Yawning Gap in Sleep Time Linked to Work, Cell Phones

Cell phones and long work hours are the biggest thieves of sleep, according to new studies in the journal Sleep. People who slept 4.5 hours or less per night worked about 1.5 hours more per weekday and nearly two hours more on weekends, researchers found. Almost two-thirds of teens who reported using their cell phones after bedtime were more tired than their peers.

A third study found that preschoolers who got less than 10 hours sleep were more hyperactive and scored worse on neurological exams. It's not clear how many of these relationships are cause and effect, however. For example, children with ADHD tend to sleep less, and only 35% of teens who considered themselves very tired attributed it to their cell phone use. (More sleep stories.)