end Sleepless nights

Scientists have identified a brain chemical that plays a key role in falling asleep and staying awake.

Too little of the chemical and the brain nods off, too much and it can't get to sleep. The finding raises the prospect of better sleeping pills. The average Briton sleeps for six hours and seven minutes a night, well below the recommended eight hours.

Millions of prescriptions for sleep medication are written out each year, but the drugs don't work for everyone, can cause side-effects including grogginess and can be addictive.

A recent study found those who took sleeping tablets were around 36 per cent more likely to die at any given time than others.

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In the latest study, US researchers focused on a brain enzyme called calcium kinase, which was known to be involved in sleep. Giving rats a drug that stopped the enzyme from getting to work in the brain made the animals sleep more.

Encouragingly, the doses used were minimal, according to the study in The Journal of Neuroscience. Some experts say loss of sleep can have such a devastating effect on relationships that couples could sleep in separate beds