1 in 110

by Benison O'Reilly on Tuesday, February 16th, 2010

At Christmas time I said I planned to write about the latest CDC (US Centers for Disease Control and Prevention) ASD prevalence data, released on December 18 last year. Finally I’ve got around to doing it.

There were some mutterings on the Internet that we would have confirmation of that 1 in 100 figure, which was reported in a couple of other studies last year, but the CDC prevalence—amongst 8-year olds in 2006—was subsequently revealed to be the slightly less newsworthy  1 in 110. Still, that’s a big increase from the previous survey conducted in 2002.

The full title of the study is: Prevalence of Autism Spectrum Disorders — Autism and Developmental Disabilities Monitoring Network, United States, 2006. MMWR 2009; 58(SS10):1-20

Prevalence was estimated through a retrospective review of records in eleven sites participating in the Autism and Developmental Disabilities Monitoring (ADDM) Network. To analyse changes in ASD prevalence, CDC compared the 2006 data with corresponding 2002 data, collected from 10 sites (all sites the same with the exception of Florida, which was not included in the 2002 survey). Children aged 8 years with a diagnosis of an ASD or descriptions consistent with an ASD were identified through screening and review of health and education records.

Overall 2,757 (0.9%) of 307,790 children aged 8 years were identified as having an ASD, indicating an overall average prevalence of 9.0 per 1,000 population. Thus in 2006, on average, approximately 1% or one child in every 110 was classified as having an ASD.

The average prevalence of ASDs among children aged 8 years increased 57% from 2002 to 2006.  The researchers believe that whilst some of the increases are due to better detection, a true increase in risk cannot be ruled out.

Delays in diagnosis persisted (average age at diagnosis was 54 months) but ASDs were diagnosed by professionals at earlier ages in 2006 than in 2002.  Forty-one percent of children with an ASD also had signs of intellectual disability, confirming what a lot of us already knew: the majority of people on the spectrum are not intellectually impaired, as originally believed.

If you’re interested, more information is available at:

www.cdc.gov/ncbddd/features/counting-autism.html

Tags: autism, prevalence, research