16341
Longitudinal Trajectories of Language Development in Infants and Toddlers with ASD
Delays in language and communication skills are common in young children who go on to develop Autism Spectrum Disorder (ASD). However, only a few studies have examined change in language skills longitudinally over early development or studied the predictive relationship between early language behaviors and later outcomes (see Charman et al., 2003; Ozonoff et al, 2010). In a cross-sectional study of 18 to 33 months olds, Luyster and colleagues (2008) found that non-verbal cognitive ability, number of gestures, and response to joint attention contributed to receptive language variance, while non-verbal cognition, gestures, and imitation accounted for variance in expressive language.
Objectives:
First, we aimed to characterize developmental trajectories of receptive and expressive language in high-risk infant siblings who go on to develop ASD, those who do not, and in typically developing controls. Second, we sought to extend the work of Luyster et al. (2008) by investigating which aspects of early cognitive skills and language best predict language skills at 24 months.
Methods:
205 infants with older siblings with ASD (HR) and 78 infants with typically developing older siblings (LR) were assessed longitudinally as part of a larger, multi-site, study of brain and behavioral development in ASD. Language was assessed at 6,12 and 24 months using the Mullen Scales of Early Learning, Vineland Adaptive Behavior Scales and at 12 and 24 months using the MacArthur Bates Communicative Development inventory (M-CDI). Receptive and expressive language composite scores were calculated using a mean of receptive or expressive language scores respectively from the Mullen, VABS and the number of words understood or produced on the M-CDI. Autism outcome was determined at 24 months using the ADOS and clinical best estimate.
Results:
Data were analyzed for 3 groups of infants: low-risk controls with no ASD diagnosis (LR-), high-risk siblings with an ASD diagnosis (HR+) and HR siblings without ASD (HR-). Longitudinal analyses of trajectories for expressive and receptive language composites were conducted using linear mixed models. Analyses revealed that groups began to diverge at 12 months, with the HR+ showing significantly slower growth than the other two groups in receptive, F(4,335) = 23.68, p<.01, and expressive, F(4,339) =10.09, p<.01, language. The contribution of late and early gestures from the M-CDI, motor skills, and visual reception from the Mullen at 12 months to language performance at 24 months was examined using multiple regressions. For both expressive and receptive language outcomes, the number of gestures produced at 12 months had the greatest contribution to variance at 24 months, after controlling for socioeconomic status irrespective of group.
Conclusions:
Our longitudinal analyses confirm that differences in language performance emerge at around 12 months in HR infants who go on to develop ASD. It appears that early non-verbal communication skills make an important contribution to later language skills in infants at risk for ASD. Early deficits in these foundational language skills may be an important marker for later delays and offer an actionable target for early intervention.