Hard to swallow........

Perhaps Shakespeare was closer to the mark than he realised when he gave Hamlet the line 'To die, to sleep, no more'. In an experiment to gain more understanding of the circadian rhythm that governs sleeping and waking, scientists bred flies missing a gene vital to the daily cycle - which made sleep deprivation have fatal consequences within hours.

Flies have a gene called 'cycle', which plays a vital role in maintaining a sleep/wake rhythm. In humans the equivalent gene is called bmal1. Scientists from the Neurosciences Institute in San Diego, California, found that flies bred lacking their cycle gene tended to die after missing only 10 hours of sleep.

However, the scientists noticed that other genes in these mutated flies were less active after sleep deprivation. These genes, which produce 'heat shock' proteins, were artificially stimulated prior to sleep deprivation, helping the flies to survive longer. As the processes involved in human sleep cycles are thought to operate on broadly the same terms, it is possible these heat shock proteins in humans may also influence recovery from the effects of sleep deprivation.

The proteins prevent cells suffering damage when exposed to stresses such as excess heat, lack of nutrition - or sleep deprivation. It could be that increased understanding of this process will lead to treatments for sleep loss.