Early Activity Level and Later ASD Symptoms and Attention Problems in Children with FXS

Background: Fragile X syndrome (FXS) is a genetic disorder resulting in physical, behavioral, and intellectual abnormalities. FXS is the leading known genetic cause of autism spectrum disorder (ASD) and is also commonly comorbid with ADHD and attention problems. Activity level, operationally defined as intensity of bodily vigor, early in development has been linked to later attention problems in typically-developing (TD) children. However, no studies have examined bodily vigor in relation to later attention problems and/or ASD symptoms in FXS.

Objectives: The aim of this study was to examine the relation between activity level in infancy and later ASD symptoms and attention problems in children with FXS, controlling for gross motor abilities.

Methods: This study included 22 children with FXS (18 male) assessed at 12 months of age (T1) (M = 12.96 months, SD = 0.49 months) and again between 4 and 6 years of age (T2) (M = 51.18 months, SD = 7.08 months). Measures included a five-minute behavioral observation of free play, the Vineland Adaptive Behavior Scales Gross Motor subscale raw score, the Child Behavior Checklist (CBCL) Attention Problems Subscale T-score, and the Autism Diagnostic Observation Schedule – Second Edition (ADOS-2) calibrated severity score. The behavioral observation of free play was coded from video for bodily vigor, a weighted composite score was computed, with higher scores indicating more time spent at higher bodily vigor. Partial correlations between bodily vigor at T1 and ASD and inattention symptoms at T2, controlling for T1 gross motor abilities, were run. Linear regression was then used to examine the relation between bodily vigor at T1 and ASD symptoms and attention problems at T2, controlling for gross motor abilities.

Results: Partial correlations between bodily vigor and the CBCL Attention Problems were non-significant T-score, r = .48, p = .072 when controlling for gross motor abilities, with a slight correlation that suggests significance may arise with a larger sample size. The correlation between bodily vigor and ADOS-2 calibrated severity score was non-significant, r = .26, p = .309. For CBCL Attention Problems T-score, the linear regression model was non-significant, F(2,17) = 2.77, p = .095, R² = .27, but suggestive of a significant correlation with a larger sample. Both bodily vigor (b = 16.15, p = .092) and gross motor abilities (b = -.58, p = .059) were non-significant predictors with a possibility of significance in a larger sample. For ADOS calibrated severity score, the model was non-significant, F(2,21) = 1.30, p = .295, R² = .12. Neither bodily vigor (b = 2.46, p = .225) nor gross motor abilities (b = -.10, p = .149) were significant predictors.

Conclusions: Taken together, these findings show that bodily vigor in infancy and gross motor abilities in infancy both may contribute to later attention problems, but not ASD symptoms. Future studies should take into account other variables of activity level and inattention in infancy in larger groups in order to identify the earliest risk factors of ADHD in FXS.