A new study in the Journal of Developmental and Behavioral Pediatrics provides a first look at the prevalence of autism spectrum disorder (ASD) among 4-year-olds. Researchers studied health and educational records for ASD indicators from a subset of the sites participating in the 2010 Autism and Developmental Disabilities Monitoring Network – a network connected with the Centers for Disease Control (CDC).
The key finding shows that prevalence among 4-year-olds was 30 percent lower than CDC estimates for 8-year-olds. The sample used in the new study involved children who turned 4 in 2010, while current CDC prevalence numbers are based on children who turned 8 in 2010. This new data does not replace the CDC prevalence estimate of 1 in 68 at age 8, but it does provide new insight into early diagnosis.
Autism Speaks Director of Public Health Research Michael Rosanoff said, “The difference in prevalence is likely explained by the fact that some 4-year-old children with autism were missed by these study methods.”
The study utilized record-review surveillance methods, which are very similar to the methods the CDC used in its previous research on 8-year-olds. Rosanoff said the methodology could have also contributed to the variation adding, “Less severely affected children were more likely to be missed at 4 years of age than at 8 years of age. These findings may not account for 4-year-olds who may have been diagnosed at a later age.”
The study also examined age of first diagnosis and found that 4-year-olds received their diagnosis an average of three months earlier than the 8-year-olds previously studied.
Rosanoff said, “While autism in many cases can be reliably diagnosed as early as 2-years-old, the average age of diagnosis in the U.S. still remains greater than 4.”
Dr. Paul Wang, Autism Speaks senior vice president and head of medical research, said the findings offer some good news. “The data suggest we are making progress in bringing down the age of diagnosis, but there are still many children who are not diagnosed at age 4, when we want to start appropriate interventions earlier than that. We need to continue to work to bring down that age.”
Dr. Wang added, “It's also clear that when there are concerns, a comprehensive evaluation is critical, and in too many communities, the medical system is not up to the task.”