Abstract
Purpose: To investigate a range of factors associated with sleep disordered breathing (SDB) in a community sample of Dunedin pre-schoolers. First, the prevalence and predictive factors associated with habitual snoring (an important indicator for SDB) were established in a community sample of 3-year olds. Second, the reliability of home-based physiological sleep measurements was determined in populations of 3-year old snorers and non-snorers. Finally, the link between SDB, cognitive development, early learning, and behavioural adjustment was investigated in 3 and 4-year olds.
Methods: First, 823 children aged 3 years 0 months to 3 years 12 months (M:F = 1:0.9) were recruited from the community. Parents completed questionnaires designed to assess information relevant to their child’s sleep. Next, a sub-sample of 170 children were recruited for further study; these children were identified as being at high (n=85 M:F=1.4:1) or low (n=85 M:F=1.4:1) risk for significant SDB from their sleep questionnaire. Each year for two years these participants completed assessments of general cognitive functioning, memory, executive functioning, early numeracy, and early literacy skills. While over the same period, children’s sleep was objectively monitored, parents completed sleep questionnaires, and parents and early childhood educators completed behavioural adjustment questionnaires.
Results: Parents reported snoring at least once a week in 36.9% of children and habitual snoring (≥4 nights per week) in 11.3% of children. Univariate analysis revealed habitual snoring was more common amongst Māori (p=0.04) and males (p=0.05), and that habitual snorers came from more socioeconomically deprived neighbourhoods (p<0.01). Multivariate analyses revealed a strong positive relationship between snoring and some health and familial factors, most notably mouth breathing, as well as parent reported child irritability (OR=2.83; 95% CI 1.4-5.6) and hyperactivity (OR=1.6; 95% CI 1.0-2.7). Children identified by their parents as likely snorers were found to snore significantly more than non-snorers (with mean rates of 25% and 7.6% respectively). Snoring (% during the night) was adequately assessed in both snoring and non-snoring children with one recording night (ICCs of 0.90 and 0.94 respectively). Other physiological measures were not as stable, with SpO2 nadir failing to reach adequate reliability in either group even after seven recording nights. Results suggest SDB accounts for moderate but statistically significant unique population variance within many measures of cognitive development, early learning, and behavioural adjustment utilised in the present research. Consistent with survey results, at age 3, some of the most consistent correlations were found between SDB and parent and early childhood educator (ECE) rated externalising behaviours. At age 4, SDB continued to be strongly correlated with parent rated externalising behaviours (r=0.494), and modestly associated with ECE ratings (r=0.174).
Conclusions: The prevalence of habitual snoring amongst New Zealand pre-schoolers is similar to that reported elsewhere, and significant ethnic disparities were found, with Māori at greater risk of SDB. Home-based sleep assessment may be a feasible alternative to polysomnography in pre-school children, as snoring can be reliably assessed with just one recording. The link between SDB and a range of cognitive, early learning, and behavioural adjustment skills was assessed, this being the first investigation of the relationship between SDB and pre-school literacy and numeracy. Results suggest significant associations between SDB symptoms and poorer performance on some cognitive, early learning, and behavioural adjustment measures, but not others. Two possible pathways linking poorer performance on specific pre-school learning domains, associated with SDB, to possible delays in reading and maths in later childhood were identified; however, further prospective longitudinal research is required to investigate these pathways. The current findings emphasize the important role of SDB in the healthy neurocognitive development of pre-school children, strengthening the call for early SDB identification and possible intervention within the pre-school population.