Margaret Thatcher famously got by on four hours a night as Prime Minister, while George W. Bush wanted at least eight. The differing need for sleep extends even to those with countries to run.

Scientists may now be able to explain why: new research suggests that some of us are genetically programmed to spend longer in the Land of Nod than others.

Researchers have for the first time identified a genetic mutation linked to the amount of sleep people need.

Those who carry the mutation sleep on average two hours less a night — but still function perfectly well.

While the mutation is probably rare, it offers the strongest evidence yet of the role genes play in our need for sleep. Even if Lady Thatcher does not have this particular mutation, it is likely that aspects of her DNA allowed her to cope with so little rest.

The findings, from a team at the University of California, San Francisco, also offer insight into the biology of human sleep needs.

While a lack of sleep is generally linked to slower brain activity and poor physical and psychological health, people with the short-sleep mutation suffer none of these ill-effects and are active, vigorous and healthy. Scientists hope that by understanding the biology involved, they may eventually be able to develop drugs that help people stay awake for longer without damaging their health.

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. If we can understand this biological pathway, perhaps we can come up with a therapeutic compound. Maybe we can help people sleep less in a safe way.”

Scientists have long thought it likely that human sleep patterns are linked to genetics, and a tendency to sleep for longer or shorter periods often runs in families. Several genes have already been identified that affect whether people are likely to be up with the lark or a night owl.

No gene had previously been found to affect how long people sleep, though several are known from animal studies.

In the new research, published in the journal Science, Dr Fu’s team studied a family in which the mother and daughter require significantly less sleep than close relatives. The two sleep an average of six hours, 15 minutes each night, compared with eight hours, four minutes for other family members — but suffer no ill-effects.

“They are very healthy and extremely active,” said Dr Fu. “One of the carriers is over 70, and is perfectly healthy and travels all over the world.”

The team then looked at several genes previously associated with sleep patterns in mice. One, called DEC2, was found to be mutated in the two short-sleepers, but not in the rest of the immediate family.

The researchers then created genetically-modified mice carrying the same mutation.

“The mice with the mutation slept on average two and a half hours less than normal mice,” said Dr Fu.

The mutant mice remained just as active as normal mice.

Dr Fu said that although mutations in the DEC2 gene are almost certainly extremely rare, many other genetic variations are also likely to affect people’s need for sleep.

“There will be common variants that are involved,” she said.

In a commentary on the research for Science, Hyum Hor and Mehdi Tafti, of the University of Lausanne in Switzerland, said: “Sufficient sleep is necessary for optimal daytime performance and wellbeing, yet there is a large difference in how much sleep people need, ranging from less than six to more than nine hours.

“People at all points along this range exhibit no noticeable differences in health and waking performance.

“Those of us who envy short sleepers would like to reduce sleep duration to the minimum necessary for normal functioning, but do we know what the minimum is?

“Short sleepers are found in families, as are long sleepers, which suggests a genetic basis for sleep duration.” They said the research added new evidence by showing that a mutation in DEC2 was associated with short sleep in humans and mice.

“The question ‘how much sleep do we need?’ is not only of practical interest for obvious societal reasons, but is also of major importance for understanding sleep function.”

Sleep on it

• Salvador Dalí would doze in his chair, holding a spoon above a pan. When he fell asleep, the spoon would drop and the clatter would wake him. These catnaps sustained him for many years, though perhaps they may explain the hallucinogenic aspect of much of his work

• The inventor Nikola Tesla claimed to need only three hours of sleep, and often missed those if engrossed in a project. He wrote of his work: “Such emotions make a man forget food, sleep, friends, love, everything”

• The American President Calvin Coolidge would sleep eight hours at night and usually took a three-hour nap in the afternoon. Apparently, his first act after inauguration was to take a nap in the White House

• Albert Einstein slept ten hours a night, although if he were busy he would take 11. He thought dreams allowed him to think more clearly

• William Gladstone was said to be able to sleep at will. This gift was also enjoyed by Napoleon

• The French scientist Abraham de Moivre enjoyed sleeping up to 20 hours a day in his old age.

• Gordon Brown is notorious among colleagues for working late. Last month it was reported that Tessa Jowell and Peter Mandelson had been charged with the task of ensuring that he got more shuteye

Tim Glanfield

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