Good Health

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LAST MONTH a pub landlord was acquitted of drink-driving after he crashed his car while effectively 'asleep'.

Other people have stolen and even murdered while in the same state. So what makes someone sleepwalk and what can prevent it? Here, IRSHAAD EBRAHIM, medical director of the London Sleep Centre and sleep disorders consultant at St Thomas'Hospital, unravels this night-time mystery...

SLEEPWALKING, also known as somnambulism, affects around 6 per cent of children and 2 per cent of adults. Most sufferers grow out of it or simply learn to cope with it. But for some people sleepwalking can become a chronic problem.

The 100 people I treat a year might find themselves urinating in cupboards, negotiating stairs, cooking, going outside or even getting in a car and driving while they are asleep. When this occurs regularly, it not only makes people continually tired and anxious but can also affect their work, ruin relationships and put their lives at risk.

Sleepwalking is a genetic disorder. For some unknown reason it affects men more than women and the vast majority of people suffering from it have a family history of the condition. It usually occurs during the first three hours of sleep when the sleep is dreamless and deep and an episode can last from just a few minutes to an hour.

The normal sleep cycle involves distinct alternating stages from light drowsiness to deep sleep to rapid eye movement (REM) sleep, in which the eyes move rapidly and vivid dreaming is most common.

During a night, there will be several cycles of non-REM and REM sleep.

Sleepwalking most often occurs during deep non-REM sleep early in the night, just before they would slip into the REM phase of sleep.

The reason why it happens is all down to the brain. The cortex of the brain, which is responsible for consciousness, stays asleep while the area of the brain that controls our movement and sensory systems goes into awake mode.

In essence, the switch mechanism from one stage of sleep to another doesn't work and we go into what is known as a ' hyper-arousal state'. We are unable to pinpoint exactly why that is, but we know it's down to complex chemical circuits in the brain.

At this point, people tend to leave the bed and become active in a confused and disoriented state. Their eyes are open, although glazed over, and they often move slowly and clumsily. There may be incidents of sleeptalking (also known as somniloquy). The sleepwalking may even be preceded by a scream or occurrence of a 'sleep terror' (when a person awakens from a dream crying or screaming).

When occurring in a state of terror, the movements may be much more rapid, with episodes of rushing into walls, through windows and out into the street.

The person may even shout or scream.

GENERALLY, the person has absolutely no recall of the incident at all, but they may have memory of the imminent danger or specific threats against themselves, family or property.

It is a common misconception that a sleepwalker should not be woken up.

Unless that person has a history of violent or disturbed behaviour and might lash out, it is not dangerous to wake them, although it is common for the person to be confused or disoriented for a bit.

I would advise anyone dealing with a sleepwalker simply to lead them back to bed gently.

People also believe that sleepwalkers don't tend to injure themselves - but injuries caused by tripping and loss of balance are relatively common.

In the past, people suffering from this condition were often fobbed off by their GPs and told they'd 'grow out of it'. …