TV has a way of begetting more TV when you're a kid. Back in the day, I watched M*A*S*H reruns at bedtime on the small black and white tube in my room, only to then discover the fun of the Johnny Carson monologues immediately afterward. Sometimes, I made it all the way to Letterman. More TV led to more TV.

So it is no great surprise that New Zealand researchers found TV as a chief cause of later sleep routines in children. In the latest issue of Pediatrics, the researchers reported the habits of more than 2,000 children and young adults (ages 5 to 18) in the 90 minutes they had before bedtime. Common activities included homework, eating and playing video games -- but TV watching trumped them all. On average, it consumed 30 of those 90 minutes. And on average, the children who went to sleep the latest engaged in 13 more minutes of screen time.

The authors concluded that interventions to reduce TV watching at night could directly improve the amount of sleep that children and adolescents receive.