Upper-income parents are more likely to have children with autism, according to a University of Wisconsin-Madison study. The findings suggest either the genetics or the lifestyles of wealthier people predispose their children to autism.
Researchers have spent decades trying to untangle the factors that cause autism. Since the 1940s, scientists noticed wealthier and more educated families had children with the disorder, said Maureen Durkin, a UW-Madison epidemiologist and lead author of the study.
But while some U.S. studies found a link, others done in Scandinavia found no connection between autism and social class, Durkin said. Yet those countries also have social safety nets and universal health care, so rich and poor alike can get to the doctor’s office for a diagnosis of autism. That led some researchers to pursue whether there were differences in rates of diagnosis in the U.S., rather than rates of the underlying disorder.
The findings were published July 12 in PLoS One.
To see whether autism was more prevalent among the wealthy, Durkin combined neighborhood census data on socioeconomic status, which includes education, profession and income level, with data from the Centers for Disease Control and Prevention’s Autism and Developmental Disabilities Monitoring Network. The surveillance network uses school records to identify all 8-year-old children – even those who had no formal diagnosis – with the range of social, behavioral and language problems classified as autism spectrum disorder. This tracking method adjusts for the possibility that the poor are less likely to be diagnosed, Durkin said.
Of over half a million children, 3,680 had the disorder. Affluent youngsters were almost twice as likely as the poorest children to have autism. The poorest neighborhoods did have lower rates of diagnosis. But even among children with no autism diagnosis, the richest children displayed the behaviors and signs of autism 39% more often those in the poorest neighborhoods.
“The findings are very significant,” said Lisa Croen, an epidemiologist with Kaiser Permanente’s Autism Research Group in California. The study shows differences between diagnosis rates can’t be the whole story.
“Every race and ethnicity group, they saw this gradient. It suggests something else is going on,” she said.
But that something else remains a mystery.
“We can demonstrate that there is this association. It’s statistically significant, and it’s there, but we really can’t show why it’s there,” Durkin said.