New research from the Centers for Disease Control and Prevention provides a more detailed look at how common intellectual disabilities are among children in this country. (iStock)
Researchers from the Centers for Disease Control and Prevention are offering a new estimate of the number of American children with intellectual disabilities.
In a study of 8-year-olds in multiple communities across the country, CDC researchers found that 1.2% had IQ scores of 70 or less to qualify for a diagnosis of intellectual disability.
The findings, published in the Disability Health Journal late last year, are based on data collected through the CDC’s Autism and Developmental Disorder Monitoring Network, which regularly reviews health and education records for 8-year-olds in select communities. The CDC uses the same methods to determine its autism prevalence estimates, which are usually updated every two years.
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For the 2014 study, researchers looked at records for over 215,000 children in nine states and identified children as mentally retarded if they had an IQ score of 70 or less or if they had a written statement from a qualified professional that the child’s intellectual was functioning fell into this area.
The vast majority of the children identified – 78% – had mild intellectual disabilities, while 12% were classified in the moderate category and 1% were classified as severe or severe. The researchers did not have exact IQ scores for the remaining children and could not indicate the severity.
Intellectual disability was about twice as common in boys as in girls and in black children compared to white children. The prevalence also varied dramatically by location, with Arkansas at the high end having twice as many cases as Minnesota and Tennessee, which reported the lowest rates.
Of the children with intellectual disabilities, the study found that 39% also had autism.
Although most cases of intellectual disability can be reliably diagnosed before age 5, the researchers found that almost a quarter of the children studied did not have an IQ test until they were 6 years old.
The researchers said their results are largely in line with previous estimates of the prevalence of intellectual disability based on surveys, administrative records, or data from individual states, but these previous studies lacked details on subpopulations.
The study’s authors stated that given the “significant differences” between racial, ethnic and socio-economic groups, the “results could serve to develop strategies to improve early access to intervention services to improve the quality of life of ID card children”.
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