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The Association between Sensory Behaviors and Heart Activity in Preschool Children with Autism Spectrum Disorder and Fragile X Syndrome
Fragile X syndrome (FXS), the most common heritable genetic cause of autism spectrum disorder (ASD), is characterized by abnormal social behavior and intellectual disability (ID). Children with FXS or ASD are at risk for physiological dysregulation, atypical sensory processing, and anxiety (Sinclair, et al, 2017). Sensory processing difficulties are linked to anxiety in ASD (Green & Ben-Sasson, 2010; Lane, et al, 2012). Further, children with FXS or ASD often show autonomic dysregulation, resulting in lower respiratory sinus arrhythmia (RSA), which may contribute to increased vulnerability to anxiety (Klusek et al, 2015; Roberts et al, 2012). Dysregulated startle response to an auditory stimulus is one example of atypical sensory processing (Kohl et al, 2014; Friedman, 2007). Understanding the influence of sensory processing on physiological regulation can provide insight into early risks and features of anxiety in these children.
Objectives: The purposes of this study are to employ a multi-method approach to (1) compare parent-reported sensory behaviors in FXS, ASD, and typically developing (TD) controls, (2) characterize and test group differences in the association between sensory processing difficulties and RSA during an anxiety-provoking task across preschoolers with FXS or ASD, and TD controls.
Methods:
Participants included 29 children with FXS, 26 TD children, and 25 children with non-syndromic ASD between the ages of 3-6 years old. The FXS and ASD groups had ID. The Sensory Experiences Questionnaire total score (SEQ) measured sensory processing. RSA was measured throughout the auditory startle task, which is comprised of the pre-startle (30 seconds), 100 dB, white-noise startle (1 second), and post-startle (30 seconds).
Results: One-way ANOVA results identified significant differences in SEQ scores across ASD, FXS, and TD children (F(2, 78) = 22.75, p < .001), with ASD highest and FXS next highest. Sensory processing and post-startle RSA were significantly correlated within the entire sample (r = -.357, p = .001). A moderated regression model showed that sensory processing predicted post-startle RSA, but only in the FXS group (b = -2.09, p < 0.01). FXS and ASD groups significantly differed on post-startle RSA, holding SEQ scores constant (b = -4.25, p = 0.02). Results also indicated a significant difference in the effect of SEQ on post-startle RSA between the FXS and ASD groups (b = 2.09, p = 0.01), in that the predicted effect of sensory difficulties on post-startle RSA is stronger for the FXS group. There was no such difference between FXS and TD groups.
Conclusions:
Consistent with prior work, these findings demonstrate greater sensory processing difficulties in both ASD and FXS groups than the TD group. A significant association between post-startle RSA and sensory behaviors was found only in the FXS group, suggesting that the more atypical sensory behaviors, the lower or more blunted RSA for the FXS group only. Further, the association between RSA and sensory processing differed between the FXS and ASD group, suggesting that these mechanisms are a unique aspect of the FXS phenotype. Future steps include evaluating the relationship between sensory processing, RSA, and anxiety symptoms.