Comparison of heart rate responses at respiratory event termination in children referred for assessment of hypersomnolence

BACKGROUND: Adult studies have linked disorders of hypersomnolence to impaired heart rate (HR) control. We examined HR changes during obstructive and central respiratory events in children referred for assessment of hypersomnolence compared to controls. METHODS: 20 children diagnosed with narcolepsy, 7 with idiopathic hypersomnia (IH) and 22 with subjective sleepiness who did not meet the criteria for either narcolepsy or IH were included and individually matched to 3 control groups. Multilevel modelling determined the effect of group on % HR change from a pre-event baseline to late-event and post-event periods, accounting for arousal and event length. RESULTS: There were no differences between groups for the % HR change during any of the phases analysed for either obstructive or central events. In both NREM and REM there were fewer central events associated with an arousal in the narcolepsy and narcolepsy control groups and in the subjectively sleepy group (p < 0.05). Central event duration was longer in the narcolepsy group compared to their controls during both total (p < 0.01) and NREM sleep (p < 0.001) and compared to the IH group during total sleep (p < 0.05) and NREM sleep (p < 0.01). CONCLUSIONS: Compared to controls, children with narcolepsy, IH or subjective sleepiness had similar changes in HR across respiratory events, suggesting that chronotropic dysfunction is not present in childhood. However, this may develop later in life in these conditions. Children with narcolepsy had longer central events and these were associated with fewer arousals; further research is required to determine the clinical significance of this.