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Short sleepers and long sleepers run in families, which suggests that sleep length has a genetic basis. A multi-institutional team studied a family in which two members slept an average of 6.3 hours nightly, and the other five slept an average of 2 hours longer. The short sleepers fell asleep at about the same time as the others but awakened much earlier.
The team identified a single point mutation in a gene called DEC2; the mutation was present in the short sleepers but not in the long-sleeping family members and not in 250 other unrelated control subjects. The team then created the same mutation in transgenic mice and determined that the mutant mice were naturally active for more hours every day, slept less (with fewer hours of both REM an…