Afraid to sit down in a warm room for more than five minutes in case your colleagues find you slumped forward with your head in your hands? What if pupils catch you napping - or an inspector sees you nod off? Not that you can remember the last time you had five minutes' break. Or the last time you didn't feel drained of energy. Every morning you seem to hit the ground crawling, and by mid-afternoon you feel like the walking dead. As for the evenings, they have been a washout since the start of term. All of which is a worry for someone of your age and supposed vitality. And the one thing you don't need is yet another anxiety to keep you awake at night. So what is to be done? Did workload get you into this state? Or is there something seriously the matter?
Too tired to tango
"All people," says Article V of the Bill of Nights, "should have the benefit of a well-rested workforce and be secure in the knowledge that those who are depended upon to perform critical functions in society... are attentive, alert and well rested." Bill of Nights? It's a stunt, of course, a clever piece of publicity dreamed up by an American pressure group, the National Sleep Foundation. But anyone who thinks that it's a joke being tired at work day after day should talk to the British teachers who said in a recent survey that they were too exhausted for sex after a day in the classroom.
Across the population, one in 10 people is believed to suffer from persistent tiredness at any given time, while severe tiredness, characterised by lack of energy, feelings of discomfort, loss of motivation and an inability to concentrate or make decisions, is one of the more common reasons why people visit their GP. And the fact that tiredness can lead to illness and illness to absence has not been lost on teachers'
unions. In the words of former National Union of Teachers' general secretary Doug McAvoy: "The rise in absence through sickness is no surprise given the continuing increase in teachers' workload and the pressures they face daily in our schools. The tiredness that comes from working more than 53 hours a week and the demands of dealing with increasingly unruly pupils are taking their toll."
All in the body?
It is estimated that a teacher copes with 1,000 interactions in an average working day. And as an inordinate number of these will be with pupils who, according to recent research, are likely to be getting less sleep than the average adult, it is a wonder that serious outbreaks of senseless violence are still relatively rare. But while long hours and unremitting stress undoubtedly contribute to feelings of tiredness, it would be foolish to rule out physical causes.
Among the most common culprits is the thyroid gland, which helps to regulate the body's metabolism and energy levels. Symptoms of an underactive thyroid include dry skin, hair loss, weight gain and constipation, while overproduction of thyroid hormones can result in anxiety, palpitations, sweating, weight loss and diarrhoea. Both over- and under-activity, however, are marked by tiredness and fatigue. And since the functioning of the thyroid is a finely tuned system that is controlled by several other organs, disorders are not uncommon. Even harder to pin down is anaemia, since this condition, marked by a reduced level of the oxygen-carrying pigment haemoglobin in the blood, can result from a number of disorders. Symptoms common to all types of anaemia, however, include lethargy, headaches and a general pallor.
Sleeping for two
A primary school teacher in York remembers the first three months of her pregnancy as a time of such exhaustion that she would occasionally curl up on the floor of her classroom and sleep through the lunch break. "It's beyond any kind of exhaustion you've ever felt. I'd get in the shower, and by the time I got out I'd see my bed and want to lie down again."
Only when she is into her second trimester, when her body will have finished making the placenta, can a pregnant woman hope for any relief from this overwhelming tiredness. Low blood pressure and blood-sugar levels are part of the problem, but chocolate and crisps are no use, say doctors; junk food saps energy levels further. So it's fruit, veg and lean meat, with as many short naps as possible.
No need to shout
The Trades Union Congress reckons that in any single year, one in five teachers has to take time off work because of voice-related problems, five times the rate of the UK workforce as a whole. Aggravating factors include dust and other air pollutants, it says, stressing that classroom temperature and humidity should be maintained at comfortable levels. But there is evidence also that improper use of the voice can cause strain, and that what might appear to be a localised condition can be the cause of tiredness early in the school day and exhaustion at the end of the week, as well as sore throats, back pain, neck stiffness and even migraine attacks.
In a 2001 paper called Fitness to Teach, the Department for Education and Skills and the Department of Health recommended that teachers who had voice disorders because of their work should receive medical assessment by an ear, nose and throat specialist, as well as speech and language therapy.
