Autonomic dysfunction among overweight children with sleep-disordered breathing

<bold>Objectives:</bold> To assess the relationship between pulse rate variability (PRV) and polysomnography parameters among overweight children and adolescents. <bold>Methods:</bold> Overweight children and adolescents with snoring underwent overnight polysomnography. The PRV time series was obtained from peak-to-peak time intervals of the pulse waveforms recorded by the oximeter and used as a proxy of RR intervals. Nonlinear, time, and frequency domain analysis of PRV was performed. The percentage of successive RR intervals over 50 ms (pNN50) and the mean square root of the sum of differences between RRs (RMSSD), which reflect the vagal activity, were assessed. PRV indices correlations with Apnea Hypopnea Index (AHI), Oxygen Desaturation ≥3% Index (ODI3), and BMI z score were assessed using Spearman’s correlation. <bold>Results:</bold> Fourteen overweight children and adolescents aged 8-15 (mean age 11.9 years, 50% female) were evaluated. The mean BMI was 34.4 (SD 7.85) kg/m2, the mean z score was 2.39 (SD 0.38), and the mean HR during the sleep study was 78.4/min (SD 12.5). Mean AHI and ODI3 were 4.22/hr (±3.27) and 6.9/hr (±6.37), respectively; the majority of subjects (11/14) had obstructive sleep apnea (AHI ≥1/h. Time domain analysis showed a median value of pNN50 0.30 % and a mean value of RMSSD 18.14 ms (SD 4.26). A significant negative correlation was found between the AHI index and the pNN50 (r= -0.652, p=0.012). <bold>Conclusion:</bold> The preliminary results of our study showed a negative correlation between the severity of sleep apnoea, as indicated by the number of apnoeas during sleep, and the vagal activity, which may indicate the presence of cardiac autonomic impairment among overweight children and adolescents with SDB.