Clusters in California
Two new studies take a look at what appear to be unusually high concentrations of children with autism in certain parts of California.
The first study, published in the journal Autism Research by a team from the University of California, Davis, identified ten autism hotspots or clusters in the Los Angeles and San Francisco regions, where autism rates were twice as high as in surrounding areas. The lead author, Irva Hertz-Picciotto, said that the hotspots could probably be explained by the fact that parents had a higher level of education in these areas.
“In the U.S., the children of older, white and highly educated parents are more likely to receive a diagnosis of autism or autism spectrum disorder. For this reason, the clusters we found are probably not a result of a common environmental exposure. ” said Dr. Hertz-Picciotto.
Still, Hertz-Picciotto does not rule out the possibility that there might be environmental exposures associated with higher levels of education and plans to investigate that possibility.
The second study by a team from Columbia University was published this month in Health & Place. This study looked at clusters based on where children were born, as opposed to their current address. The team, led by sociologist Peter S. Bearman, identified a large cluster in the Los Angeles area where children had four times the risk of being diagnosed with autism than children born elsewhere in the state. The cluster was seen throughout the period studied: 1993-2000 and was associated with high property values. The authors suggest that the higher incidence could be due to “local environmental or social dynamics.”
Bottomline: Not clear from these studies that anything beyond social factors–higher income, higher education and therefore better access to treatment–explains the high concentration of autism cases in some parts of California.