I have come across two studies about the causes of Autism in CA [as in California (US), not as in Canada] that are worthy of note. First, there’s a provactive story about an epidemiological study of the relationship between insecticides sprayed on agricultural fields and the incidence of Autism in CA. Second, there’s a study about increases in the identification of Autism in CA showing that much of the increase can be explained by changes in diagnostic labelling.
Is some of the increase in the identification of children with autism the result of changes in how the diagnostic label is applied? The factsheet about the prevalence of Autism by Lisa A. Croen and colleagues is available. Here’s an overview of that study:
The Changing Prevalence of Autism in California
A large study was conducted over eight successive years of CA births to examine changes in the observed rate of autism among children who are clients of the Department of Developmental Services and their Regional Centers. We sought to evaluate the degree to which improvements in detection and changes in diagnostic practices contribute to changes in the rate of autism for DDS/RC clients.
Children born between 1987-1994 with a diagnosis of autism (with or without mental retardation (MR) were identified from the electronic client files maintained by DDS/RC. To evaluate the role of diagnostic substitution, children with a diagnosis of unexplained MR without autism were also identified. A total of 5,038 children with a diagnosis of full-syndrome autism, autistic disorder and 11,114 children with a diagnosis of unexplained MR without autism were identified from 4,590,333 California births.
Over the eight birth years, the prevalence rate of autism for children enrolled with DDS/RC increased an absolute change of 9.1 per 10,000. During the same period, the prevalence rate of unexplained MR without autism for children enrolled with DDS/RC decreased an absolute change of 9.3 per 10,000. These changes in rate were not influenced by changes in demographic characteristics such as maternal age, race/ethnicity, maternal education, child gender or whether twins or multiple births.
These data suggest that improvements in detection and changes in diagnostic practices may account for much of the increase in autistic disorder observed among DDS/RC clients. Whether there has also been a true increase is not known. These data clearly demonstrate that autism is much more common than previously believed.
The full report of the second study was not yet available when I scoured the sit (or I didn’t scour it thoroughly enough. Howevere, here’s a snippet about the second study from an article by Marla Cone of the Los Angeles Times:
Women who live near California farm fields sprayed with organochlorine pesticides may be more likely to give birth to children with autism, according to a study by state health officials to be published today.
The rate of autism among the children of 29 women who lived near the fields was extremely high, suggesting that exposure to the insecticides in the womb might have played a role. The study is the first to report a link between pesticides and the neurological disorder, which affects one in every 150 children.
But the state scientists cautioned that their finding is highly preliminary because of the small number of women and children involved and lack of evidence from other studies.
“We want to emphasize that this is exploratory research,” said Dr. Mark Horton, director of the California Department of Public Health. “We have found very preliminary data that there may be an association. We are in no way concluding that there is a causal relationship between pesticide exposure of pregnant women and autism.”
Links: Ms. Cone’s story appeared under the headline, “Pesticide link to autism suspected
A state study suggests two farm sprays may raise chances of having a child with the disorder” and is available here. The factsheet about the study by Ms. Croen, Judith K. Grether, Jenny Hoogstrate, and Steve Selvin Croen is available here. For earlier discussion on EBD Blog of some of these issues, see Autism not epidemic, ASD prevalence in UK, etc.
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