"Environmental, State-Level Regulatory Factors Affect Incidence of Autism & Intellectual Disability"

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http://www.ploscompbiol.org/article/info%3Adoi%2F10.1371%2Fjournal.pcbi.1003518

Environmental and State-Level Regulatory Factors Affect the Incidence of Autism and Intellectual Disability

Andrey Rzhetsky, Steven C. Bagley, Kanix Wang, Christopher S. Lyttle, Edwin H. Cook Jr, Russ B. Altman, Robert D. Gibbons
Published: March 13, 2014DOI: 10.1371/journal.pcbi.1003518

Abstract

Many factors affect the risks for neurodevelopmental maladies such as autism spectrum disorders (ASD) and intellectual disability (ID). To compare environmental, phenotypic, socioeconomic and state-policy factors in a unified geospatial framework, we analyzed the spatial incidence patterns of ASD and ID using an insurance claims dataset covering nearly one third of the US population. Following epidemiologic evidence, we used the rate of congenital malformations of the reproductive system as a surrogate for environmental exposure of parents to unmeasured developmental risk factors, including toxins. Adjusted for gender, ethnic, socioeconomic, and geopolitical factors, the ASD incidence rates were strongly linked to population-normalized rates of congenital malformations of the reproductive system in males (an increase in ASD incidence by 283% for every percent increase in incidence of malformations, 95% CI: [91%, 576%], p<6×10−5). Such congenital malformations were barely significant for ID (94% increase, 95% CI: [1%, 250%], p = 0.0384). Other congenital malformations in males (excluding those affecting the reproductive system) appeared to significantly affect both phenotypes: 31.8% ASD rate increase (CI: [12%, 52%], p<6×10−5), and 43% ID rate increase (CI: [23%, 67%], p<6×10−5). Furthermore, the state-mandated rigor of diagnosis of ASD by a pediatrician or clinician for consideration in the special education system was predictive of a considerable decrease in ASD and ID incidence rates (98.6%, CI: [28%, 99.99%], p = 0.02475 and 99% CI: [68%, 99.99%], p = 0.00637 respectively). Thus, the observed spatial variability of both ID and ASD rates is associated with environmental and state-level regulatory factors; the magnitude of influence of compound environmental predictors was approximately three times greater than that of state-level incentives. The estimated county-level random effects exhibited marked spatial clustering, strongly indicating existence of as yet unidentified localized factors driving apparent disease incidence. Finally, we found that the rates of ASD and ID at the county level were weakly but significantly correlated (Pearson product-moment correlation 0.0589, p = 0.00101), while for females the correlation was much stronger (0.197, p<2.26×10−16).

Author Summary

Disease clusters are defined as geographically compact areas where a particular disease, such as a cancer, shows a significantly increased rate. It is presently unclear how common such clusters are for neurodevelopmental maladies, such as autism spectrum disorders (ASD) and intellectual disability (ID). In this study, examining data for one third of the whole US population, the authors show that (1) ASD and ID display strong clustering across US counties; (2) counties with high ASD rates also appear to have high ID rates, and (3) the spatial variation of both phenotypes appears to be driven by environmental, and, to a lesser extent, economic incentives at the state level.

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Citation: Rzhetsky A, Bagley SC, Wang K, Lyttle CS, Cook EH Jr, et al. (2014) Environmental and State-Level Regulatory Factors Affect the Incidence of Autism and Intellectual Disability. PLoS Comput Biol 10(3): e1003518. doi:10.1371/journal.pcbi.1003518

Received: September 25, 2013; Accepted: February 1, 2014; Published: March 13, 2014

http://www.nlm.nih.gov/medlineplus/news/fullstory_145100.html

More Evidence Environmental Exposures Contribute to Autism
Where birth defects increased, so did diagnoses of the developmental disorder, study showed

Thursday, March 13, 2014

THURSDAY, March 13, 2014 (HealthDay News) -- A large U.S. study suggests environmental pollution might be contributing to autism risk, although the specific culprit toxins remain unknown.

Researchers analyzed medical records and found a correlation between U.S. counties' autism rates and their rates of genital birth defects in boys, which could be a sign of some common environmental contributors.

However, the findings, which were reported March 13 in the journal PLoS Computational Biology, do not prove that any particular environmental exposure directly raises the risk for the developmental disorder, experts said.

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