Heart rate variability remains unchanged in children with sleep-disordered breathing.

Abstract

Objectives: Childhood sleep disordered breathing (SDB) has detrimental effects on cardiovascular health, evidenced by the development of hypertension, increased blood pressure (BP) variability and decreased nocturnal dipping [1-3]. Apnoeic event onset induces bradycardia followed by abrupt tachycardia at the end of the event [4]. We aimed to determine whether heart rate variability (HRV) was altered in primary school aged children with various severities of SDB compared to controls. Method(s): Sixty children (7-12years) referred for assessment of SDB and 20 age-matched controls with no history of snoring were studied. All underwent overnight polysomnography (PSG) and continuous BP measurement (Finometer-). Subjects were grouped according to their obstructive apnoea hypoponea index (OAHI); primary snorers (PS; OAHI <= 1 event h-1), mild (OAHI >=1- <= 5 events h-1) and moderate/severe (M/S; OAHI > 5 events h-1). All 30s PSG epochs containing ECG artifact, arousals or movements were removed. HRV was analysed by power spectral analysis during Wake, NREM1&2, SWS and REM, using Chart software (ADInstruments, Sydney, Australia). Statistical analyses were performed using Kruskal-Wallis one way ANOVA on Ranks and Dunn's Method post hoc analyses. Result(s): There were no significant differences between groups during any sleep stage for low frequency (LF), high frequency (HF), total power, or the LF/HF ratio. LF power during SWS was significantly lower than during NREM1&2 in the PS, Mild and M/S groups and also during REM in the M/S group. There were no significant differences in HF power between sleep stages in any group. Total power during SWS was significantly lower than during NREM1&2 for PS and Mild. In all groups, the LF/HF ratio was significantly lower during SWS than during Wake and REM; in the Control and Mild LF/HF during NREM1&2 was lower than during Wake; in the PS, Mild and M/S, LF/HF was lower during SWS than NREM1&2. Conclusion(s): We speculate that the development of hypertension, increased blood pressure variability and decreased nocturnal dipping that has been observed in children with SDB, occurs independently of the regulation of the autonomic nervous system during sleep as the strong dominance of the basic HR control in the different sleep stages leaves the autonomic nervous system regulation basically unaffected by SDB.