Half of all children undergoing adenotonsillectomy who were found to have attention-deficit hyperactivity disorder before the surgery no longer met the diagnostic criteria a year later, according to a prospective, controlled study.
The study strengthens previous observations linking sleep-disordered breathing–a major reason for adenotonsillectomy–with attention and behavior problems.
The investigators, who were led by Dr. Ronald D. Chervin of the University of Michigan in Ann Arbor, acknowledged that their study does not prove cause and effect.
In addition, they acknowledged that their study still leaves an important puzzle:
Although they found a strong link between adenotonsillectomy and neurobehavioral improvements (behavior, cognition, and sleepiness), they also found that sleep-disordered breathing at baseline and its subsequent improvement did not predict either baseline neurobehavioral morbidity or its improvement in any area aside from sleepiness (Pediatrics 2006;117:e769-e778).
The study involved 78 children between 5 and 13 years of age who were scheduled for adenotonsillectomy for any indication.
These children were compared with 27 control subjects in the same age range who were recruited from other surgical clinics.
Among the children who received adenotonsillectomy, 71 (91%) were judged to have a nocturnal upper airway obstruction.
Children were excluded from the study group if they required a polysomnogram for clinical purposes, if they had a history of treatment for sleep-disordered breathing, or if they had severe medical or neurologic conditions. Children were excluded from the control group for those reasons and also if they had a history of large tonsils, frequent throat infections, adenoidectomy, or tonsillectomy.
At baseline–generally within 1 month before scheduled surgery–all children underwent full-night polysomnography, and the next day received a battery of neurobehavioral assessments including the multiple sleep latency test of daytime sleepiness and a number of neuropsychological tests, Dr. Chervin and his associates said.
Polysomnography and neurobehavioral assessments were repeated at follow-up, approximately 1 year after surgery.
Before surgery, children scheduled to undergo adenotonsillectomy were significantly worse than the control children on several measures of sleep-disordered breathing, including minimum oxygen saturation, an index of obstructive apnea, a respiratory disturbance index, and the apnea-hypopnea index (AHI).
For example, the average AHI of the adenotonsillectomy children was 7.3 events per hour, compared with an average AHI of 1.2 events per hour for the control children, the investigators reported.
A year later, there were no significant differences between the adenotonsillectomy children and the control children on any polysomnographic measure. The average AHI of the control children remained 1.2 events per hour, while that of the adenotonsillectomy children declined to 1.1 per hour.
A total of 22 (28%) of the adenotonsillectomy children had ADHD at baseline, compared with only 2 (7%) of the control children, a significant difference. Of those 22 children, 11 no longer qualified for the diagnosis a year later, and there was no significant difference between the frequencies of ADHD in the two groups.
However, there was no significant association between measures of sleep-disordered breathing and either baseline or follow-up neurobehavioral morbidity.
The lack of an association could reflect inadequate sample size, Dr. Chervin and his associates said, but they noted that the sample size was more than sufficient to identify statistically significant postoperative changes in several other variables.
Another possibility is that standard measures of sleep-disordered breathing may not adequately assess the mild form of this condition that is common among children referred to adenotonsillectomy.
There is also the possibility that some correlate of sleep-disordered breathing, rather than sleep-disordered breathing itself, is the true cause of the neurobehavioral morbidity, the researchers suggested.