A wake-up call for tired kids

Through various delaying tactics, games and sheer obstinacy, children often manage to push their bedtime back by an hour. But even this limited restriction on their sleep is enough to impair their brain function -- and may affect school performance.

In an Israeli study of fourth- and sixth-graders, half of a group of 77 children were asked to go to bed an hour earlier and half stayed up an hour later than their usual bedtime for three days in a row. (An hour is considered a modest manipulation of sleep time similar to what actually might happen in most households.)

Sleep monitoring revealed that most of the early-to-bed group managed to get about half an hour of extra sleep on average. The children whose sleep time was restricted got about 40 minutes less sleep than usual.

Those who stayed up an hour longer had slower reaction times and scored significantly lower on measures of learning, attention and memory than children whose sleep was extended or who had no change in their usual sleep time.

This study, published in the March/April issue of Child Development, shows that even a modest change in sleep time ultimately can affect school achievement, says lead author Avi Sadeh, professor of psychology at Tel Aviv University.

Sadeh adds that, surprisingly, children in the early-to-bed group were willing to go to sleep earlier with little incentive -- something to keep in mind when kids beg to watch just one more show or play one more video game.