The clock beside my bed changes to read 04.00. The flicker from the glowing digital display is barely perceptible but it is a change I have become tiresomely familiar with as I struggle to get to sleep. I have been lying awake for about an hour on this particular night after just two hours' sleep and there is no sign that I am going to drop off any time soon.
Instead, I am making a start on writing this. I have always had difficulty sleeping; even as a child I didn't particularly enjoy being in bed. At university I suffered mild bouts of insomnia and have always been a night owl. In the past nine months, however, my sleep pattern has taken an almost ruinous turn. I wake up after just an hour or two of sleep and am unable to drift off again.
During the day, I find myself unable to concentrate and feel fatigued beyond belief. I am plagued by headaches.
So I decided to find out more about my condition. With the help of Professor Kevin Morgan, from the Clinical Sleep Research Unit at Loughborough University in the UK, I became the subject of an experiment to find out what was going on when I slept.
Fitted with an actigraph, a watch-shaped device that I wore on my wrist at all times, my daily movements while awake and asleep were monitored for a week. I also completed a sleep diary, describing the quality of my sleep each night alongside the times I thought I had drifted off and woken up at. The results confirmed my fears. "You meet the diagnostic criteria for primary insomnia," said Professor Morgan. It is a condition that tends to affect younger people and is not associated with any other condition: Many people who suffer from insomnia also have diseases such as cancer, chronic pain or asthma.
Professor Morgan had even bleaker news. "Unfortunately, it tends to be a lifelong problem. It is more prevalent in people who are under pressure. Generally, people who are unhappy develop insomnia and people with insomnia are unhappy."
Insomnia is the world's most prevalent sleep disorder and affects about 10 per cent of the population. Research has also shown that insomniacs are more prone to accidents. More worryingly, however, researchers are also piecing together evidence that suggests poor sleep plays a role in a range of serious medical conditions and is even linked to early death.
Professor Francesco Cappuccio, an epidemiologist at the Warwick University, has found people who regularly sleep less than seven hours a night are at greater risk of developing high blood pressure, diabetes, heart disease and obesity than those who are well rested.
Yet, despite the apparent scale of the problem, insomnia is still relatively poorly understood.
However, a study by the University of Pennsylvania and Glasgow University is beginning to shed light on what might be going on. "People with insomnia may be asleep but their brains are more active. When you look at the microstructure of the brain patterns while they are asleep, at times their brains look more like one that is awake," said Professor Colin Espie, director of Glasgow University's Sleep Centre.
The strange blur between wakefulness and sleep combines with another factor in insomnia that is now emerging as the overriding cause of the problem — worry. Professor Espie said: "Our model sees insomnia as a disorder of selective attention that inhibits sleep. We are finding that people with insomnia are far more affected by words and pictures associated with sleep, such as beds and bedside tables, than those who have normal sleep patterns."
Those who suffer from insomnia will have some form of predisposition to the condition. Some researchers are noticing strong trends within families that are hinting at a hereditary link.
Professor Morgan believes insomnia sufferers are often found in professions that attract individuals with a certain type of mind. "They have a particular personality that puts them at risk. They tend to be people with a certain way of thinking. They are very focused and obsessional, which means they have trouble switching their brains off."
Psychologists believe worry leads to an underlying preoccupation with sleep that can prevent insomniacs from dropping off. Rather than drifting peacefully off to sleep, they fret about the prospect of not sleeping.
As for me, I still haven't managed to fall asleep. But, perhaps if I stop worrying about it, I might finally drift off.