Neurobehavioural and neurocognitive testing
A qualified psychologist will conduct neurobehavioural and neurocognitive testing on each child at each assessment. The major outcome measure will be intellectual ability as determined by the Woodcock-Johnson III (WJ-III) Test of Cognitive Abilities [
30]. Measurement bias will be minimized by ensuring that the psychologists conducting the psychological assessments at follow-up are blinded to treatment group allocation. Participants will be coached to avoid disclosure.
Intellectual ability will be estimated by administering the seven core subtests of the WJ III: Verbal Comprehension, Visual-Auditory Learning, Spatial Relations, Sound Blending, Concept Formation, Visual Matching and Numbers Reversed. The composite of these subtests is the measure of IQ, termed GIA in the WJ III. Amongst candidate IQ tests, the WJ-III is unique in permitting testing over the proposed age range (i.e., 3.0–6.9y inclusive) using the same test items at different age bands. In addition to estimating general intellectual ability, the core subtests of the WJ III can be used to examine more specific cognitive skills that may be sensitive to sleep disruption. In the 3–6 y age range, specific cognitive abilities measured by the core subtests include: language development and verbal knowledge, complex thinking processes (long term retrieval of information, visual-spatial thinking, auditory processing and fluid reasoning), and more automatic thinking processes (short term memory and processing speed). Two additional WJ III subtests will be used to provide further assessment of attention and executive function: Retrieval Fluency and Picture Recognition. The WJ-III is normed on a sample of >8100 US children and is reported to have high test-retest reliability, high internal consistency, strong convergent validity and a robust factor structure [
30]. WJ-III testing time is estimated to be 30–50 min.
Behavioral parameters and fluid skills incorporated in executive function are deleteriously affected by OSA. These will be further tested using the Parent Rating Scale of the Behavioral Assessment System for Children-II (BASC-PRS) [
31] and the Behavior Rating of Executive Functioning (BRIEF-P) [
28].
The BASC-PRS contains 160 items and uses a four-choice response format. In the 3-6y age range, the BASC-PRS provides information about a range of areas of functioning including emotional and psychological functioning (e.g., anxiety, depression), behavior (e.g., aggression, activity levels), social skills and interaction, attention and activities of daily living. It is reported to possess high test-retest reliability, high internal consistency and a robust factor structure [
31]. The BRIEF-P consists of 63 items and uses a three-choice response format and provides information about executive function in everyday settings including skills such as behavioral and emotional control, planning and organization, attention and information processing. It is reported to possess high internal consistency and reliability, good convergent and discriminant validity and a robust factor structure [
28]. The PRS is estimated to take 15 min and the Brief-P 15 min for parents/caregivers to complete.
Finally, parent stress is associated with sleep and behavior difficulties in children so this will be assessed using the Parenting stress Index (PSI) [
32]. The PSI consists of 120 questions and yields a Total Stress Score, a Child Domain score, a Parent Domain score and a Life Stress score. Child characteristics are measured on 6 subscales: Distractibility, Hyperactivity, Reinforces Parent, Demandingness, Mood and Acceptability. Parent personality and situational variables are measured on 7 subscales: Competence, Isolation, Attachment, Health, Role Restriction, Depression and Relationship with Spouse. The PSI has satisfactory internal consistency, robust test-retest reliability [
32]. The PSI takes 20–30 min to complete.
The maximum testing time (including breaks) for neurobehavioural and neurocognitive testing is estimated to be 2 h, but 4 h will be allowed for each child for the full testing battery.
Polysomnography (PSG)
Each participant identified by questionnaire will undergo full overnight sleep studies using standard clinical pediatric techniques and analyses. At each acquisition point, the sleep study results will only be included if they capture a minimum of 4 h recording time and at least 2 cycles of REM sleep; if these are not obtained, a repeat PSG will be undertaken.
Total sleep time and the obstructive apnoea hypopnea index (AHI) defined as the total number of obstructive apnoeas, mixed apnoeas, and obstructive hypopneas per hour of sleep will be calculated. PSG will be scored using American Academy of Sleep Medicine (AASM) 2007 guidelines [
33], as these guidelines were current at the time of study design and its commencement.
Sleep study concordance
As sleep studies will be carried out in 3 different sleep laboratories, a maximum of two experienced sleep technologists will be solely responsible for analysis of the PSG studies in each center. Analysis criteria have been agreed upon and those involved in analyzing studies will meet regularly to evaluate studies and ensure concordance. No published data exists on multi-center trial concordance for pediatrics.
The severity of OSA is defined by the number of obstructive apnoea & hypopnea events that occur per hour of sleep time expressed as the index of events per hour (OAHI). Standard diagnostic categories for pediatric OSA will be used and are: Primary Snoring <1 event/h; mild OSA 1–5 events/h; moderate OSA 5–10 events/h; and severe OSA >10 events/h [
34]. Severe OSA experience nocturnal respiratory failure and severe desaturations, and there is clinical imperative for them to receive the beneficial effects of adenotonsillectomy [
34‐
36].
Data collection & storage
This study will generate a significant amount of data, due to the large amounts of data points per test and the 2 time points of study. The database for POSTA has been custom-designed to allow handling of this data. It is a secure centralized web-based system that allows transfer of data directly from source for many of the data points. Each study site can upload information directly into the centralized system, ensuring clean and compatible data for analysis. The direct export of PSG and neurocognitive data into this central database will minimize errors that could otherwise occur from manual data entry. Summary data can be generated and exported to relevant statistical packages according to requirements for data analysis (
http://www.postastudy.org).