This prospective study of 105 children who had AT or unrelated surgical care shows that prominent baseline group differences in hyperactive behavior, attention deficit, sleepiness, and frequency of Attention-Deficit/Hyperactivity Disorder became difficult to identify one year after surgery. These improvements are remarkable because hyperactivity and inattention generally are expected to be chronic features in affected school-aged children.17
After AT, parental ratings for hyperactivity and cognitive scores for inattention declined by nearly 0.5 standard deviations; half of the children with Attention-Deficit/Hyperactivity Disorder no longer qualified for the diagnosis; and an objective measure of sleepiness improved. Surprisingly, common laboratory measures of SDB severity did not show associations with baseline neurobehavioral morbidity other than sleepiness, and one-year changes in laboratory measures generally did not predict neurobehavioral outcomes except for reduced sleepiness. Findings from this relatively comprehensive, long-term study of neurobehavioral outcomes after treatment of mild to moderate childhood SDB have several important implications for our understanding of pediatric SDB and for clinical practice.
Clear improvement in our subjects after AT provides new suggestive evidence for a cause-and-effect relationship between SDB – at least as identified in the office by otolaryngologists -- and several adverse behavioral, cognitive, and mental health outcomes. However, our non-randomized study design cannot prove cause and effect. Moreover, the poor correspondence between SDB measures and neurobehavioral outcomes, at baseline and follow-up, seems to run directly counter to expectations if SDB causes these morbidities. The one exception, for daytime sleepiness, is surprising because most pediatric sleep specialists have considered hyperactivity and inattention to be more prominent than overt sleepiness in childhood SDB.38
However, the extent of improvement in sleepiness, by only one minute on average in the Multiple Sleep Latency Test, may have limited clinical significance.
The lack of significant associations between SDB measures and either neurobehavioral morbidity or treatment outcomes could simply reflect inadequate sample size. However, to our knowledge this prospective series of children studied with detailed sleep and behavioral measures represents the largest to date. The sample size proved more than sufficient to identify statistically-robust post-operative changes in both explanatory and outcome variables. Therefore, we believe that lack of better correspondence between these variables may reflect limitations of standard SDB measures in assessment of the highly-prevalent, mild SDB that is commonly treated by otolaryngologists.
Support for this suspicion also derives from a growing number of other investigations. At least 3 cross-sectional studies found that hyperactive behavior or cognitive deficits correlated well with SDB symptoms such as snoring, but not polysomnographic measures of SDB severity.5,39,40
Esophageal pressure monitoring, to assess the excessive respiratory effort believed to disturb sleep in SDB,23,41
was not monitored in these studies and may have provided unique information on subtle SDB in children.42
However, successful use of this method in most of our subjects to refine a respiratory disturbance index did not improve the outcome-based effectiveness of diagnostic polysomnography. This was probably because the esophageal pressure monitoring did not prove to identify many discrete events beyond those already captured by sensitive, two-breath criteria now commonly used for pediatric hypopneas.
Several limitations to our study and its conclusions merit discussion. This study did not test the overall utility of polysomnography, as non-neurobehavioral outcomes were not studied, and neither were several other common reasons for pre-operative testing, such as assessment of operative risk.43
Families who refused to participate clearly outnumbered participants, as in most clinical research. Although data available to compare the two groups were largely reassuring, an influence of referral bias on baseline findings in particular cannot be excluded. The sleep and cognitive testing we used are considered objective, but parents and psychiatrists who assessed the children could not be masked to surgical status. Recruitment of control subjects for this study from non-otolaryngology clinics provided a group comparable in terms of exposure to the medical system, but not levels of baseline hyperactivity. Regression to the mean potentially could explain some of the neurobehavioral improvement in the AT group. However, recruitment and observation of children with neurobehavioral problems for one year without treatment was not a realistic option. Moreover, the excess neurobehavioral problems identified in our AT subjects did not arise from specific efforts to recruit for these traits. Data that compared participants to non-participants at baseline suggested only a limited difference in the frequency of parental concern for behavioral problems.
In conclusion, our data on subjects identified within otolarygnologists' practices help to characterize the cognitive and behavioral burden carried by many of their patients and relieved one year after AT. The findings suggest that SDB, though usually in the mild-to-moderate range, nonetheless carries risk for substantial, reversible neurobehavioral morbidity. The polysomnographic data, along with previous reports, increasingly suggest that children with “primary snoring” – in the absence of frequent apneic events, arousals, or gas exchange abnormalities – may still be at risk for significant neurobehavioral consequences. Published guidelines that recommend objective testing before AT, to distinguish SDB from primary snoring,8
may deserve reevaluation as new outcome data emerge on children with negative polysomnograms.10
Finally, the lack of better outcome-based performance of standard polysomnographic measures in mild pediatric SDB is a particular clinical concern: these are the children, rather than those with severe SDB, for whom effective objective measures could have the most impact. Our data must raise the possibility that some correlate of SDB, rather than SDB itself, causes the morbidity we studied.44
However, we also speculate that new SDB measures could be developed with better ability to predict neurobehavioral outcomes. Approaches with potential promise, for example, could involve characterization of the cyclic alternating pattern in children,45
respiratory and non-respiratory arousals,46
or subtle electroencephalographic changes that occur on a breath-to-breath basis during non-apneic sleep.16