Original ArticleSleep-disordered breathing in preschool children is associated with behavioral, but not cognitive, impairments
Introduction
Sleep-disordered breathing (SDB) is one of the most common sleep disorders in childhood. Prevalence estimates vary widely [1], but this condition may affect up to one third of children [2]. SDB is an umbrella term used to describe a collection of syndromes on a continuum of severity. Obstructive sleep apnea syndrome (OSAS) is at the most severe end of the spectrum and is characterized by snoring, apneas, and/or hypopneas associated with hypoxia, hypercarbia, or repeated arousals from sleep. Primary snoring (PS) is at the mildest end of the spectrum and is defined as habitual snoring without discrete respiratory events, gas exchange abnormalities, or evidence of sleep fragmentation [3].
There is now substantive evidence that the pediatric SDB literature is associated with daytime functional impairment including behavior problems [4], [5], cognitive deficits [6], [7], poor academic performance [8], [9], and reduced quality of life [10], [11]. The literature to date has focused primarily on school-aged children. However, SDB is most prevalent in the preschool years (3–5 years of age) [2], [12], [13], a period of particularly rapid cerebral and functional development. The presumed causative mechanisms for poor functional outcomes in SDB, hypoxic cerebral insult and sleep disturbance, may therefore be particularly important in young children as evidence suggests that the brain is uniquely vulnerable to the pathological effects of SDB during the preschool years [14], [15].
The majority of pediatric SDB is due to adenotonsillar hypertrophy and the gold standard treatment is adenotonsillectomy, which, due to the associated risk of surgery in young children, is generally only recommended for more severe cases [16]. However, a number of studies have now shown that many children with even very mild forms of SDB are at risk of poor outcomes [6], [17], [18], [19], [20], [21], [22], though this group is often untreated. Thus, accurate identification of children most likely to benefit from treatment is a clinical imperative.
To date, only two studies have focused on outcomes in preschool children with SDB diagnosed with the gold standard of polysomnography (PSG) [23], [24], and these studies have been limited by small samples and a lack of comprehensive neurobehavioral assessments. Other studies have typically relied on parent report of SDB symptoms or at-home oximetry rather than PSG [2], [4], [17], [25], [26], have not studied a representative sample [27], or have focused on children just older than the preschool age range [8], [28], [29], [30].
In light of the need for better understanding of the daytime effects of SDB in preschool children, the present study aimed to: (1) characterize cognitive and behavioral functions of preschool children referred for clinical assessment of SDB, and to compare these children with matched non-snoring control children recruited from the community; (2) determine whether outcomes vary according to SDB severity; and (3) determine whether both cognitive and behavioral measures correlate with PSG-derived indices of sleep or breathing disturbance. The hypotheses tested were that preschool children with SDB would show impaired cognition and behavior when compared to non-snoring controls, that even children with very mild SDB would show impairments across outcome domains, and that cognitive and behavioral measures would show dose-dependent relationships with indices of SDB severity.
Section snippets
Methods
The current study comprised one component of a larger project funded by the National Health and Medical Research Council of Australia examining sleep quality, cardiovascular function, and neurobehavioral outcomes in preschool children with SDB. Ethical approval was obtained through the Southern Health and Monash University Human Research Ethics Committees. Written informed consent was obtained from parents and procedures were verbally explained to children prior to commencement of the study.
Demographic, sleep, and respiratory characteristics
A total of 160 clinically referred children were recruited for the larger project. Of these children, 116 (60 PS, 32 mild OSAS, 24 MS OSAS) completed cognitive assessments, had adequate PSG data for analysis (>4 h of sleep overnight to enable clinical diagnosis), and were at least 35 weeks gestational age at birth. A total of 42 non-snoring children were recruited, of which 37 met the control group criteria. Demographics of the total sample are presented in Table 1. No significant group
Discussion
The current study investigated the daytime function of clinically-referred preschool children with SDB compared to non-snoring controls recruited from the community. We identified a pattern of significantly poorer behavioral function in children with PS and mild OSAS compared to controls, and on some measures poorer function in these groups compared to the MS OSAS group. In contrast to these findings and to our hypothesis, all SDB groups and the control group performed similarly on cognitive
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.2012.01.013.
Acknowledgements
The authors wish to thank all of the children, families, and caregivers who participated in this study, as well as the staff of the Melbourne Children’s Sleep Centre. Funding for this project was provided by the National Health and Medical Research Council of Australia Project Grant 491001 and the Victorian Government’s Operational Infrastructure Support Program.
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