Washington, June 1 (IANS) School kids who experience sleep-disordered breathing or daytime sleepiness are twice as likely to become bullies, according to a study.

"What this study does is raise the possibility that poor sleep, from whatever cause, can indeed play into bullying or other aggressive behaviours," says Louise O'Brien, who led the study at the University of Michigan Medical School.

University of Michigan Medical School researchers looked at school students who were bullies and found that they faced a two-fold higher risk for symptoms of sleep-disordered breathing, particularly daytime sleepiness.

"Our schools do push the importance of healthy eating and exercise," says O'Brien, assistant professor in neurology and oral and maxillofacial surgery at Michigan, the journal Sleep Medicine reports.

"But this study highlights that good sleep is just as essential to a healthy lifestyle," he adds.

O'Brien said the study showed that sleepiness seemed to be the biggest driver of behaviour problems, not the snoring -- a more obvious symptom linked with sleep-disordered breathing, an umbrella term also covering obstructive sleep apnea.

Such sleepiness could be caused by chaotic homes, fragmented sleep because of too much electronic stimulus from TV, cell phones or computers in the bedroom, says O'Brien, according to a Michigan statement.

He recommends parents remove electronic devices from bedrooms, according enough sleep a priority and encourage children to sleep well uninterruptedly.

It is recommended that children in pre-school age sleep between 11 and 13 hours a night, and those in school between 10 and 11 hours.