California Autism Clusters Tied to Parents' Education, Not Environment

Jan. 9, 2010— -- Researchers have found clusters of autism in 10 areas around California -- but with no suggestion of a link to local pollution or other environmental exposures, they said.

Instead, the only consistent factor among the areas -- identified largely in Southern California and the San Francisco Bay region -- was a population of well-educated parents, Karla Van Meter of the University of California Davis and colleagues found.

In six of the clusters, a college-educated parent conferred a risk of autism that was more than four times as great as a parent who didn't graduate from high school, they reported online in Autism Research.

"At this point, we don't think that's due to differences in the actual rates," coauthor Irva Hertz-Picciotto, also of UC Davis, told MedPage Today.

The observational study determined autism cases through a database of state-sponsored developmental services, a system which relies on parents to voluntarily seek services.

Parents with higher education are likely to be better insured and more attuned to seek diagnosis and services for their autistic children than less-educated parents -- an effect seen in prior studies, the researchers said.

The clear-cut link with mom and dad's education should be reassuring to parents living in the cluster areas, Hertz-Picciotto said.

"There was such a uniform pattern across all of these clusters [linking higher education to autism rates]," she said. "This is really not something people should be worried about who are living in those areas."

The real concern was that local pollution sources, such as dumps or factories, would be associated with increased autism incidence, the researchers noted.

While autism clearly has a genetic component, the search for its cause has also turned up plenty of clues involving prenatal and early childhood environments, Hertz-Picciotto explained.

So her group applied a new cluster-detection technique to the addresses on birth certificates -- a location where late gestational or early neonatal exposures were likely to have occurred.