The prevalence of autism spectrum disorder (ASD) in 8-year-old children in 2012 was estimated to be 14.6 per 1,000, or one in 68, according to the Centers for Disease Control and Prevention.
The estimate, published online March 31 in CDC’s Morbidity and Mortality Weekly Report ( Surveill Summ. 2016. Apr 1;65:1-23 ) is similar to that seen in CDC’s 2010 survey of 8-year-old children, where 14.7 of 1,000 were estimated affected. In CDC surveys prior to 2010, prevalence was usually seen increasing over time, from 6.6 children per 1,000 in 2002 to 9 in 2006 and 11.3 in 2008.
However, the investigators led by Deborah L. Christensen, Ph.D., of the CDC’s National Center on Birth Defects and Disabilities, Atlanta, cautioned that it was premature to conclude that overall prevalence of ASD was stabilizing, in part because of significant variation seen among the 11 study sites and because of potential underevaluation or delayed evaluation among some ethnic and racial subgroups. Also, prevalence was significantly higher at surveillance sites where both education and health records were reviewed (17.1 per 1,000), compared with sites where investigators reviewed health records only (10.7 per 1,000).
The CDC’s Autism and Developmental Disabilities Monitoring Network screens children in 11 states (Arkansas, Arizona, Colorado, Georgia, Maryland, Missouri, New Jersey, North Carolina, South Carolina, Utah, and Wisconsin) using health care and education sources to determine rates of ASD. The network surveillance area covered about 350,000 8-year-old children (53% white, 21% black, 20% Hispanic, 5% Asian, and 1% American Indian/Alaska Native) in 2012. Prevalence was markedly higher among boys (23.6 per 1,000, or 1 in 42) than among girls (5.3 per 1,000, or 1 in 189), a difference largely unchanged from previous studies.
ASD prevalence by ethnic or racial subgroup also did not change significantly over prior surveys, the investigators reported. However, lower estimates among black and Hispanic children could reflect “differences in awareness of ASD or access to specialty diagnostic services,” they wrote. Fewer black and Hispanic children in the survey had a comprehensive developmental evaluation by age 36 months (40% and 39%, respectively), compared with non-Hispanic white children (45%), which investigators called worrisome, as “early treatment might maximize the ability of children to function and participate in their community.”
Moreover, prevalence was seen increasing significantly over the previous survey in two states (New Jersey and Wisconsin), and decreasing significantly in one state (Missouri). Investigators suspected that variation in local health care systems’ ability to obtain comprehensive developmental evaluations might be a factor.
The wide range of ASD prevalence estimates, the investigators wrote, demands “caution in interpreting the similarity of overall estimated ASD prevalence between 2010 and 2012.”
The CDC funded the study and investigators disclosed no conflicts of interest.