The amount of sleep needed each night may depend less on fluffy pillows than a single genetic mutation, according to research published.

A team of scientists claim they have identified a gene that regulates the optimum amount of human sleep each individual needs, explaining why after six hours of slumber one person may awake reborn, while another is like the living dead.

The study, published in the journal Science, identified a mother and daughter pair who needed well below the eight-and-a-half hours a night that doctors say is a must for long-term well being.

Blood tests from the easily-rested pair showed a mutation in their DEC2 gene, which has previously been implicated in the control of circadian rhythms -- the cycles that regulate the daily patterns of human behaviour.

Lead scientist Ying Hui Fu, a professor of neurology at the University of California, said her team then tested their findings on genetically modified mice and fruit flies.

The animals were observed scampering around in the dark more and sleeping less.

Lu said the observations "could provide an explanation for why human subjects with the mutation are able to live unaffected by short amounts of sleep throughout their lives."

But it is still unclear whether the mutation affects sleep quantity alone or also wakefulness. – (Sapa, August 2009)

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