Understanding Severe Sleep-Disordered Breathing in Down Syndrome: Insights from a Clinical–Polysomnographic Cohort

Introduction: Children with Down syndrome (DS) are at increased risk of sleep-disordered breathing (SDB), but clinical correlates of polysomnography-derived severity remain incompletely defined. Objectives: This retrospective clinical–polysomnographic cohort study examined associations between selected demographic, anthropometric, cardiac, and otolaryngological variables and SDB severity metrics in children and adolescents with DS. Materials and Methods: Forty-eight participants aged ≤ 18 years underwent overnight polysomnography for suspected SDB. Respiratory events were scored according to paediatric AASM criteria; hypopnoeas required a ≥30% airflow reduction associated with ≥3% oxygen desaturation and/or arousal, and ODI was calculated using ≥3% desaturation events per hour of total sleep time. Outcomes included Apnoea–Hypopnoea Index (AHI), ODI, minimum SpO2, and time with SpO2 < 90%. Results: OSA was highly prevalent: AHI ≥ 1 event/h was observed in 93.8% of participants, AHI ≥ 5 events/h in 58.3%, and AHI ≥ 10 events/h in 35.4%. Mean AHI was 10.51 ± 11.82 events/h, and mean ODI was 7.07 ± 9.31 events/h. Age at PSG was not significantly associated with AHI. AHI correlated with ODI, and clinically documented adenoidal hypertrophy correlated with both AHI and ODI. Males showed significantly higher ODI values than females, whereas sex differences in AHI, minimum SpO2, and time with SpO2 < 90% were not significant. In exploratory multivariable models, adenoidal hypertrophy was associated with higher ODI, while adenotonsillectomy was associated with lower minimum SpO2. Conclusions: The association between atrioventricular canal defect and hypoxaemic burden was not robust in bootstrap analyses. These exploratory findings do not warrant changes to current screening management strategies, but support further prospective studies incorporating standardised ENT and cardiac characterisation.