The etiquette of internet dating is familiar to a surprising number of people in their forties and fifties, but remains something of a mystery to older generations. Answering an advert to find a companion or spouse may seem extraordinary to many of them. However, a quick glance through internet dating profiles reveals that a large number of seemingly successful professional people, whose marriages or relationships have disintegrated, are hoping to put their lives together again with the help of cyberspace.

The divorce rate is soaring, but not all marriages fragment because of wicked parties in cellars. Boredom is often cited as the cause, but fortunately the majority (just) of married people are still able to appreciate security, stability, and a shared history and interests to make each other's company worthwhile.

Research also shows that the pleasure of living with someone - whether saint manqué, beautiful or handsome celebrity, intellectual genius or rogue - is likely to be undermined by such apparently innocuous characteristics as snoring, fidgeting restlessly in bed, constantly nipping off to the lavatory or to the kitchen to make a snack or boil a kettle. It is the repetitive nature of these blameless nuisances that become irritating to partners exhausted by the pressures of their work and a mortgage-dominated life. Divorce or separation seems too drastic an answer. Better to face the underlying difficulties caused by sleeplessness, better to correct them if poss-ible - but if not, to move out of the double bed and into separate bedrooms.

A rough survey of 2,480 UK adults found that one fifth of the people interviewed said that they are more tired on a Monday after a weekend than they were during the previous week. The effects of their sleeplessness, accumulated over the week, were often exacerbated at weekends by quarrels about minor disagreements made savage only because both partners were sleep-deprived. As people hope to be able to spend between a quarter and a third of their life sleeping, and mood and performance are dependent on a good night's sleep, insomnia is never a trivial problem. Lack of sleep, or poor-quality sleep, does not only produce irritability, poor judgment, tension, anxiety and depression, but may also increase the incidence of both accidental and natural death. About 30 per cent of all road accidents are attributed to driver fatigue; the proportion is higher if only motorway accidents are analysed. Research in 1983 showed that the overall mortality rate in patients who slept six hours or less was 30 per cent higher than it was in a comparable group who slept from seven to eight hours.

Professor Chris Idzikowski, director of the Edinburgh Sleep Centre, who was speaking in London last week, said that people need varying amounts of sleep, although the average amount required is about seven to eight hours. He said the early effects of a lack of sleep were subtle but, although ill-defined, were associated with lack of concentration and judgment, and mild depression. Professor James Horne, of Loughborough University, has demonstrated by research carried out a few years ago that the effect of sleep depriv-ation has an influence on risk-taking. He found that the risks that card players took were greater when sleep-deprived and that the greater the deprivation, the greater the risk. This research supports Professor Idzikowski's observation that remarkably poor judgment is likely to be displayed by someone woken in the middle of the night to be called upon to make a decision. The rudely awakened person should wait 20 minutes before committing himself or herself.

Professor Idzikowski discussed the advantages of having fast-acting, relatively side-effect-free sleeping pills, such as Sominex, now available over the counter. Patients are recommended to take this sedating antihistamine so that they can have an occasional good night's sleep. If their insomnia becomes a persistent problem, they need to contact their doctor to see if there is an underlying problem causing it.

Recently Circadin, a preparation of melatonin, has been approved for prescription on the NHS for people of 55 and older who have been suffering from insomnia for at least a month. Circadin is slowly released over six hours and thereby provides the body with melatonin throughout the hours of sleep. It is licensed only for a three-week course of treatment. These conditions seem to reveal supreme optimism by the doctor, or meanness by the Treasury. However, Professor Idzikowski said that there were in fact sound physiological reasons why a short course of melatonin may prove adequate, as it could be long enough to reset someone's natural clock.

The production of melatonin, a hormone produced by the pineal gland during the hours of darkness, lessens with age, so the circadian rhythms that regulate sleep may become disorganised. A night's sleep is helped by a dark bedroom but also by curtains that don't block out the dawn. Although the bedroom temperature is important, the setting varies from one person to another.

Every Wednesday at 1pm, Dr Stuttaford answers your health queries online. To submit your questions on this week's topic, keeping healthy on holiday, go to timesonline.co.uk/health