Risk of autism spectrum disorders after infantile spasms: a population-based study nested in a cohort with seizures in the first year of life

Purpose: No population‐based study has investigated the risk of autism spectrum disorders (ASDs) in children after unprovoked seizures with onset in the first year of life. Our objective was to determine whether infantile spasms were related to risk of ASD as compared to unprovoked seizures with onset in the first year of life after adjusting for symptomatic origin of seizures. Methods: This is a population‐based case‐control study nested in a cohort of children with unprovoked seizures in the first year of life. The cohort comprised 95 children, 34 boys and 61 girls. Cases were defined as children with ASD, controls were without ASD, and exposure was a history of infantile spasms. The Mantel‐Haenszel test and logistic regression were used to calculate the odds ratio (OR) and 95% confidence intervals (CI). Results: The crude OR for ASD associated with infantile spasms was 5.53 (95% CI 1.25–23.06). Stratification on age and gender did not change the OR. The OR for ASD associated with infantile spasms adjusted for symptomatic seizures was 1.55 (95% CI 0.33–7.37), while the OR for ASD associated with symptomatic seizures adjusted for infantile spasms was 8.73 (95% CI 1.88–40.54). Restriction to mental age 24 months or higher yielded higher ORs. Discussion: Infantile spasms predicted high risk for ASD, but this was to a large extent explained by the association of ASD with symptomatic origin of seizures.