The risk of a later diagnosis of autism may be slightly increased in young children who have asthma, according to a new study. More evidence of correlations among immune function, physiology, and behavioral/developmental conditions is provided in the study.
Autism spectrum disorders (ASDs) have been described as enigmatic conditions that have their origins in the interaction of genes and environmental factors. Genes associated with autism may be important in inflammation and in innate immune pathways, including pathways for susceptibility to asthma, research shows. This had led to a suggestion of an association between ASDs and allergic disorders, but epidemiological evidence regarding asthma remains limited.
Researchers from Taiwan conducted a nationwide, population-based, prospective cohort study hypothesizing that asthma in infancy or toddlerhood increases the risk of ASDs, based on an analysis of the National Health Insurance Research Database in Taiwan. The same research group previously examined the comorbidity of allergic and autoimmune diseases in cases of autism and more recently linked early-life asthma with a heightened risk of subsequent attention-deficit/hyperactivity disorder.
In the new study, the patients included more than 2000 asthmatic infants and children up to age 3 years with a physician diagnosis of asthma who were matched by age and sex with more than 8500 control patients with no asthma and no recorded history of psychiatric disorder. The researchers looked for any subsequent evidence of a psychiatrist diagnosis of an ASD (based on ICD-9 criteria) up to 8 years later.
“We identified cases of ASD that occurred near the end of the follow-up period, determining that asthmatic infants and children exhibited a higher accumulative incidence rate of ASD (1.7%) than did the controls (1.3%),” stated the researchers, noting that this difference was statistically significant.
After adjusting for age at enrollment; sex; level of urbanization; and comorbid allergic diseases, such as allergic rhinitis and atopic dermatitis, asthmatic infants and children exhibited an elevated risk of developing ASD that was twice as much as that in the nonasthmatic patients.
The levels of other allergic diseases also were more frequently reported for the asthma group. Also, patients in the asthma group were slightly more likely to be living in urban areas than controls, although urbanization was not reported to increase the risk of ASD significantly.
Asthmatic patients tended to receive a diagnosis of ASD later (5.6 years) than those who received a diagnosis of ASD in the control group (4.5 years), but this difference was not statistically significant.
“This prospective study indicated a temporal relation between asthma and subsequent ASD diagnosis, supporting the immune hypothesis of ASD pathogenesis,” concluded the researchers. They noted that further studies are required “to clarify the probable interactional effects between these disorders and define a homogenous ASD subgroup.”
The researchers reported their results in the April 2014 issue of Research in Autism Spectrum Disorders.