London: Margaret Thatcher was renowned for surviving on just four hours of sleep a night, and now scientists may have found the source of her extraordinary ability.
Researchers have discovered that a gene variant allows some people to function normally on far less than the recommended minimum amount of sleep.
American scientists at the Centre for Applied Genomics in Philadelphia discovered that people carrying the particular gene variant were able to function on fewer than five hours of sleep per night.
The researchers studied 100 sets of twins to find out which genetic variants were responsible for changes in sleep patterns.
The study revealed those with the variant chose to sleep for less time than those without it, and were also far better at mental tasks after being deprived of sleep for 38 hours.
One twin with the gene mutation had 40 per cent fewer lapses of performance during 38 hours without sleep and required less recovery sleep afterwards - sleeping only eight hours after the period of extended sleep deprivation compared with his twin brother, who slept for 9.5 hours.
"This study emphasises that our need for sleep is a biological requirement, not a personal preference," researcher Dr Timothy Morgenthaler said.
The study is published in the journal Sleep.