Invited by Frieden to speak at the briefing, Roithmayr respectfully disagreed with him.
“Only part of the increase is better diagnosis. Something is going on here that we don’t know,” Roithmayr said. He added that “we desperately need deeper and broader funding” for treatment of the disorder and research on its causes.
In recent years, some groups have blamed autism’s rise on a preservative, thimerosal, that is no longer used in childhood vaccines and on the practice of giving infants multiple immunizations at a single visit. Research has ruled out both as a cause.
CDC has several studies underway assessing genetic, reproductive, environmental and behavioral variables associated with autism. One of them, the Study to Explore Early Development (SEED), is following 2,700 children and their families in six states, including Maryland.
As soon as the new prevalence estimate was announced, advocacy groups jumped on the news to promote their theories and agendas.
“These stunning new figures are a call to action among our elected leaders to minimize our children’s exposures to mercury and other toxic chemicals,” said Ken Cook of Environmental Working Group. “Upending the federal government’s approach to regulating toxic chemicals and putting tough emissions standards in place at power plants are two good places to start.”
Research suggests that some families have a genetic predisposition for autism and that parental age may play a role. There’s also evidence the condition may begin before birth and be the end result of a disordered process of brain development. A recent study in mice showed that an autism-like disorder could be reversed by bone-marrow transplantation that restored a certain type of cell, called microglia, to the brain.
In the CDC study, surveyors looked for 8-year-olds who were getting special education services or were being treated at specialty hospitals or medical units for one of three “autism-spectrum” disorders. The children’s records were then reviewed by clinical experts to see that they actually fit the diagnosis. The children themselves, however, were not examined.
Among the children with a diagnosis in their medical records, 44 percent had autistic disorder (which is at the severe end of the spectrum); 47 percent had pervasive developmental disorder; and 9 percent had Asperger syndrome. The prevalence of all three subtypes has been rising in about the same proportion, according to the survey.
If the rising prevalence represents an actual increase of the disorders — and is not the consequence of finding previously undiagnosed cases — that suggests there may be environmental exposure or demographic change (such as older parenthood) that is responsible, because a population’s genetic background wouldn’t change over a few decades.
The autism prevalence in Maryland is 12.9 per 1,000 children at age 8, slightly above the national average. The disorder is slightly more common in white children than in blacks, but twice as common in whites as in Hispanics.
The survey was done in six counties: Anne Arundel, Baltimore, Carroll, Cecil, Harford and Howard. It did not include Baltimore City, where the three hospitals with special programs for the metropolitan area are located.
Lee, who is affiliated with Johns Hopkins University’s Bloomberg School of Public Health, said that Baltimore City was surveyed the first year of the survey but was dropped because principals in the city schools didn’t have enough time to cooperate with researchers.