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Autism diagnoses in the US rise by 30%, CDC reports

BMJ 2014; 348 doi: https://doi.org/10.1136/bmj.g2520 (Published 02 April 2014) Cite this as: BMJ 2014;348:g2520
  1. Michael McCarthy
  1. 1Seattle

One in every 68 US children has been identified as having autism spectrum disorder (ASD), says a new report from the US Centers for Disease Control and Prevention (CDC)—a 30% increase from the 1 in 88 prevalence reported by the agency in 2012.1

Marshalyn Yeargin-Allsop, chief of the CDC’s Developmental Disabilities branch, said that the reasons for the increase were unclear but that changes in prevalence may partly reflect improved recognition that autism is a spectrum of disorders, leading to its diagnosis in more children with higher IQs and in those who may be less severely affected.

The new report summarized data from 2010 collected by the CDC’s Autism and Developmental Disabilities Monitoring Network, an active surveillance system that tracks ASD trends in communities across 14 states.

The prevalence estimates were based on a review of records from a variety of sources including health providers, therapists, and schools.

The diagnosis of ASD was based on criteria from the Diagnostic and Statistical Manual of Mental Disorders, fourth edition, revised (DSM-IV-TR), which was published in 2000. The network has not changed its criteria for the diagnosis of ASD since its launch in 2000, and its surveillance methods have remained “as consistent as possible over time,” the report said.

The new study included data from 11 states: Alabama, Arizona, Arkansas, Colorado, Georgia, Maryland, Missouri, New Jersey, North Carolina, Utah, and Wisconsin.

It found that 1 in 68 (14.7 per 1000 eight year olds) had been identified in these communities with ASD, up from 1 in 88 (11.3 per 1000) in 2008, as reported by the CDC in 2012. Eight year olds were chosen because this is the age at which the diagnosis of autism peaks. The median age for diagnosis was 53 months.

Prevalence was highest in New Jersey, at 21.9 per 1000, and lowest in Alabama, at 5.7 per 1000.

The diagnosis of ASD was five times higher among boys than girls: 1 in 42 (23.7 per 1000) compared with 1 in 189 (5.3 per 1000).

Prevalence among white children (15.8 per 1000) was significantly greater than among black (12.3 per 1000) and Hispanic children (10.8 per 1000).

Nearly half (46%) of the children with ASD had average to above average intelligence with IQ scores greater than 85; 31% were classified as intellectually disabled (IQ of 70 or lower); and 23% were in the borderline range (IQ of 71-85).

The proportion of children with ASD who were classified as intellectually disabled varied considerably by race: about 48% of black children were classified as intellectually disabled, compared with 38% of Hispanic children and 25% of white children.

“Among white children, the prevalence of ASD without intellectual disability was nearly double the prevalence among either black children or Hispanic children (OR [odds ratio] = 1.8, p<0.01 for both comparisons),” the report said.

The most notable change over the past decade, the report said, was the growing proportion of children identified as having ASD who had average or above average intellectual ability, which had grown from 32% in 2002 to 38% in 2006, and to 46% in 2010.

The extent to which the variations in prevalence may be attributable to “diagnostic practices, under-recognition of ASD symptoms in some racial/ethnic groups, socioeconomic disparities in access to services, and regional differences in clinical or school based practices that might influence the findings in this report is unclear,” the researchers said.

The CDC researchers concluded that the findings indicated a need for standardized measures to document ASD symptoms and severity; efforts to improve the recognition of symptoms, particularly in those without intellectual disability and in all racial and ethnic groups; and initiatives to decrease the age of diagnosis so that affected children could be enrolled earlier in community based support symptoms.

Notes

Cite this as: BMJ 2014;348:g2520

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