A new study suggests that the amount of sleep you need may be written in your genes.
A team of researchers has found a genetic mutation that appears to allow some people to get by on less sleep than others. The team found the unusual mutation in a mother and daughter pair who appear to sleep less.
Sleep is essential to life, and not getting enough can cause problems. Studies show that sleep-deprived individuals have trouble performing everyday tasks, such as driving a car.
"Normal people need eight to eight-and-a-half hours of sleep," says Ying-Hui Fu, a neurologist at the University of California at San Francisco who led the study. By contrast, the two people with the mutation seemed to need just five or six hour's rest each night. The work appears in Thursday's issue of the journal Science.
Fu and her colleagues first came across the mother and daughter while they were conducting a large scale-study of people with different sleeping habits. The researchers initially mistook the pair for morning people, but follow-up work showed that they were actually sleeping well below the average. What's more, the two didn't appear unusually tired when they were awake. "It's not like they have sleep problems, they just don't sleep as much," Fu says.
The pair have a tiny mutation to a gene known as DEC2. The DEC2 gene is known to regulate the 24-hour body clocks of animals, including mice and humans, but this is the first time that an abnormal DEC2 gene has been seen in humans, Fu says.
To study the mutation in a more controlled way, Fu and her colleagues created a strain of mice with the same change to their genetic code. Just like the human subjects, the mice seemed to need less sleep than an average mouse. What's more, they seemed to recover more quickly from periods of sleep deprivation.
"This study really shows that the amount of sleep that we need each night is genetically hardwired," says Charles Czeisler, a professor of sleep medicine at the Harvard Medical School in Cambridge, Mass. But, he adds, there are still many questions to be answered about how genes like DEC2 influence sleep. In humans, for example, it's still not clear whether the gene allows people to function on less sleep or just prevents them from getting the sleep they need.
Fu agrees, but she adds, "from our discovery, you can say that our genetics does have some contribution to how much we sleep."