Cardiac Autonomic Function Predicts Pragmatic Language Features of the Broad Autism Phenotype in Mothers of Children with ASD

Background: The autonomic nervous system is a stress regulation system that supports social engagement. Despite efforts to characterize autonomic regulation and its role in the social impairments seen in autism spectrum disorder (ASD), evidence is inconsistent, likely due to the significant heterogeneity seen in the disorder (see Klusek et al., 2015, for review). The study of the broad autism phenotype (BAP), or subtle characteristics seen in unaffected family members that mark genetic liability to ASD, offers a framework from which to study core, genetically meaningful features of ASD while foregoing confounds related to the complex clinical presentation of the full disorder. This study adopted a BAP approach to examine cardiac markers of autonomic function among parents of children with ASD, in order to lend insight into the utility of autonomic indices as biomarkers for ASD risk. Autonomic dysregulation was also examined in relation to pragmatic language (i.e., social language) difficulties, which have been documented among parents of children with ASD as part of the BAP and are thought to reflect genetic susceptibility (i.e., Losh et al., 2008).

Objectives: This study had two research questions: (1) Do cardiac autonomic markers (i.e., heart rate, respiratory sinus arrhythmia) differ across mothers of children with ASD and control mothers? (2) Does cardiac autonomic regulation relate to pragmatic language features of the BAP?

Methods: Participants included 28 mothers of children with ASD and 28 control mothers of typically developing children (M age=43.5 years, SD=9.3). The groups did not differ in age, IQ, race, or education level (p’s<.204). Cardiac activity was sampled in a 3-min baseline period and mean estimates for heart rate (an index of general arousal) and respiratory sinus arrhythmia (an index of parasympathetic “rest and digest” function) were derived. Pragmatic language violations were coded from a 20-min conversational interview using a modified version of the Pragmatic Rating Scale (Losh et al., 2012). Samples were coded by two independent raters and consensus scores were used, with reliability prior to consensus at ICC(3,2)=.74. General linear models tested group differences on each of the cardiac variables. General linear models also tested each of the cardiac variables, group, and their interaction as predictors of pragmatic language.

Results: The groups did not differ on heart rate (p=.280, η²_p=.02) or respiratory sinus arrhythmia (p=.193, η²_p=.03). Reduced respiratory sinus arrhythmia was a significant predictor of increased pragmatic language violations across both groups (F[1,43]=4.14, p=.048, η²_p=.09).

Conclusions: Mothers of children with ASD did not show evidence of cardiac autonomic dysfunction, suggesting that autonomic dysregulation does not extend to the presentation of the BAP in females. This suggests that autonomic dysfunction in ASD may represent a secondary feature that is not associated with underlying genetic susceptibility. However, respiratory sinus arrhythmia tone did account for variation in pragmatic language variation across both groups, suggesting that parasympathetic function may mediate the presentation of BAP and ASD symptoms. Thus, autonomic regulation may play a role in social-communication competence relevant to both atypical and typical groups, and may represent a mechanistic target for intervention.