Sleep Apnea Specific Hypoxic Burden in Children With Down Syndrome and Typically Developing Children

Hypoxic burden (HB) is a measure incorporating frequency, depth and duration of respiratory event-related desaturations. While HB is associated with cardiovascular disease in adults with obstructive sleep apnea (OSA), it has not been assessed in typically developing (TD) children with OSA, nor in children with Down syndrome (DS), who have a higher incidence of OSA with more severe hypoxia. We assessed whether HB in these children was related to heart rate variability (HRV), an indicator of cardiovascular outcomes. Children (3-19 years, n = 44) with DS and TD children matched for OSA 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. Regression analysis determined whether HB was predictive of HRV. Children with MS OSA in both groups had higher HB compared with children with PS (p < 0.001 for both) and Mild OSA (DS, p < 0.001; TD, p < 0.05). Children with DS and PS or Mild OSA had higher HB compared with TD children (PS p < 0.05; Mild OSA p < 0.001). There was no difference between the MS OSA groups. HB predicted dampened sympathetic and parasympathetic activity only in children with DS (R ² = 0.12, β = -10.6, SE = 4.6, p = 0.03). HB was higher in children with DS and PS or Mild OSA compared to TD children and 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 OSA in children with DS.