Heart rate variability during sleep in children with autism spectrum disorder

Abstract

Purpose: Autonomic dysfunction has been reported in autism spectrum disorders (ASD). Less is known about autonomic function during sleep in ASD. The objective of this study is to provide insight into the autonomic cardiovascular control during different sleep stages in ASD. We hypothesized that patients with ASD have lower vagal and higher sympathetic modulation with elevated heart rate, as compared to typical developing children (TD).

Methods: We studied 21 children with ASD and 23 TD children during overnight polysomnography. Heart rate and spectral parameters were calculated for each vigilance stage during sleep. Data from the first four sleep cycles were used to avoid possible effects of different individual sleep lengths and sleep cycle structures. Linear regression models were applied to study the effects of age and diagnosis (ASD and TD).

Results: In both groups, HR decreased during non-REM sleep and increased during REM sleep. However, HR was significantly higher in stages N2, N3 and REM sleep in the ASD group. Children with ASD showed less high frequency (HF) modulation during N3 and REM sleep. LF/HF ratio was higher during REM. Heart rate decreases with age at the same level in ASD and in TD. We found an age effect in LF in REM different in ASD and TD.

Conclusion: Our findings suggest possible deficits in vagal influence to the heart during sleep, especially during REM sleep. Children with ASD may have higher sympathetic dominance during sleep but rather due to decreased vagal influence.

Keywords: Autism; Autonomic system; Heart rate variability; Sleep.

Fig. 1

Sleep structure (hypnogram, top) and heart rate (HR, bottom) in a child with autism spectrum disorder (ASD, left) and a typically developing child (TD, right). Hypnogram definitions: U undefined; L light, W wake; N1, N2, N3 + N4 non-REM N1, N2 and N3 + N4; REM rapid eye movement sleep

Fig. 2

Dynamic of heart rate (HR, top left panel), LF/HF ratio (top right panel), and absolute and normalized (LF, middle panels) and high (HF, bottom panels) frequency heart rate variability averaged over the first 4 sleep cycles and stages of wake (W), non-REM (N2 and N3) and REM sleep in children with ASD (red, mean and standard error, n = 20) and TD (blue, mean and standard error, n = 23)

Fig. 3

Individual heart rates (HR, top panels), and high frequency heart rate variability ((HF, bottom panels) during wake (W) and REM sleep in children with ASD (red) and TD (blue). Median and quartiles (black horizontal lines)