Longitudinal Resting State Heart Rate Variability in Young Children With Autism.

As a potential indicator of social competence, the present study longitudinally examined resting state heart rate variability, measured as respiratory sinus arrythmia (RSA), at two time points in young children with autism (AU), children with intellectual disability without AU (ID), and typically developing children (TD). Participants were 29- to 81-month-old children. We replicated previous findings of lower resting state RSA in children with AU as compared to TD children. We further advanced the current knowledge by demonstrating that children with AU also exhibited lower resting state RSA compared to I children with ID. In children with AU and ID, the resting state RSA correlated with restricted, repetitive and stereotyped behavior, but the direction of the correlation was reversed between the groups. These findings indicate that lowered variability in resting state heart rate could be specific to autism in early development.