Autism Prevalence is Declining in California Counties With Higher Incomes

by Kate Raines

Published April 12, 2020 | Health, Immune & Brain Disorders

Story Highlights

• Researchers have documented that the prevalence of autism spectrum disorder (ASD) is declining in financially secure, predominantly Caucasian communities in California, in contrast to steeply rising rates seen in counties where many families of every race are living in poverty.
• Researchers did not determine whether the observed declines are related to accessibility of health services, decreased reliance on department of Department of Developmental Services or variations in lifestyle choices.
• Some of the life choices that might affect ASD risk and may be more available to families with higher incomes include healthier diets, earlier and more concentrated health care interventions, lower exposure to environmental toxins and chronic stress; and use of fewer vaccines, as “vaccine hesitancy” is also more common among this demographic.

Higher income, primarily Caucasian communities in California were once considered to have a greater number of children with autism spectrum disorders (ASD).¹ The differences in prevalence of ASD among different communities were often attributed to socioeconomic factors influenced by adequate or inadequate access to healthcare services, which impacted evaluation, diagnosis and treatment of ASD.² A recent study out of California shows that autism rates are declining among Caucasian families with higher incomes, while prevalence of ASD among those families of all races living in poverty are increasing.

Details Provide New Insight Into ASD Prevalence

Using data from California’s Department of Developmental Services (DDS), the researchers looked at children born between 1993 and 2013 in the 36 most populous counties in California. They found that, while rates of ASD continued to climb among all children with birth years up until 2000, the numbers subsequently diverged, flattening or decreasing among Caucasians living in communities with higher incomes and continuing to climb among both Caucasians and Hispanics living in poorer counties.
In most of California’s counties, ASD incidence in Asian children began as comparable to or lower than that for Caucasians in birth year 1993 but was comparable to or higher than that for Caucasians by birth year 2013. For the minority of African American children, insufficient data were available for most counties.
Where prevalence could be assessed, ASD rates were higher than for Caucasians in five counties, comparable to Caucasians in two other areas and slightly lower than for Caucasians in Los Angeles.³ For African Americans in California overall, the ASD incidence rate of 1.8 percent is in keeping with other data showing that autism is increasing markedly among African Americans.⁴
Breaking down the data by county provided details about the decelerating but still continuing rise in incidence of ASD among Caucasians in California. The study showed that, rather than a decelerating increase among Caucasians as a whole, there appear to be steep increases in lower income counties contrasting with declines in higher income counties. The authors concluded that starting in about 2000, Caucasian parents with higher incomes were either opting for private services in lieu of DDS or were making environmental exposure and lifestyle changes that lowered their children’s risk for ASD.
The study authors have proposed several possible scenarios. They suggest that higher income and education may be associated with better prenatal and postnatal practices, as well as improved birth outcomes that might lower the risk of ASD. Parents with higher incomes also may have access to early and proactive interventions that either change the diagnosis or decrease the severity of ASD, which could make their children ineligible for involvement with DDS, a state social service that tends to focus on the most severely affected children. The researchers also speculated about whether families with higher incomes are relying on behavioral health services available through private insurance or channels, while poorer families must rely on DDS.
Lead researcher Cynthia Nevison said, “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.”

Lifestyle Choices May Contribute

Other lifestyle choices that can limit immune inflammation and oxidative stress, both strong markers associated with ASD, include healthy dietary choices, avoidance of environmental toxins, and reduction of chronic stress, all of which may be more accessible to the wealthy.
Another factor common to the same demographic of parents—Caucasian, well educated, and financially secure—is the tendency to question vaccine safety and effectiveness, described by some as “vaccine hesitancy.” Though not mentioned by the researchers of this particular study, parents who question vaccination also “tend to be better educated.” A recently published study looking at communities in Texas found that parents who are “college-educated, live in suburban or urban areas, have higher median incomes and are ethnically white are less likely to vaccinate their children.”⁵
The authors of the California study concluded that further study is needed to determine whether their findings will hold true in other areas of the country.

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