Attention Deficits On the Continuous Performance Test in Youths with Autism Spectrum Disorders and Their Unaffected Siblings

Background: Autism is a neurodevelopmental disorder with characteristic neuropsychological functioning. Evidence supports executive dysfunction in individuals with autism, but results regarding attention deficit were inconsistent across studies. Little is known about the attention in unaffected siblings of probands with ASD and differential attention capacity between autistic disorder and Asperger’s disorder.

Objectives:  This study aimed to compare the attention capacity of probands with autism spectrum disorders (ASDs, including autistic disorder and Asperger’s disorder), their unaffected siblings, and typically developing youths.

Methods:  We assessed 354 probands, aged 10.96±3.15 (male, 90%), diagnosed with autistic disorder (n = 216) or Asperger’s disorder (n = 138) according to the DSM-IV criteria, 287 unaffected siblings, and 255 typically developing youths (aged 11.78±2.25; male 80%) using the Continuous Performance Test (CPT) and a questionnaire for symptoms of attention-deficit hyperactivity disorder (ADHD). Generalized linear model was used to compare the CPT performance and ADHD symptoms among probands with autism, probands with Asperger’s disorder, and typically developing youths. A mixed model was applied to compare the probands with ASDs, unaffected siblings, and typically developing youths.

Results:  Probands with ASDs had more omission errors, perseverative response, greater reaction time (RT), and RT standard deviation than typically developing children. The significance remained after adjusting for age and sex. The severity of ADHD and ASD symptoms was significantly associated with impaired CPT performance in probands with ASD. Probands with ASD had significantly more ADHD symptoms than unaffected siblings and typically developing children. Unaffected siblings had significantly higher RT standard deviation and variability than typically developing youths.

Conclusions:  Our findings support impaired focused attention and vigilance in youths with ASDs, particularly those with autistic disorder. Although unaffected siblings did not show more severe ADHD symptoms, they had impaired focused attention assessed by the CPT. This finding implies that impaired focused attention may serve as one of potential endophenotypes for genetic studies in ASDs.