You may have a dozy gene ... so don't lose sleep over it

Our need for eight hours' sleep or just 40 winks is down to genetic programming, according to research.

While a lack of sleep makes many people feel run down, those with a "short-sleep mutation gene" function normally during the day despite having less time in bed, the study shows.

The University of California work, published in the journal Science, studied a family in which a mother and daughter suffered no ill effects from only six hours and 15 minutes' sleep.

Those carrying the sleep mutation gene have on average two fewer hours in bed each night.

Famous short sleepers include former premier Margaret Thatcher, who got by on four hours a night, and Gordon Brown, notorious for burning the midnight oil.

Conversely, George W. Bush needed at least eight hours in bed.

Ying-Hui Fu, who led the research, said: "The majority of people need eight to eight and a half hours of sleep and though they can try to drink coffee to sleep less, it isn't their natural state."