Those who have voice training appear to suffer from fewer voice problems than their peers. The Voice Care Network, a UK charity dedicated to helping people keep their voices healthy, suggests that small lifestyle changes and proper exercises, with a daily warm-up routine designed to keep the voice fit and flexible, "may provide the breakthrough you need for vocal health".
Blame it on ME
Then, of course, there is myalgic encephalomyelitis (ME) which, with other types of chronic fatigue syndrome (CFS), is now recognised as an illness.
Yet still it continues to challenge medical science. ME often follows a viral infection of the upper respiratory tract, an attack from which the sufferer fails to recover fully. Symptoms include muscle pains, tenderness, weakness, severe muscle fatigue, dizziness, nausea, numbness and tingling.
Treatments range from supervised graded exercise and cognitive therapy to being told to pull oneself together. The condition reportedly disappears over time, but it might take several years, so that even if depression were not present at the beginning, it often becomes a factor as the illness progresses.
Treating chronic fatigue with exercise might sound rather odd , but according to the Royal College of Psychiatrists (RCP), prolonged rest can actually make matters worse. "If you feel tired, you don't do as much as you normally would," says the RCP. "If you cut down the amount you do, your body becomes unfit. We know that just one week of resting in bed reduces your strength by 10 per cent. The more unfit you get, the more tired you will be when you try and do something."
The solution? Well, it's the usual routine. Start with a small amount of exercise - a 10-minute walk is better than nothing - and build up gradually. Try to keep it regular, and don't give up at the first sign of fatigue. This comes as part of a package of advice, all of which should be familiar to anyone who has ever read a cereal packet or a lifestyle magazine. Eat a healthy, balanced diet, cut down on caffeine and alcohol, get to work on any weight problems, and so on. Bear in mind, though, that when it comes to tiredness, being too thin can be as bad as being too fat.
And in the latter case, remember that crash diets will only add to the problem. In fact exclusion diets feature on the RCP's list of "What doesn't help", alongside vitamin and mineral supplements and stimulants of all kinds.
The right kind of sleep
So what does help? Number one on the list has to be sleep which, of course, means proper sleep at the proper time, rather than lying around in bed feeling sorry for yourself and dozing through daytime TV. But what is sleep? Considering that we all do it, the answer to that is surprisingly elusive. Most experts agree that its purpose is rest and recuperation.
But there is sleep and there is sleep. In 1953, the physiologists Eugene Aserinsky and Nathaniel Kleitman noticed that people's eyes began moving rapidly under their eyelids after about an hour in the Land of Nod. Not only that, but their electroencephalograph traces began to resemble those of wakefulness, and if they were roused at this time, they would report particularly vivid dreams. Sleep could now be divided into two categories: rapid eye movement (REM) sleep, and non-rapid eye movement (NREM) sleep.
Subsequent research subdivided NREM sleep into four stages, and scientists now agree that a typical night's sleep follows a complex pattern of increasing and decreasing depths. But on the question of why we do it, there is anything but agreement.
Shut down, switch off
Sleep first appeared as animals began regulating their own body temperatures, so it was probably a way of conserving energy while allowing the body to recuperate. But for species with complex brains, the process seems to have acquired extra functions. In deep sleep, the cerebral cortex shuts down. Is this when brain maintenance occurs?
Some researchers believe that it is during rapid eye movement sleep that our short-term memories are consolidated - saved to the hard drive, to use a computing analogy. Others reckon that dreams act like a screen-saver, providing stimulation when our bodies are inactive, so we can wake up immediately if our senses detect something happening around us.
Pass the matchsticks
One way to find out what sleep does for us is to see what happens when we don't do it for any length of time. First the good news. Unlike some unfortunate rats, which have keeled over and died after two weeks of mechanically enforced wakefulness, no human has ever suffered physical harm as a direct consequence of not sleeping. They may drive their cars off motorway flyovers or crash their lorries into bus queues, but that is because they have succumbed to what researchers call a "micro-sleep".
