Heart rate variability of typically developing and autistic children and adults before, during and after sleep

Introduction: Studies suggest a sympathetic-parasympathetic disequilibrium in children with autism spectrum disorder (ASD), compared to typically developing (TD) children. The autonomic nervous system (ANS) shows profound modification with age but studies in ASD adults are lacking. The ANS is also influenced by vigilance states such as wakefulness and sleep. The aim of this study is to explore differences in ANS activity in typically developing (TD) and ASD individuals during sleep and wakefulness, as a function of age. Methods: Four groups of participants (17 adults with ASD, 16 TD adults, 13 children with ASD and 13 TD children) were recorded for two consecutive nights in a sleep laboratory. Electrocardiogram (ECG) was sampled during wakefulness (before and after sleep) and during stage N2 and REM sleep. Groups were compared on their heart rate variability parameters (LFnu, HFnu, LF/HF ratio) in each vigilance state. Results: Results show that ASD adults had lower HFnu in the morning than TD adults (p < 0.05). During REM sleep, adults had higher LF/HF ratio than children, regardless of their clinical status (p < 0.05). Conclusions: Results of this study show autonomic distinctiveness during wakefulness specifically in ASD adults, suggesting a lower parasympathetic activity in the morning. Whether this characteristic represents a developmental feature or is related to lower sleep quality remains to be clarified.