The sleepless gene.

Science World Report takes a bright-eyed, bushy-tailed look at the mutation that makes some people chipper, functional early risers:

The researchers turned to 100 pairs of twins for this particular study…. All of these pairs of twins were the same sex and were healthy with no chronic conditions. In all, the scientists measured nightly sleep duration at home for seven to eight nights with actigraphy. The researchers also examined the response to 38 hours of sleep deprivation and the length of recovery sleep in a lab.

While individual sleep needs varied, the researchers did find a small population of adults that routinely obtained less than six hours of sleep per night without any complaints of sleep difficulties and no obvious daytime dysfunction. What was more interesting was that the researchers found a twin with a variant of the BHLHE41 gene, called p.Tyr362His, who only needed a nightly sleep duration of about five hours. The non-carrier twin, in contrast, slept for about six hours per night.

Read more of their findings in Sleep. Not your sleep, the journal Sleep.