Longitudinal Predictors of Receptive and Expressive Language Outcomes at 6 Years in Younger Siblings of Children with ASD

Background:   During the second and third years of life, younger siblings of children with ASD have a higher risk of developmental difficulties, including reduced receptive and expressive language abilities.

Objectives:  To explore receptive and expressive language functioning in younger siblings of children with ASD, at school-age, and to identify early predictors of these outcomes.

Methods:  Receptive and expressive language performance in 157 younger siblings of children with ASD (high risk, HR) and 33 low risk (LR) controls were assessed at least once between 4 and 12 years of age, using the Test of Language Development (TOLD), and at least once between 6 and 36 months (6,14,18,24,30, and/or 36 months), with the Autism Diagnostic Observation Schedule (ADOS; Lord et al., 2002, 2012) and Mullen Scales of Early Learning (MSEL; Mullen, 1995). Based on the 36-month assessments, siblings were subgrouped into ASD (HR-ASD, n=39), broad autism phenotype (BAP) (HR-BAP, n=73), and typically developing (HR-TD, n=45). The three HR groups and LR group were compared at each time point between 6 and 36 months, and the time point closest to 72 months (±72months). Analyses also examined predictive relationships with the ADOS and MSEL.

Results:  Analyses of variance (ANOVAs) with the 3 HR groups and LR group revealed no significant differences at 6 months. ANOVAs at each subsequent time point revealed significant between-group differences (all p’s<.001). LR and HR-TD groups did not differ significantly on receptive or expressive language scores at any time point. In contrast, after 14 months, the HR-ASD group consistently demonstrated significantly lower receptive and expressive language than the HR-TD group (p’s≤.002). The HR-BAP group also demonstrated significantly lower receptive language at 14,24,30,36, and ±72 months (p’s ≤.04) and expressive language at 14,18,24,36, and ±72 months (p’s≤.04) in comparison with the HR-TD group. To examine early predictors, multiple linear regression models were generated for receptive and expressive language outcomes at ±72 months, using ADOS Communication+Social scores and MSEL Expressive Language scores at 24 months as predictors. The predictors accounted for a significant amount of variance in receptive and expressive language scores at ±72 months, p<.001. Both predictors had a unique effect on receptive language (positive for MSEL, p<.001; negative for ADOS, p=.03) and on expressive outcomes (positive for MSEL, p<.001; negative for ADOS, p<.01).

Conclusions:  Younger siblings of children with ASD as a group are susceptible to reduced receptive and expressive language functioning compared to LR children. However, this susceptibility manifests differently based on 36-month diagnostic status: children meeting ASD or BAP criteria have the highest susceptibility to later lower language functioning. ADOS Communication+Social scores and MSEL Expressive Language scores at 24 months appear to be predictive of later language outcomes.