When children can get just a little more sleep each night, their school behavior and alertness levels improve, new research suggests.

"Even small changes in daily life that can allow children to add about a half hour of sleep could have a significant impact," said study author Reut Gruber, director of the attention behavior and sleep lab at the Douglas Institute at McGill University, in Quebec.

For the research, published in Pediatrics, Gruber randomly assigned about three dozen children, aged 7 to 11, to either restricted or extended sleep.

Gruber found the sleep-extension group slept on average just 27 additional minutes a night. Those in the restricted group slept, on average, 54 minutes less a night.

At the study start, both groups slept, on average, about nine hours. Children in this age group should sleep 10 or 11 hours, according to the National Sleep Foundation.

Teachers rated the children on standard measures of behavior, such as impulsivity, restlessness and emotional ability. They also noted daytime sleepiness. Those in the extra sleep group did better, showing improvement in alertness, behavior and emotions, the researchers found. Those in the restricted group had declining scores on alertness.

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Illustration: Kansas City Star/MCT