Younger siblings of children with autism (Sibs-ASD) often are studied longitudinally to explore early markers of ASD due to heightened risk for the disorder. However, school-age outcome in such well-characterized cohorts of children has rarely been examined, despite literature indicating that Sibs-ASD who do not themselves have ASD are at risk for cognitive, language, and social difficulties. In addition, evidence for executive functioning (EF) deficits in relatives of individuals with ASD exists. Thus, we examined the neurocognitive profiles of five-year-old Sibs-ASD and age-matched siblings of typically developing children (Sibs-TD) who previously participated in a longitudinal study of early social and communication development.
To examine EF abilities and their relation to ASD features at school age in a group of Sibs-ASD who did not receive a diagnosis of ASD themselves, in comparison to a group of Sibs-TD.
23 Sibs-ASD and 19 Sibs-TD were evaluated between the ages of 5 and 7 years (mean CA: Sibs-ASD=65.55 months; Sibs-TD=64.84 months).These children represent a subset of children followed longitudinally since age 15 months on average to examine early risk factors for ASD. . At the school-age assessment, all children were administered select subtests (Auditory Attention, Inhibition-Naming and Inhibition-Inhibition, Statue) from the NEPSY-II to examine EF abilities; an EF composite score was derived by averaging the four subtest scores, all of which were highly correlated (r>.401, p<.01).Parents of 18 Sibs-ASD completed the ADI-R to assess ASD symptoms. Between group comparisons were conducted using independent sample t-tests for the EF composite and each NEPSY subtest score. Bivariate correlations were conducted between EF composite and subtests and ADI-R domain scores in the Sibs-ASD group to explore the relations among EF abilities and ASD features.
Sibs-ASD performed significantly lower than Sibs-TD on the overall EF composite score (p=.007), as well as on the combined scaled score (p=.008) and raw omission errors (p=.037) from the Auditory Attention test and the combined scaled score from the Inhibition-Naming subtest (p=.025). Group differences approached significance on the Statue subtest total scaled score (p=.067), but were not found on the Inhibition-Inhibition subtest. In Sibs-ASD, significant correlations were found between the EF composite and the Communication (r=-.486, p=.041) and Restricted Interests and Repetitive Behavior (r=-.514, p=.029) domains of the ADI-R. While the EF composite did not correlate with the ADI-R social domain, greater number of omission errors on the auditory attention task was correlated with greater social impairment on the ADI-R (r=.689, p=.002).
Sibs-ASD who do not themselves have ASD diagnoses nevertheless show subtle but significant differences from Sibs-TD at age five years. Specifically, they show differences in EF abilities, which are related to broader, subclinical ASD symptoms. Executive functioning and the brain regions coordinating these skills continue to mature throughout childhood, and subtle deficits may have implications for later social and academic success in this vulnerable population. Thus, future directions include exploring various EF abilities in Sibs-ASD during adolescence and adulthood.
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