Kate Hoffman, Marc G. Weisskopf, Andrea L. Roberts, Raanan Raz, Jaime E. Hart, Kristen Lyall, Elin M. Hoffman, Francine Laden, Verónica M. Vieira

Data indicate that autism spectrum disorder (ASD) prevalence may be increasing and varies geographically. We investigated associations between residential location and ASD in the children of Nurses' Health Study II women in order to generate hypotheses about social and environmental factors related to etiology or diagnosis. Analyses included 13,507 children born from 1989-1999 (486 with ASD). We explored relationships between ASD and residential location at both birth and age 6 years (i.e. closer to average diagnosis age). Generalized additive models were used to predict ASD odds across the US. Children born in New England were 50% more likely to be diagnosed with ASD compared to children born elsewhere in the US. Patterns were not explained by geographic variation in maternal age, birth year, child's sex, community income or prenatal exposure to hazardous air pollutants, indicating that spatial variation is not attributable to these factors. Using the residential address at age 6 produced similar results; however, areas of significantly decreased ASD odds were observed in the Southeast, where children were half as likely to have ASD. These results may indicate that diagnostic factors are driving spatial patterns; however, we cannot rule out the possibility that other environmental factors are influencing distributions.