Increased risk of autism spectrum disorder among early life asthma patients: An 8-year nationwide population-based prospective study

• Research has suggested an association between ASD and allergic disorders.
• The incidence of ASD among asthmatic infant and children was investigated in this nationwide population-based cohort study.
• Asthma in early life is a risk factor for subsequent ASD diagnosis.
• The results support the immune hypothesis of ASD pathogenesis.

Previous research has suggested an association between autism spectrum disorder (ASD) and allergic disorders, but epidemiological evidence regarding asthma remains limited. We conducted a nationwide population-based prospective cohort study (1:4 case:control patients, age- and gender-matched), hypothesizing that asthma in infancy or toddlerhood increased the risk of ASD. The participants comprised 2134 asthmatic infants and children and 8536 controls aged 0–3 years in 2002. We identified cases of ASD that occurred near the end of the follow-up period (December 31, 2010), determining that asthmatic infants and children exhibited a higher accumulative incidence rate of ASD than did the controls (1.3% vs 0.7%, P = .007). After adjusting for age at enrollment, gender, level of urbanization, and comorbid allergic diseases (i.e., allergic rhinitis and atopic dermatitis), asthmatic infants and children exhibited an elevated risk of developing ASD (hazard ratio: 2.01, 95% confidence interval: 1.19–3.40). This prospective study indicated a temporal relation between asthma and subsequent ASD diagnosis, supporting the immune hypothesis of ASD pathogenesis. Further studies are required to clarify the probable interactional effects between these disorders and define a homogenous ASD subgroup.