P127 OSA-specific hypoxic burden predicts dampened autonomic function in children with Down syndrome

Abstract Background Hypoxic burden (HB) has been associated with cardiovascular disease in adults with obstructive sleep apnoea (OSA) but has not been assessed in typically developing (TD) children with sleep disordered breathing (SDB), nor children with Down syndrome (DS) who have a higher incidence of SDB with more severe hypoxia. We assessed whether HB in TD children and children with DS was related to heart rate variability (HRV) as an indicator of poor cardiovascular outcomes. Methods Children (3-19 y, n=44) with DS and TD children matched for SDB severity, age and sex underwent overnight polysomnography and were grouped into primary snoring (PS), Mild or Moderate/Severe (MS) OSA. HRV was analysed using power spectral analysis of the electrocardiograph. Results Children with MS OSA in both groups had higher HB compared with children with PS (p<0.001 for both) and Mild OSA (p<0.01 for both). Children with DS and PS or Mild OSA had higher HB compared with TD children (PS p<0.01; Mild OSA p<0.05). There was no difference between the groups for children with MS OSA. HB significantly predicted dampened sympathetic and parasympathetic activity (low frequency power) only in children with DS; R² 0.12, β -11.31, SE 2.75, p=0.02. Conclusion HB increased with increasing OSA severity, was higher in children with DS and PS or Mild OSA, and significantly predicted dampened autonomic function in children with DS. The potential contribution of the adverse effects of HB on autonomic function adds weight to the importance of identifying and treating SDB in children with DS.