Researchers at the UC Davis M.I.N.D. Institute have concluded that the seven- to eightfold increase in the number of children with autism born in California since 1990 cannot be explained by changes in how the condition is diagnosed or how statistics are gathered. Instead, the study, published in the current issue of the journal Epidemiology, suggests research on the cause of the neurodevelopmental disorder should shift to the environment.
"It's time to start looking for the environmental culprits responsible for the remarkable increase in the rate of autism in California," a co-author of the paper, Irva Hertz-Picciotto, said in a news release. "Right now, about 10 to 20 times more research dollars are spent on studies of the genetic causes of autism than on environmental ones. We need to even out the funding."
Hertz-Picciotto, an autism researcher and professor of environmental and occupational health and epidemiology, said the study is important because many researchers, state officials and advocacy organizations have been skeptical of the autism statistics in California. The incidence of autism in the state has increased from nine in 10,000 children (diagnosed by age 6) in 1990 to more than 44 in 10,000 for children born in 2000. The study was conducted using state health records as well as Census Bureau statistics, state birth certificates and vital statistics. The researchers correlated the cases of autism with birth records and excluded children not born in California. They calculated the rate of incidence in the population over time and examined the age of diagnosis.
The study concluded that migration was not the cause of the increase. In addition, inclusion of milder cases of autism only accounted for one-tenth of the increased number of cases. Only 24% of the increase could be attributed to an earlier age of diagnosis.
The M.I.N.D. Institute is currently conducting a study to look at the possible effects of metals, pesticides and infectious agents on neurodevelopment. "If we're going to stop the rise in autism in California, we need to keep these studies going and expand them to the extent possible," Hertz-Picciotto said.
Another study published recently suggests better ways to diagnosis autism may be on the horizon. Early diagnosis and treatment is considered crucial for the optimal development of children with autism. However, no diagnostic tests exist. Children are usually diagnosed using rating systems or checklists. The Centers for Disease Control and Prevention has fact sheets on autism screening and early signs of the disorder to encourage early diagnosis. However, Italian researchers say they hope babies can be screened for the disorder by using more objective measures.
The study, published in the December issue of the Journal of Proteome Research, found abnormal proteins in the saliva of autism patients that could eventually provide a clue for the molecular basis of the disorder and a marker for a subgroup of patients with autism. The researchers discovered that at least one of four proteins in 19 children with autism had significantly lower levels of phosphorylation, a process that allows proteins to function normally.
-- Shari Roan