WEDNESDAY, April 6, 2011 (HealthDay News) -- Poor children with autism are less likely than richer kids to have the condition diagnosed, but this disparity has decreased in recent years, according to a new study.
Researchers analyzed data on children in California and found that the average age of autism diagnosis fell from 5.9 years among children born in 1992 to 3.8 years for those born in 2000.
Of the 4,906,926 children born in California between 1992 and 2000, they found that 18,731 (0.38 percent) were diagnosed with autism. The prevalence of autism in the state increased from 29 per 10,000 children in 1992 to 49 per 10,000 children in 2000.
The study appears in the April issue of the American Sociological Review.
"At the height of rising prevalence, which involved children born between 1992 and 1995, kids whose parents had fewer economic resources simply weren't diagnosed as often as wealthier children -- wealthier kids were 20 to 40 percent more likely than poorer children to be diagnosed," study co-author Marissa D. King, an assistant professor of organizational behavior at Yale University's School of Management, said in a journal news release.
"Among children born in 2000, however, parental wealth alone had no effect on the likelihood that a child would be diagnosed," she added.
"As knowledge has spread about autism, information is now more evenly distributed across different kinds of communities," co-author Peter S. Bearman, a professor of social sciences at Columbia University and director of the university's Center for the Social Sciences, explained in the release. "It is also easier to find someone who can diagnose autism, so we no longer see these huge differences in rates of diagnosis. However, it appears that poor kids living in poor neighborhoods still are not being diagnosed."
The researchers found that between 1992 and 2000, a child in a poor family who lived in a more affluent neighborhood was about 250 percent more likely to be diagnosed with autism than a child from an equally poor family who lived in a poorer neighborhood.
When the researchers analyzed autism cases by severity, they found that children with less severe autism who were born in 1992 and lived in wealthier and more educated neighborhoods were 90 percent more likely to be diagnosed with the condition. By the end of the study period, that had decreased to 45 percent.
"Less severe cases, the kids who are the highest functioning, can often slip underneath the diagnostic radar in less affluent communities where the diagnostic resources are not as established," Bearman said. "If you're less severe, you might not be diagnosed because you don't seem to have a profound disability -- so you're just thought to be a weird kid."
While this study looked at children in California, the findings likely apply in other parts of the United States, the researchers said.
The U.S. National Institute of Neurological Disorders and Stroke has more about autism.