Predictors of longer-term development of expressive language in two independent longitudinal cohorts of language-delayed preschoolers with Autism Spectrum Disorder

Abstract

Background: Studies estimate that 30% of individuals with autism are minimally verbal. Understanding what factors predict longer-term expressive development in children with language delays is critical to inform identification and treatment of those at-risk for persistent language impairments. The present study examined predictors of expressive language development in language-delayed preschoolers followed through later school-age and young adulthood.

Methods: Children using single words or less on the Autism Diagnostic Observation Schedule (ADOS) at approximately 3 years old were drawn from the Early Diagnosis (EDX) and Pathways in ASD longitudinal cohorts. Age-3 predictors of Age-19 ADOS language level were identified using Classification and Regression Trees (CART) in the EDX sample. Linear mixed models examined the effects of CART-identified predictors on Vineland expressive communication (VExp) trajectories from Age-3 to Age-19. The same linear mixed models were examined in the Pathways sample, identifying predictors of VExp from ages 3 to 10.5 years.

Results: Significantly delayed fine motor skills (T-score < 20) was the strongest CART predictor of Age-19 language. In the linear mixed models, time, Age-3 fine motor skills and initiation of joint attention (IJA) predicted VExp trajectories in the EDX sample, even when controlling for Age-3 visual receptive abilities. In the Pathways sample, time and Age-3 fine motor skills were significant predictors of VExp trajectories; IJA and cognitive skills were not significant predictors.

Conclusions: Marked deficits in fine motor skills may be a salient proxy marker for identifying language-delayed children with ASD who are at risk for persistent language impairments. This finding adds to the literature demonstrating a relation between motor and language development in ASD. Investigating individual skill areas (e.g., fine motor and nonverbal problem-solving skills), rather than broader indices of developmental level (e.g., nonverbal IQ) may provide important cues to understanding longer-term language outcomes that can be targeted in early intervention.

Keywords: Autism spectrum disorder; language; longitudinal studies; motor skills.

Figure 1.. CART predicting categorical language outcomes in the language-delayed EDX sample (n=86).

Numbers in boxes/ovals indicate most recent language (V/MV); i.e., 41/45=41 children were using at least phrases by Age-19; 45 were MV at Age-19. Joint Attention is taken from the ADOS (Initiated reflects a score of 0 or 1, Did not initiate indicates a score of 2).

Figure 2.. Parent-reported expressive language skills in language-delayed children by categorical predictors.

VExp=Vineland Expressive age equivalent (months); MSEL=Mullen Scales of Early Learning; ADOS=Autism Diagnostic Observation Schedule; M-P-R= Merrill Palmer-Revised Scales of Development.