Respiratory Sinus Arrhythmia in Children with ASD: A Biomarker for Positive Functioning

Background: Emerging neurovisceral evidence suggests that children and adolescents with autism spectrum disorders (ASD) demonstrate lowered respiratory sinus arrhythmia (RSA) at baseline compared to their typically developing peers (Bal et al., 2010; Van Hecke et al., 2009). Further, RSA patterns in ASD have been correlated to challenges in social development that characterize autistic symptomatology (Van Hecke et al., 2009). Although these recent data suggest decreased RSA in children and adolescents with ASD, which is indicative of a chronically mobilized state, hypotheses regarding autonomic variables and ASD have been articulated since the 1960s. With the improvement of data analysis and collection techniques, past hypotheses of brainstem mechanisms of ASD symptoms (MacCulloch & Williams, 1971) are being understood through current theoretical models (Porges, 2004) and data (Bal et al., 2010; Denver, 2004; Ming, Julu, Brimacombe, Connor, & Daniels, 2005). More specifically, studies indicate that hyper-arousal (i.e., decreased RSA) is associated with more ASD symptomatology, and, conversely, that higher RSA and thus vagal regulation of the heart is associated with more positive functioning in ASD.

Objectives:  The objectives of this study were to examine vagal regulation of the heart via RSA in children with ASD. We predicted that children with higher baseline RSA would demonstrate appropriate autonomic regulation to an attention-demanding task (i.e., decreased RSA to task, increased RSA at recovery), higher receptive language ability, and better social functioning. 

Methods:  Twenty-three young children (aged 4 years, 3 months to 7 years, 9 months; M = 5.72, SD = 1.17) with prior diagnoses of Autistic Disorder (n = 12), Asperger’s Disorder (n = 10), or Pervasive Developmental Disorders – Not Otherwise Specified (n = 1) participated in the study. Participants were administered the PPVT-III. Baseline heart period (HP) data were collected during a neutral 3-minute video and attention-demanding task (audiobook or music listening, 12 min) with the LifeShirt® ambulatory heart monitor. Children were administered the Social Interaction Coding Scale (SICS; Bazhenova, 2006), a semi-structured play task. HP data were edited with CardioEdit and CardioBatch (Brain-Body Center, University of Illinois at Chicago; Porges, 1985)

Results:  Higher baseline RSA amplitude was correlated with greater RSA reactivity during an attention-demanding task during task period #1 (min 1-3), r = -.60, p = .003 and to task #2 (min 10-12), r = -.69, p < .001. It was also related to greater recovery, r = -.58, p = .01. Higher baseline RSA was correlated with higher receptive language ability, r = .44, p = .04, better joint attention, r = .48, p = .03, and more conventional gestures, r = .60, p = .004.

Conclusions:  Our results suggest that RSA may function as a biomarker for more positive autonomic, cognitive, and social functioning in ASD. Due to the neural structures involved in regulating vagal influences on the heart, which are manifested in RSA, future research directions will be discussed that explore simultaneous monitoring of central nervous system activity and RSA in ASD.