NEW YORK - Only about one quarter of children who have their tonsils and adenoids removed to relieve obstructive sleep apnea syndrome have a complete response, according to researchers.

"We should not assume that all children undergoing tonsillectomy and adenoidectomy for obstructive sleep apnea will be cured," senior investigator Dr. David Gozal told Reuters Health. "Only a small percentage will."

Obstructive sleep apnea syndrome is when person wakes up repeatedly during the night because airways become blocked for brief periods and breathing stops, also referred to as apnea. The condition can lead to daytime sleepiness and impaired concentration.

In the Journal of Pediatrics, Gozal and colleagues at the University of Louisville, Kentucky describe their study of 110 children who were evaluated using a polysomnograph, a tool to detect sleep disorders, before and after the surgery was performed.

Following surgery, only 25 percent of the children had one or no episodes of breathing interruption per hour of sleep, 46 percent had as many as four episodes per hour; and 29 percent had five or more episodes per hour of sleep.

Five or more apnea episodes per hour were significantly more common in obese children than in non-obese children (36.4 percent versus 17.6 percent), and significantly fewer obese than non-obese children had one or no episodes per hour.

Overall, 25 percent of the children had complete normalization of sleep after surgery.

Given the relatively low response rate, Gozal said, "it is important, and particularly so in more severe cases or in the presence of obesity, to repeat the sleep study after surgery to identify those children who may need additional interventions."

He suggests these might include treatment to reduce inflammation or continuous positive airway pressure, a procedure in which a face mask fitted over the nose is worn at bedtime to supply air pressure in the throat so the airways don't collapse when the patient inhales during sleep.