Sleep patterns often run in families, and researchers have been identifying genes that influence them, reports The New York Times.

“But while this mutated gene travels in families, its expression can vary based on what the rest of the genome looks like,” Dr. Ptacek told me. He and his colleagues concluded that “extreme morning chronotypes,” as people with advanced sleep phase are called, “are not exceedingly rare.” Their analysis showed that among visitors to a sleep clinic, some 3 in 1,000 have advanced sleep phase, and in two-thirds of those people, the pattern is familial.

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