The apparent new increase in autism may not reflect the actual prevalence | Spectrum



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Unexpected effects: The order of questions in prevalence surveys may affect the estimate.

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New statistics on the prevalence of autism in the United States suggest a dramatic increase in the number of children with the disease. But it is unlikely that these numbers reflect a true increase in prevalence, experts say.

The prevalence of autism in the United States has increased from 1 in 91 children in 2009 to 1 in 40 in 2017, according to the results of the survey published today in the United States. pediatrics1. The study also shows that the disease is most often diagnosed in white children, city-dwellers and those with government-funded insurance.

Results are based on telephone or in-person interviews with parents of 88,530 children aged 3 to 17, collected by the Centers for Disease Control and Prevention (CDC) in the United States as part of its national survey on health talks. Figures are higher than the prevalence 1 of 59 reported by the CDC last year; This study analyzed the 2014 health and education records for children in 11 states – generally considered more reliable than parental surveys.

An important part of this increase is likely due to the growing awareness of the disease and the improvement of autism child identification systems, said chief investigator Benjamin Zablotsky, a statistician of health at the CDC.

The way in which the survey asks and asks a question about autism – asking parents if a health professional has already told them that their child has autism – may also affect the estimates of prevalence, he says2.

In 2011, the CDC expanded the survey question to ask about "Autism Spectrum Disorder" in addition to "Autism." In 2014, the question focused on "Autism, Asperger's Disorder, Autism Spectrum Disorder or Autism Spectrum Disorder". year also reversed the order of questions, asking parents first about autism, then about developmental delays – the reverse of the order of previous surveys.

As a result, the survey may have revealed an approximately 80% increase in the prevalence of autism. The new survey maintains the same order.

"We recognize without a doubt that this could have partly accounted for the increase in prevalence, at least in the estimation," Zablotsky said.

Demographic divisions:

The new survey found that the prevalence of developmental disorders had increased by 10% between 2009 and 2017, mainly due to autism (122% increase), hyperactivity disorder with deficiency disorder. Attention (13%) and intellectual disability (26%). The prevalence of other developmental disorders, including hearing loss and seizures, decreased by 13%.

According to reports from parents, about 1 in 51 white children had been diagnosed with autism during the nine-year study period, compared with 1 in 65 black children and 1 in 75 Hispanic children. also show that 1 out of 56 children in urban areas had a diagnosis of autism, compared to 1 in 64 children in rural areas. The most important disparities concern the insurance status of the child: about 1 out of 45 children on public insurance had a diagnosis of autism, compared to 1 in 69 of those with private insurance and 1 in 104 non-insured children. insured; this may be due to the fact that children who have been diagnosed with autism are eligible for assistance under public insurance.

Higher education levels among mothers indicate a lower prevalence of all childhood conditions examined in the survey, with the exception of autism and haze Attention Deficit Hyperactivity Disorder (ADHD). Maureen Durkin, a professor in population health sciences and pediatrics at the University of Wisconsin-Madison, reports an increasing number of diagnoses of both conditions. Durkin was not involved in the study but wrote an editorial accompanying the work3.

"[The results] might suggest that higher maternal education is associated with increased access to diagnoses and treatments for autism and ADHD, "she says," but we are not certain of the data reported in this paper. "

Health inequalities:

Some experts say they fear that people think the numbers reflect a real increase in prevalence.

Researchers are cautious in their interpretation, says David Mandell, director of Penn's Center for Mental Health at the University of Pennsylvania. "Unfortunately, what is captured, it's often the title and the abstract," he says. "My biggest concern with this survey is – and has always been – that it's not prevalence."

However, surveys like this one are important, Mandell said, because of what they reveal about disparities in children's access to services. "[They] can be an excellent tool to address the inequities in our society regarding the care we provide, "he said.

Systemic biases in the diagnosis of autism have already been reported4. Black and Hispanic children are more likely than white children not to have consistent health records and, as a result, to be excluded from prevalence estimates. And black children are half as likely as white children to be assessed for autism at age 3. The new survey is the first to incorporate data on the socio-economic status of families.

According to Santhosh Girirajan, associate professor of biochemistry and molecular biology at Pennsylvania State University, inconsistencies in children's access to health care may explain ethnic disparities in the prevalence of autism, which did not participate in works. "We very differently diagnose children belonging to specific ethnic groups".

Epidemiologists should use the skills of pediatricians, geneticists and other health care researchers to distinguish trends within autism subtypes, Girirajan said. "By looking at the prevalence without looking at the heterogeneity of the diagnosis, we are only seeing one dimension of what is happening."

Zablotsky says his team plans to regularly re-evaluate the survey questions to improve the quality of the survey and to ensure that they accurately capture the populations of the survey. ;interest.

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