Parks murder case grab the headlines with their novelty value, while the other, far more common sleep disorders, are under-recognised. Patients need to be referred by their GPs to sleep laboratories like the one at St Thomas’, but because of a lack of education about sleep, and a feeling that sleep is at the same time a private and a trivial thing, this often fails to happen. To ameliorate this situation, Neil Douglas, Professor of Respiratory and Sleep Medicine at the University of Edinburgh, and Director of the Scottish National Sleep Laboratory, is involved with the setting up of the British Sleep Foundation, which will launch in October, “to promote the public awareness of sleep and sleep disorders, particularly daytime sleepiness.”

Car crashes, for instance, are very often sleep-related. Adrian Williams notes: “If you look at road traffic accidents, a quarter of them, at least, are due to falling asleep at the wheel.” “The major problem,” Neil Douglas insists, “is that people are not aware that their sleepiness is due to an ameliorable condition, nor how dangerous driving sleepy is. They don’t realise that it’s a medical issue, and a lot of GPs graduated before the importance of sleepiness was realised.”

Some researchers go further, to claim that we are nearly all chronically sleep-deprived. Last year Dr Stanley Coren, a neuropsychologist at the University of British Columbia, published a book called The Sleep Thieves, in which he argued that since Thomas Edison invented electric light, people are sleeping on average an hour and a half less, and that for every hour of sleep you miss under a recommended total of nine, you lose five IQ points: a stupefaction which is cumulative over several days. John Shneerson agrees to the extent that harmful sleep deprivation is rife, and that it’s a social problem. “It’s a 24-hour society now,” he explains. “We have electronic entertainment, whether it’s television or videos, and also the pressure to shop all night, plus the ability to travel, and parties – so that sleep is a low priority and is being squeezed out of life. People are not really aware of the downside of restricting their sleep hours.” Neil Douglas, however, says Coren is exaggerating – “Most people get enough sleep,” he declares impatiently.

The largest single medical disorder related to sleep is sleep apnoea, which is suggested by chronic snoring and excessive tiredness in daytime. The subject periodically stops breathing, and then wakes up in order to inhale again. In extreme cases breathing can stop for up to two minutes; sufferers may only sleep for 20 seconds at a time throughout the night, never getting into restorative stage four sleep, although they have no memory of their constant nocturnal arousals. Douglas estimates that two per cent of the middle-aged population have sleep apnoea, yet don’t know it: “We reckon over 90 per cent of people with sleep apnoea in Britain have not been diagnosed, nor benefited from the therapy.”

Treatment at the moment is by CPAP machine. The acronym stands for Continuous Positive Airway Pressure – it looks like a mini vacuum cleaner and is basically an oxygen mask, attached to the head with neoprene straps, which helps air down the windpipe. It works beautifully, but ideally patients like Olaf would not have to go to bed every night looking like Hannibal Lecter: if the genetic mechanism were understood, then pharmacological treatments might be developed.

Douglas agrees: the problem is lack of money for research. “We need to make sure that adequate NHS resources are put into this condition. It’s being referred more and more, but the NHS is used to saying, ‘Well, you can have the same amount of money you had last year minus three per cent’ – and that doesn’t work if you’ve got 70 per cent new referrals per annum, as we do – 70 per cent extra every year. That’s the biggest problem that exists in the clinical practice of sleep medicine in Britain at present.”

***

I go back to the sleep lab at St Thomas’ the next morning to be shown a few polysomnograph recordings. “Shhh – sleep study in progress” read the signs in the corridor: people who work night shifts come in for monitoring during the day. For reasons of confidentiality, I am not allowed to know whether Olaf tested positive for sleep apnoea, but Julia talks me through some old cases. One cannot help but find some of the mild parasomnias entertaining. “The best one we had,” Julia says conspiratorially, “was a guy who jumped up, took the whole equipment cabinet with him and ran screaming down the corridors.”

On television programmes they always show the old, picturesque kind of EEG machine: little spidery robot arms waving across a roll of graph paper. Of course it’s really done on a computer, with a scrolling, multi-coloured hi-res display. Tweaking the mouse, Julia finds a strange case where a woman goes into stage two sleep with eye-movement bursts. She is clearly dreaming, but it isn’t REM sleep as the chin electrode shows muscle activity. “Weird!” Julia exclaims, brandishing the printout under the flickering fluorescent tubes. She yawns: she was awake most of the night. “We need daylight bulbs in this place,” she smiles, “because we’ve all got sleep disorders.”