The prevalence of parent-reported autism spectrum disorders among children significantly increased from 2007, according to a report co-written by the CDC and the Health Resources and Services Administration. The increase of autism spectrum disorder diagnoses was greatest among boys and adolescents aged 14 to 17 years.
The increase continued through 2011-2012, the result of diagnoses of children with previously unrecognized ASD, according to the researchers.
The data for the report was collected by the CDC from the National Survey of Children’s Health, a nationally representative telephone survey of households with school-aged children.
Parent-reported ASD among children aged 6 to 17 years was 2% in 2011-2012 vs. 1.16% in 2007. Significant increases were observed for all age groups (1.31% to 1.82% for children aged 6 to 9 years; 1.45% to 2.39% for children aged 10 to 13 years; and 0.73% to 1.78% for adolescents aged 14 to 17 years).
The rise in ASD was especially pronounced among boys, increasing from 1.8% to 3.23%. The increase among girls was not statistically significant.
ASD diagnoses in 2008 or after accounted for the bulk of the increase in ASD prevalence, according to the researchers. For example, children diagnosed in 2008 or after represented 50% of those with a parent-reported ASD who were aged 6 to 9 years.
Children aged 6 to 17 years diagnosed in 2008 or after also were more likely to have a milder ASD than those diagnosed before 2007 (58.3% vs. 49.5%) and were less likely to have a severe ASD (6.9% vs. 16.9%).
“Together, these findings suggest that the increase in prevalence of parent-reported ASD may have resulted from improved ascertainment of ASD by doctors and other health care professionals in recent years, especially when the symptoms are mild,” the researchers wrote.