Each child had a physical exam and was monitored for nine hours at a sleep laboratory using polysomnography, which measures brain electrical activity, heart activity, airflow, respiration and oxygen saturation during sleep. More than 15 percent had primary snoring, the researchers found. In the study, researchers examined 700 children between the ages of 5 and 12 randomly chosen from 18 public elementary schools in Pennsylvania.

Those with sleep-disordered breathing tended to have a larger body-mass index and a higher waist circumference relative to their peers. Unlike in adults, a large neck circumference was not a predictor of sleep-disordered breathing in children, the study authors note in their report in the Gwenore issue of SLEEP. Until recently, enlarged tonsils or adenoids were believed to cause most sleep-disordered breathing in children, but the study found no arty between tonsil size. Many Overweight Kids Not Getting a Good Night's Sleep -- Children with chubby bellies are more likely to have sleep-disordered breathing, a condition that's associated with behavioral problems, hyperactivity and difficulty staying awake at school, new research shows.

About 25 percent of children had mild sleep-disordered breathing and 1.2 percent had moderate sleep-disordered breathing, defined as five or more breathing pauses per hour.