Parental Exposure to Occupational Asthmagens and Risk of Autism Spectrum Disorders in the Study to Explore Early Development

Background:   While there is evidence that prenatal environmental factors may contribute to the development of autism spectrum disorders (ASDs), few specific environmental factors have been elucidated.  Some environmental and occupational exposures can trigger immune responses.   Specifically, asthmagens are agents that trigger an asthmatic response, which may activate maternal immune systems.  There is evidence that activation of the maternal immune system during pregnancy may be linked with ASDs.

Objectives:   We seek to determine if mothers of children with ASD were more likely to be exposed to asthmagens during pregnancy than mothers of children with non-ASD developmental delays or typically developing children.

Methods:   We are using data from the Study to Explore Early Development (SEED), a multi-site, case-control study in the United States.  During a phone interview mothers were asked about jobs held from 3-months prior to conception until the birth of the child or end of breastfeeding.   For each job mothers were asked to report job title, employer, location, job start and end date, hours per week, type of business, and main duties.  All reported jobs were coded according to the categories of the International Standard Classification of Occupations (ISCO-88).   We used an asthma-specific job exposure matrix (JEM) developed by Kennedy et al. to estimate occupational exposures to asthmagens.  For each ISCO job code, the JEM specifies whether or not there is a high probability of asthmagen exposure.  We will use logistic regression models to examine the association between maternal asthmagen exposures and ASDs, adjusting for sociodemographic covariates.

Results:   Our analysis includes 687 ASD cases, 1056 children with non-ASD developmental disabilities, and 965 general population controls whose mothers answered questions about occupational history during pregnancy.  2033 (75%) participants reported at least one job.  The average number of jobs per mother was 1.2 among mothers reporting jobs.  Mothers of general population controls were more likely to report a job than mothers of children with ASDs or non-ASD developmental delays.  Among mothers reporting a job, 14% were exposed to occupational asthmagens according to the JEM.  The findings described here are preliminary.  Results comparing asthmagen exposure in the case and control groups will be presented.

Conclusions: Evidence suggests that environmental exposures influence ASD risk.  Only a few studies have looked at occupational exposures in relation to ASDs, so we are examining workplace exposure to asthmagens in a large case-control study with detailed phenotypic data on cases.