Autism Spectrum Disorder, Intellectual Disability, and Delayed Walking

Area of Science:

• Developmental Pediatrics
• Neurodevelopmental Disorders
• Child Psychology

Background:

• Delayed independent walking is common in intellectual disability (ID).
• Autism spectrum disorder (ASD) frequently co-occurs with ID, but delayed walking is less frequently reported in ASD.
• This study investigates the link between delayed walking and ID severity in children with and without ASD.

Purpose of the Study:

• To examine the relationship between delayed walking and intellectual disability severity in children diagnosed with autism spectrum disorder (ASD) compared to children with other diagnoses.
• To determine if the association between intellectual disability and delayed walking differs between children with ASD and those without ASD.

Main Methods:

• Utilized data from 1185 children (ages 4-12 years) with ASD (n=903) and non-ASD (n=282) diagnoses.
• Assessed nonverbal IQ (NVIQ) and retrospectively collected age of walking using the Autism Diagnostic Interview-Revised.
• Employed Cox proportional hazards models to analyze the relationship between diagnostic group, NVIQ, and delayed walking (onset ≥16 months).

Main Results:

• Children with ASD were less likely to exhibit delayed walking compared to non-ASD groups.
• This difference was more pronounced at lower levels of nonverbal IQ (NVIQ).
• For instance, at NVIQ <70, 31% of ASD children had delayed walking versus 60% of non-ASD children.

Conclusions:

• Lower IQ scores correlated with increased late walking in both ASD and non-ASD groups.
• However, children with low IQ were more prone to delayed walking in the absence of ASD.
• This indicates potentially distinct etiological pathways for intellectual disability in children with and without ASD.