Improving Obstructive Sleep Apnoea Mitigates Dampened Heart Rate Responses to Respiratory Events in Children With Down Syndrome.

Children with Down syndrome (DS) have a dampened heart rate (HR) response at obstructive respiratory event termination compared with typically developing children. Whether improving obstructive sleep apnoea (OSA) severity improves the HR response to both obstructive and central events remains unknown. Twenty-four children (3-19 years at baseline) were included. Children were grouped into improved (decrease in obstructive apnoea-hypopnoea index to ≤ 50% of baseline; n = 12; seven treated between studies) and unimproved (n = 12; two treated between studies) 2 years following baseline study. Beat-to-beat HR was averaged 10 s before (pre), during, and the peak after (post) each obstructive and central event during sleep, expressed as percentage change. A total of 1018 obstructive respiratory events were analysed during total sleep; 583 events were analysed at baseline and 435 at follow-up. A total of 330 central events were analysed during total sleep; 164 central events were at baseline and 166 were at follow-up. In the unimproved group, the % change in HR from during the event to post-event was smaller at follow-up for both obstructive (mean 16.8%, 95% CI [17.4%, 20.6%] vs. 22.3% [21.1%, 26.0%] and central events: 15.8% [13.6%, 17.9%] vs. 26.1% [22.4%, 29.9%]; p < 0.05 for both). % change remained unchanged between studies in the improved group. These results suggest that the dampened HR response to respiratory events seen in children with DS worsens over time when OSA does not improve, adding weight to the need for diagnosis and management of OSA in this population.