The Relationship Between Sleep‐Disordered Breathing Severity and Daytime Adaptive Functioning in Children with Down Syndrome

Dear Editor,

Obstructive sleep apnea (OSA) is a condition characterized by snoring and repetitive episodes of upper airway obstruction during sleep, leading to sleep disturbance and/or abnormalities in gas exchange (hypoxia/hypercapnia). Children with Down Syndrome (DS) are at an increased risk of OSA, with 24–59% affected 1, 2 compared with 1–5% in the general pediatric population 3. Obstructive sleep apnea has substantial impacts on learning, behavior, and quality of life in typically developing children 3. Children with DS would be expected to be similarly affected, with evidence to date suggesting that cognitive deficits in these children may be related to the severity of OSA 4, 5. Two studies have demonstrated impairments in cognition, particularly verbal IQ, verbal fluency, and cognitive flexibility in children with DS and OSA compared to those who do not have OSA 4, 6.

Routine screening on history followed by polysomnography (PSG) for symptomatic patients to determine the severity of OSA is recommended for children with DS by the American Academy of Pediatrics 7. However, adherence rates to this recommendation are very low 8. This may be due to the relative lack of evidence for the effects of OSA on children with DS specifically. We have previously demonstrated that children with DS referred for sleep studies have comparable symptoms to their peers for any given severity of OSA but more severe OSA on PSG 9. This suggests that they are more symptomatic by the time of referral and that there may be a relative reluctance by parents and/or doctors to investigate symptoms of OSA in these children.

We have recently undertaken a pilot study of children with DS who were having PSG for suspected OSA. Standard pediatric PSG was undertaken in an attended setting and analyzed according to the American Academy of Sleep Medicine 2012 guidelines. Severity of OSA was classified according to the frequency of obstructive events per hour of sleep (obstructive apnea–hypopnea index [OAHI]) as primary snoring (OAHI ≤ 1.0 event/h), mild OSA (OAHI 1.1–5.0 events/h), or moderate–severe OSA (OAHI > 5.0 events/h). We assessed the impact of OSA severity on adaptive functioning, a measure of how well a person handles common demands in life and how independent they are compared to others of a similar age and background, using The Adaptive Behavior Assessment System^® —Second Edition 10 Parent/Primary Caregiver Form (ABAS‐II). The form is comprised of 241 questions (0–5 years) or 232 questions (5–21 years) covering 10 skill areas: communication, community use, functional pre‐academics (0–5 years) or functional academics (5–21 years), home living, health and safety, leisure, self‐care, self‐direction, social, and motor (0–5 only) and work (5–21 years old). Skill area raw scores were converted to age‐scaled scores (population mean: 10; SD: 3), and scaled scores were combined to yield age‐corrected standard “composite” scores (population mean: 100; SD: 15) for three adaptive domains (conceptual domain: communication, functional (pre‐) academics, and self‐direction; social domain: leisure and social; practical domain: self‐care, home living, community use, and health and safety). One overall adaptive score (general adaptive composite, GAC) was also calculated using all skill area scaled scores. The ABAS manual provides normative means for children with DS.

We studied a cohort of 30 children (14 F; median age 9.1 years, IQR 4.0, 11.8), of whom five (17%) had primary snoring, 7 (23%) had mild OSA, and the remaining 18 (60%) had moderate–severe OSA, with the median obstructive apnea–hypopnea index being 6.9 events/h (IQR 2.7, 13). No significant differences were seen between the OSA severity groups for demographic or clinical factors, with the exception of an increased proportion of children with a history of cardiac disease in the OSA groups (Fisher's exact test, P = 0.02). Analysis of the ABAS showed one child whose standardized score for GAC fell in the average range (≥90). Six children (20%) had a GAC score in the below average or borderline range (71–89), and the remaining 23 children (77%) fell in the extremely low range (≤70). The distribution of GAC (mean 61.5, SD 14.6) was not different to a population of children with DS reported in the ABAS manual whose status with respect to OSA is not known (n = 21, mean 56.1, SD 14.9, T‐test P = 0.2). About 89% of children with moderate/severe OSA had a GAC score in the extremely low range, compared to 58% of those with PS or mild OSA (Fisher's exact test, P = 0.08). Differences for the GAC standardized score between OSA severity groups did not reach statistical significance (PS: 66 ± 22, mild OSA: 62 ± 17, moderate–severe OSA: 60 ± 12; one‐way ANOVA P = 0.74). The only adaptive domain on the ABAS that was significantly correlated with OAHI was the conceptual score (Spearman's rho −0.41, P = 0.02). Within that domain, there was a significant relationship only in the communication skill area (Spearman's rho −0.42, P = 0.02).

Although preliminary, in this pilot study we have found some associations between objectively assessed severity of OSA and adaptive functioning in children with DS, particularly in the area of communication skills. These findings highlight the need for better knowledge of the impact of OSA in children with DS. Given the potential impact of reduced executive functioning and verbal fluency on the execution of everyday tasks, we believe that adaptive functioning as a practical manifestation of executive functioning should be a key component of future studies. Daily living skills can dramatically affect the lives of children with DS and their families and affect their integration into the community and ability to live more independently. Our findings support the importance of taking into account comorbid disorders, specifically OSA, which may affect functioning in children with DS. Further, studies are needed to determine whether improvements in OSA seen after treatment in DS are mirrored by improvements in these key areas of daytime functioning. If so, OSA could be seen as a modifiable risk factor for poor functioning in children with DS.

Conflict of Interest

The authors declare no conflict of interest.