Adding as little as a half hour sleep can greatly improve the behavior and alertness of grade-school children, according to a study.

Parents of children with behavior problems in school may want to investigate a free and study-proven tool to improve behavior and alertness. Research published this week in the journal Pediatrics found that getting as little as a half hour more sleep makes a big difference.

And reducing sleep time can turn normally alert, well-mannered children into sleepy, poorly behaved grouches, according to the researchers, from McGill University in Quebec, Canada.

They recruited 34 typical children ages 7 to 11 who didn't have any known sleep, behavioral, medical or academic issues, then divided them into groups. One group went to bed an hour earlier than usual for a week, while the other group each went to bed an hour later than usual on weekdays. They had the teachers, who didn't know whether the child had more or less sleep, score their behavior using a well-established scale.

They found as little as 27.36 minutes of additional sleep reduced daytime sleepiness and improved behavior and emotional regulation, while loss of 54 minutes of sleep was associated with "detectable deterioration" of behavior and alertness.

“Small changes in bedtime and daily routine could go a long way,” researcher Reut Gruber, assistant professor of psychology at McGill University in Montreal, Quebec, Canada, told WebMD. “One more video game and staying a little longer in a friend's house … could add up and have a negative impact on the daytime functioning of healthy children.”

"We know that sleep deprivation can affect memory, creativity, verbal creativity and even things like judgment and motivation and being (engaged) in the classroom," Dr. Judith Owens, director of sleep medicine at Children's National Medical Center in Washington, told CNN. "When you're sleepy, (being engaged) isn't going to happen."

The American Academy of Pediatrics estimates that a third of children do not get enough sleep. The group says that children ages 3-10 need 10-12 hours of sleep each night, while those 11-12 need about 10 hours. Teenagers require about nine hours of sleep a night.

Because many parents are themselves sleep-deprived, they may not recognize the challenges it creates for children, a guide to sleep by noted. "It might be tempting to think that your kids can also get by with less sleep than they need, or that they should be able to cope fairly well with a few skipped hours here and there. However, kids who are regularly sleep deprived will exhibit some pretty difficult behaviors. They display frequent irritability, overreact emotionally, have difficulty concentrating, forget easily, wake often during the night, and may even display hyperactive behaviors."

Experts suggest that parents take control of bedtime and promote its importance by banning technology a half hour before sleep time. That includes phones, TV, computer and video games, among other things. "Take the tempo down," Dean Beebe, a professor of pediatrics at the Cincinnati Children's Hospital Medical Center and the University of Cincinnati College of Medicine, told HealthDay. Children should use that time to bathe, read a book or find different ways to relax, he suggested.

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