A new study led by a researcher at the University of Colorado finds that autism disorder rates in wealthy California counties are declining whereas rates in poorer counties with large numbers of Black and Hispanic families are increasing.
The data raises the possibility that parents in wealthier counties are successfully reducing environmental exposures that may contribute to autism risk, or taking other steps to curb its severity early on.
“While autism was once considered a condition that occurs mainly among Whites of high socioeconomic status, these data suggest that the brunt of severe autism is now increasingly being borne by low-income families and ethnic minorities,” said lead author Cynthia Nevison, an atmospheric research scientist with the Institute of Arctic and Alpine Research at the University of Colorado.
The study found that between birth years 1993 and 2000, autism prevalence increased steadily among all racial groups. But around 2000, the trajectories started to diverge: Prevalence among Whites in wealthy counties like Santa Clara (home to Silicon Valley) and from Monterey to the San Francisco coast started to decline. Meanwhile, the study found, incidence among Blacks has increased rapidly across California, marking the highest rates among any ethnic or racial group.
“There is an urgent need to understand what wealthy California parents are doing or have access to that may be lowering their children’s risk,” the authors conclude.
The full study, “California Autism Prevalence by County and Race/Ethnicity: Declining Trends Among Wealthy Whites,” was published on the website of the Journal of Autism and Development Disorders. It may be accessed here.