WEDNESDAY, March 5, 2003 (HealthDayNews) -- When your kids beg to stay on the computer for just one more hour before bedtime, you can now say forget it.
And researchers will back you up.
An Israeli study of fourth- and sixth-grade children has found that up to one extra hour of sleep markedly improved their performance on tests assessing attention span and memory, both of which are necessary for optimum school performance.
"If fourth-graders get an extra hour of sleep, they can function on tests as if they were two or more years older," says Avi Sadeh, a professor of psychology at Tel Aviv University.
Sadeh is lead author of the study, which appears in the March/April issue of Child Development.
Most sleep studies focus on extreme sleep deprivation among adults, Sadeh says. However, as a parent who struggles daily with bedtimes for his own children, he was interested in finding out whether lesser amounts of sleep would really have an effect on school performance.
The answer, he and his colleagues were somewhat surprised to learn, was "yes."
"As parents, we intuitively knew there must be an effect, but as scientists with all the familiarity with previous studies, we weren't really sure we were going to find these results," he says.
"One of the effects of sleep deprivation is that if there is a sleep reduction, the sleep quality actually increases, with decreasing night awakenings and an increased percentage of sleep," he says. "So, the question was that if sleep quality improves as a compensation mechanism for sleep deprivation, will we find any important change in performance?"
"So it was very striking to find a significant effect on cognitive functioning," Sadeh says.
For the study, Sadeh studied the effects of adding or subtracting one hour of sleep time on 77 children -- 39 boys and 38 girls. Half of the children were in fourth grade, and the remainder were in sixth grade.
For the first two nights of the five-night study, the children adhered to their normal sleep pattern, which was an average of nine hours a night. For the last three nights, the children were asked to extend or reduce their sleep time by one hour. They slept with wrist monitors to record when they went to sleep and woke up, and how many times they awoke during the night.
At the beginning and end of the study, the children were given six neurobehavioral tests on a computer to measure their response times, their memory and their attention span.
One test, for instance, assessed their visual memory and visual motor-speed by showing at the top of the computer screen nine symbols paired with nine digits and asking the children to press the corresponding digits on the keyboard to mimic the order of the symbols. The scientists recorded how long it took each child to do this.
On the follow-up performance tests, those children who had the extra sleep showed significantly improved memory function and attention spans, while those who had lost sleep showed no improvement.
A child in fourth grade who got the extra sleep improved his or her performance to a fifth- or sixth-grade level; the opposite was true for the sleep-restricted group, Sadeh says.
In the test measuring timed reactions, the sleep-enhanced group showed no change in their reactions while the sleep-deprived group had significantly poorer reaction times, Sadeh says.
"This study emphasizes the importance of sleep, and how it can complement other functions," Sadeh says.
Dr. Carl E. Hunt, director the U.S. National Center on Sleep Disorders Research, agrees.
"These results are fully consistent with the few prior studies in children and with the data in adolescents and adults," he says. "The important message is that in children this age, a modest level of sleep restriction has a measurable adverse effect on alertness and on performance."
More information
The National Sleep Foundation has an interesting study about the link between children's sleep deprivation and increased risk of injury. The National Heart, Lung, and Blood Institute offers tips for parents to help their children get a good night's sleep.
