Motor Delays in Infants and Toddlers with ASD and Social Communication Delay

Background: Infants having an older sibling with an autism spectrum disorder (ASD) are at heightened risk (HR sibs) for ASD and other delays. Differences in HR sibs’ postural control, grasping, and anticipatory action responses have been reported but little is known about how these manifest in children later identified as exhibiting ASD, non-ASD social or communication delay, or no delays.

Objectives: Examine motor development between ages 6-24 months in children at heightened risk for ASD and other social communication delays, and the relation between these and developmental status between 24-36 months.

Methods: HR sibs (N=150, 95 males) and LR controls (N=60, 27 males) in this prospective, longitudinal study were assessed with the Peabody Developmental Motor Scales-2 (PDMS; Folio & Fewell, 2000) at ages 6, 10, 14, 18, and 24 months. Dependent variables were PDMS raw scores on the (1) Stationary, (2) Object Manipulation, (3) Grasping, and (4) Visual-Motor Integration subscales. Between ages 24-36 months, children were classified as No Delay (N= 134, 66 males, 79 HR, 55 LR), Social or Communication Delay (Other Delay, N= 45, 32 males, 39 HR) or ASD (N= 32, 24 males, 32 HR) using Mullen Scales of Early Learning (for No Delay and Other Delay groups), and ADOS scores and clinical judgment (for all three groups).

Results: LR and HR children in the No Delay and Other Delay groups performed similarly, so were combined for analyses to maximize sample size. Multiple one-way ANOVAs (with Bonferroni corrections) revealed significant group differences across the three groups defined by outcome classification (No Delay, Other Delay, and ASD) within each age (6, 10, 14, 18 and 24 months; e.g., Figures 1, 2). Children in the ASD group scored significantly lower on Stationary and Object Manipulation subscales than the No Delay group at 18 months and 24 months. On the Visual-Motor Integration subscale, the ASD group scored significantly lower than the No Delay group at an early age (6, 10, and 14 months). On the Grasping subscale, the ASD group scored lower than both No Delay and Other Delay groups only at age 24 months. Interestingly, the Other Delay group differed from the No Delay group on Stationary skills at 24 months and from the ASD group on Object Manipulation and Grasping subscales at 24 months.

Conclusions:

Children with ASD exhibited delay in motor development from mid-infancy into early toddlerhood. The earliest distinguishing delay was observed in visual-motor integration. This has implication for development of perception-action coupling, and could deter efficient and timely anticipatory responses and interpersonal synchrony in children with ASD. Later in the second year, toddlers with ASD exhibited slowing in fine motor development in areas integral to play development. Gross motor delays were identified in toddlers with social and communication delays at age 24 months, when more complex gross motor skills are expected to emerge. Research examining the association between these early delays and concurrent and later play and social communication in children with ASD and social communication disorders is needed.