Original ArticleCognitive and academic functions are impaired in children with all severities of sleep-disordered breathing
Introduction
Sleep disordered breathing (SDB) is a common but under-diagnosed condition in children ranging in severity from Primary Snoring (PS) with no associated hypoxia or sleep disruption, to obstructive sleep apnea syndrome (OSAS). OSAS is characterised by snoring associated with sleep fragmentation, exaggerated upper airway resistance, intermittent hypoxia, hypercarbia, apnea, and repeated arousals. The incidence of PS in children has been reported to be between 7% and 34.5% [1], [2], [3], [4] and OSAS between 0.7% and 3.0% [5], [6], [7].
In adults OSAS is associated with deficits in a number of cognitive domains, and there is now mounting evidence that children with moderate to severe SDB are at increased risk of deficits in attention and concentration [5], [8], [9], intelligence [10], [11], executive function [12], [13], [14], [15], [16], [17], [18], memory, learning and school performance [8], [19], [20], [21], [22], [23], [24], [25], [26]. The link between SDB and cognitive deficits is further strengthened by reports of improvement in function following treatment of SDB with adenotonsillectomy [27], [28], [29], [30]. It has been suggested that a combination of repeated episodes of hypoxia and sleep disruption, both features of OSAS but not PS, contribute to these cognitive impairments [31].
Previously it was thought that only the severe end of the SDB spectrum (OSAS) was of functional significance in children. More recent studies, however, have suggested that even mild SDB can have a significant effect on children’s cognition [8], [17], [32]. These studies included methodological weaknesses which may have confounded the interpretation of findings. For example, not all studies used the gold standard of polysomnography (PSG) for the assessment of SDB severity, and several included children with PS as controls rather than recruiting a healthy comparison group. As PS represents the majority of cases referred for clinical assessment, it is vital to determine the level of severity of SDB that is associated with adverse neurobehavioral effects.
The issue is of particular importance as childhood is a vulnerable period of CNS development [33], [34], [35], [36]. In support of the unique vulnerability of the child’s brain to mild and/or transient disruptions, research investigating other childhood conditions has documented subtle consequences not observed in adult populations [34], [35]. This age-specific effect is critical as the effects of SDB in childhood may not be completely reversible [12], [21], [37], [38]. Thus, the current study aimed to compare cognitive and academic function in children with varying degrees of SDB as defined by PSG with control children with no history of SDB. We predicted that children with SDB would show impaired cognitive and academic performances compared to age-matched controls and that the degree of impairment would be related to SDB severity.
Section snippets
Methods
Ethical approval for this study was obtained from the Southern Health and Monash University Human Ethics Committees. Written informed consent was obtained from parents and verbal assent from the children prior to commencement of the study. This study formed part of a larger study which also evaluated the effects of SDB on blood pressure and cardiovascular control in these children funded by the National Health and Medical Research Council of Australia.
Demographic, sleep, and respiratory characteristics (Table 1)
No significant group differences were found for age. The control group had a significantly higher mean SES (p < 0.05) than the PS and MS OSAS groups. The MS group had a significantly higher mean BMI z-score (p < 0.05) than the other three groups.
As expected, respiratory characteristics during sleep (OAHI, RDI, ArI and SpO2 nadir) differed between the MS OSAS group and the other three groups. In addition, TST was less in the MS OSAS group compared to the control group (p < 0.05), but there were no
Discussion
The current study identified several neurocognitive deficits in children with SDB compared with normal controls. These effects, however, were not related to severity of SDB. Further, respiratory characteristics, including measures of hypoxia and disruption to sleep were not significantly correlated with any cognitive or academic measures. The prediction that mild levels of SDB would be associated with deficits in neurocognitive function was supported with all severity groups showing reduced
Conclusions
Overall, results of the present study showed several cognitive and academic deficits in children with SDB, and these deficits were not significantly related to measures of hypoxia or sleep disruption. Children with PS were also found to have an increased incidence of impairment on measures of academic function relative to controls. This study provides further evidence that children with even mild forms of SDB are at risk of cognitive and academic deficits, highlighting individual vulnerability
Conflict of interest
The ICMJE Uniform Disclosure Form for Potential Conflicts of Interest associated with this article can be viewed by clicking on the following link: doi:10.1016/j.sleep.2010.11.010.
Acknowledgements
The authors wish to thank all the children and their parents who participated in this study, and Ms. Nicole Verginis and the staff of the Melbourne Children’s Sleep Centre for their invaluable technical assistance. Funding was provided from the National Health and Medical Research Council of Australia Project Grant No. 384142.
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