Autism: Examining Rising Prevalence in Black and Hispanic Children
When the Centers for Disease Control and Prevention (CDC) released its biannual overview of autism prevalence in early 2018,
it reported that one in fifty-nine 8-year-olds (born in 2006) had an
autism spectrum disorder (ASD). This represented a 15% increase from the
rate of one in sixty-eight
described in the CDC’s 2016 and 2014 reports
(for 8-year-olds born in 2004 and 2002, respectively). A federal
snapshot of 3 through 17 year-olds in 2016 reported diagnosed autism in
one in thirty-six children—23% more than in 2014.
Despite the two-year jump in ASD prevalence, the CDC cast a positive spin on
its 2018 findings. Recognizing that white ASD prevalence had been
higher, in the past, than prevalence among other race/ethnicity groups,
the agency hypothesized that “white ASD prevalence had largely stabilized”
and praised the 15% increased prevalence as a reflection of “the
catch-up of Hispanics and blacks who had been historically
underascertained.” The media readily acquiesced to this worn-out
narrative, implying that latent autism cases had simply been waiting to
be discovered through more effective outreach and better screening.
According to PBS,
“[I]f it’s the case that the rate grew only because of better
diagnosis, that would mean that autism spectrum disorder isn’t becoming
more common among American children. Doctors are just better at spotting
it.”
Dissatisfied with the “better diagnosis” explanation, University of Colorado researcher Cynthia Nevison wrote of a 1000-fold increase in autism prevalence since the 1930s and a 25-fold increase since the 1970s in a December 2018 publication in the Journal of Autism and Developmental Disorders. Now,
Nevison and Rutgers researcher Walter Zahorodny—who regularly
contributes New Jersey data to the biannual CDC reports—have published
a new studycritiquing the “catch-up” hypothesis. Their analysis further undermines officials’ complacent narrative by highlighting upward ASD trends among black and Hispanic children above and beyond mere “catch-up”—as well as pointing to worsening racial/ethnic disparities.
Deep diving the autism data
The two researchers used the two best
datasets available to assess time trends in race-specific United States
autism prevalence. The first came from 18 years of annual reports
collected for the Individuals with Disabilities Education Act (IDEA),
which has tracked special education recipients (ages 3-21) since the
early 1990s, with breakdowns by race/ethnicity available for 3-5
year-olds; the most recent IDEA data are for 3 to 5 year-olds born in
2012–2014. The researchers compiled the second dataset across eight
biannual Autism and Developmental Disabilities Monitoring (ADDM) Network
reports; the ADDM Network is the ongoing CDC surveillance system that
reports every two years on ASD prevalence in children born 12 years
previously.
After a year of careful data analysis,
the researchers ascertained several interesting trends among 3 to 5
year-olds in the IDEA dataset:
- Among white children, ASD rates plateaued in the mid-2000s after 15 years of sharp increase; around birth year 2007, however, white ASD prevalence “resumed its climb” in many states.
- ASD prevalence increased continuously in black children, “catching up” to white prevalence by birth year 2008; from that year on, black ASD prevalence surpassed white prevalence in the majority of states, without a plateau.
- ASD prevalence also increased continuously among Hispanic children and, beginning in birth year 2007, grew faster than the other races in the clear majority of states. By birth year 2013, ASD prevalence among Hispanic children exceeded that among whites in one-third of states.
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ADDM data from nine states for birth
years 2002–2006 showed mixed trends for white children, depending on the
state, but for both black and Hispanic children, ASD prevalence
increased in six out of nine states. However, Georgia was the sole state
where the trends fully supported the CDC hypothesis of a stabilized
white ASD prevalence and black and Hispanic “catch-up.”
Discussing the plateau in white ASD
prevalence in the mid-2000s, the two researchers point out that it could
“suggest a stabilization of the environmental drivers of ASD…followed
by a new or increasing environmental insult after 2007.” They also
mention a recent study in California that
analyzed the issue of the white ASD plateau in greater depth, using
stringent data from the California Department of Developmental Services
(CDDS). While that study confirmed a slowdown in ASD prevalence among
privately insured (i.e., higher income) white children, the researchers
found that ASD rates among publicly insured (i.e., lower income) whites
actually continued to increase strongly and steadily through the 2000s.
Over the same decade, ASD prevalence for black children also increased
strongly—irrespective of type of insurance—and ended up exceeding white
prevalence by almost 40%. These provocative results suggest that
higher-income white parents may have some insights into ASD prevention.
Where’s the urgency?
In its zeal to celebrate better
screening and diagnosis, the CDC would do well to remember that early
diagnosis does not guarantee better outcomes. For example, a Canadian
study that looked at a form of epilepsy associated with ASD found that
“early diagnosis and treatment did not prevent ASD as an outcome.” And in a study just published out of Australia that looked at ASD disparities along
income lines (using immigration as a proxy), children of immigrants
from lower-income countries received their autism diagnosis at a younger
age than non-immigrant children but had a worse prognosis—including “an
increased risk of intellectual disability and poorer presentations in
the social and communication domains.”
Why aren’t public health researchers
pursuing prevention-related research questions instead? What will it
take to get the CDC to take the rising rates of autism seriously? In
contrast to the CDC’s apathy, Zahorodny, in 2018, shared concerns about
the reported 15% increase in ASD prevalence in 8-year-olds:
“This is a very significant change with[in] a relatively small period of time. …It’s very concerning, very alarming, very disappointing, very important to take into account and to acknowledge. …These estimates are not at all due to [a] changing definition of autism.… The increase in autism prevalence is pushed quite significantly by children with significant levels of impairment and with co-occurring cognitive impairments, so it’s not just slightly affected children that are making the estimates percolate upward. Autism is increasing across the board.”
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