It appears that lack of sleep does not in itself cause physical damage, and a 17-year-old student who put himself through a 264-hour sleep deprivation experiment and who suffered increasing irritability, blurred vision, slurred speech, memory loss and confusion about his identity, was reported to be fully recovered after 15 hours (although how anyone could tell is still not clear). That said, the mental effects of sleep deprivation are not to be taken lightly. Torturers, interrogators and Ofsted inspectors have always known that, after a couple of hundred sleepless hours, our personalities start to disintegrate. Work at Loughborough University has shown that lack of sleep will make a doctor - and presumably a teacher as well - less able to switch courses of action in the light of new information. It has also shown that the brain of someone in their twenties who has not slept for 36 hours will have much in common with the brain of a 60-year-old who has.
So what keeps you awake?
Do you snore? Does your partner snore? This is no laughing matter. While certain medical conditions, such as hyposomnia, prevent sufferers from sleeping, an awful lot of nocturnal wakefulness is down to apnoea, obstruction of the breathing passages. This condition, which is exacerbated by excess fat, is what causes snoring and, in extreme cases, can lead to partial suffocation. The British Snoring and Sleep Apnoea Association reckons there are around 3,500,000 sufferers and suffering partners in the UK, and many of these will be missing out on the most effective antidote to tiredness: a good night's sleep.
Most of us believe that coffee and tea can keep us alert at work when lethargy seems inevitable. But doctors reckon that anyone drinking six cups of coffee or 10 cups of tea during the day will almost certainly have trouble sleeping at night. And the same goes for alcohol. For while a glass or two of what you fancy in the evening appears to guarantee a smooth slide into unconsciousness after a day at the whiteboard, there's a strong chance that it will wake you up again at 4 o'clock in the morning. At which point, all those drowned anxieties come skittering back like some sort of mental dawn chorus.
Sorted at last
Anyone who has ever had children, money worries, a demanding job, or all of the above, will know that tiredness and sleeplessness are two aspects of an increasingly vicious circle. All the recipes for a good night's sleep - regular bedtimes, a bedroom makeover, hot baths and a sensible diet - come to nothing when worry kicks in. Of course, worry in itself never achieved anything except more worry. Which is why therapists recommend putting your worries down on paper and sorting them out once and for all.
No matter how long the list, it can be divided into two sections: those things that, with a little help perhaps, you can hope to do something about (disruptive pupils or an aggravating colleague) and those things that it is beyond your power to fix (rising sea levels and the Middle East conflict).
At some point during the hours of daylight, plan in as much detail as possible about how you are going to address those issues that you can tackle, then put the hopeless cases firmly out of your mind. Keep the list up to date, using a bedside notebook where necessary. And with any luck, you will soon find that the most potent of all anxieties - namely the fear of tomorrow's tiredness - can now be safely included in the "fixable" half of your list.
* For information packs and advice on voice strain among teachers, visit the Voice Care Network UK (www.voicecare.org.uk).
* An information sheet about tiredness is available from the Royal College of Psychiatrists (www.rcpsych.ac.ukinfofactsheetstired.asp).
* The Child Brain Injury Trust has advice for teachers working with children who experience fatigue because of brain injury (www.cbituk.orgdownloadsindex.htm).
* Baby Centre UK has information about fatigue during pregnancy (www.babycentre.co.ukrefcap2911.html).
* The Sleep Research Centre at Loughborough University (www.lboro.ac.ukdepartmentshugroupssleep).
* For a list of books about sleep and mental health, visit the Books For Sleepless Nights site at www.sleephomepages.orgbooks
Did you know?
* No human has ever suffered physical harm as a direct consequence of not sleeping
* Research shows that the brain of someone in their twenties who has gone without sleep for 36 hours will have much in common with the brain of a 60-year-old who has slept
* Exercise is a cure. The Royal College of Psychiatrists says prolonged rest makes matters worse
* It also dismisses vitamins, minerals and stimulants of all kinds
* Scientists agree that a typical night's rest follows a complex pattern of increasing and decreasing depths - rapid eye movement (REM) andnon-rapid eye movement (NREM) sleep