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This genetic mutation makes people feel rested on just 6 hours of sleep

Try to cheat your body out of a full night’s sleep and you’ll suffer the consequences … unless you happen to carry a rare genetic mutation. According to a new study, some people who function normally on just 6 hours of sleep harbor an altered version of a particular gene, the second gene so far linked to short sleep.

In 2009, researchers described a mother and daughter with a mutation in a gene called DEC2 who felt well rested after with about 6 hours of sleep per night. (Many experts recommend that adults get at least 7 hours.) DEC2 codes for a protein that helps turn off the expression of other genes, including the gene for the hormone orexin, known to regulate wakefulness.

Now, by studying another family containing naturally short sleepers, the scientists have identified another mutation, which they estimate is present in roughly four of every 100,000 people. Mice genetically engineered to have this mutation slept, on average, 1 hour less per day than controls, the researchers report online today in Neuron.

The mutation affects a gene called ADRB1, which encodes a receptor for the common neural signaling molecule noradrenaline. In a part of the mouse brainstem, cells studded with this receptor were active during wakefulness and quiet during deep (non–rapid eye movement) sleep, the researchers found. And stimulating these ADRB1-bearing brainstem neurons could immediately awaken them from deep sleep. They propose that the mutation renders these wake-promoting brainstem neurons more active, which could explain why its human carriers are content to sleep less.

If future studies reveal ways to re-create the effects of the known mutations with drugs, they could point to a treatment for sleep disorders—or even help the sleep-deprived masses get more benefit from less shuteye.