Clarifying Startling Autism Rate Statistics

In March 2012, Time magazine writer Alice Park summarized the skyrocketing rates of autism in an article titled “Autism Rises”: “One in 88 children in the U.S. has an autism spectrum disorder (ASD) – a nearly 25 percent increase from 2006, when the rate was 1 in 110, and a stunning 78 percent increase since 2000-02, when the CDC first began tracking the disorder and estimated the rate at 1 in 150 children.”

Two years later, in March of this year, the Centers for Disease Control and Prevention announced a revised number. This time, the prevalence of autism was reported to be 1 in 68 children in the United States. It’s worth noting how and when these numbers were derived and the startling statistics that can be mined in the data disaggregation, particularly as it relates to gender and geographic differences in autism.

The CDC funds the Autism and Developmental Disabilities Monitoring Network, an organization designed to monitor the rate of autism and the resulting community impact. In 2010, the ADDM sites were situated in 11 states: Alabama, Arizona, Arkansas, Colorado, Georgia, Maryland, Missouri, New Jersey, North Carolina, Utah and Wisconsin. Often, only specific counties are used within the states, not the entire state itself. By analyzing the health and education records of 8-year-old children with autism in 2010 within the selected sites, the ADDM calculated the percentage of autism. As described by the CDC, “A total population of 363,749 children aged 8 years was covered by the 11 ADDM sites that provided data for the 2010 surveillance year. This number represented 9 percent of the total U.S. population of children aged 8 years in 2010.”

Given that the majority of children with autism are not formally diagnosed until age 4, the ADDM elected to base the population study on 8-year-old children to ensure a more complete picture of diagnosis.

Mathematically, prevalence, unlike incidence, does not indicate how many new cases will develop in a given year. Incidence is a frequency indicator. The statistic 1 in 68 is not indicative of new cases every year in the United States. It is a prevalence record, a snapshot of current cases of autism among 8-year-old children in 2010, and by the CDC’s own admission, it should not be generalized to the entire United States. The ADDM is currently in its next phase of survey using 12 different sites from educational and medical records collected in 2012.

The prevalence rates among the 11 sites varied significantly. The rate of autism is significantly greater for boys. In every site, the number of boys with autism exceeded girls by almost 5-to-1. As reported by the ADDM network, “1 in 42 boys and 1 in 189 girls living in the ADDM Network communities” have autism. Geographically, differences in prevalence vary greatly as well. In Denver, Colo., the prevalence of boys with autism was 1 in 50 and for girls it was 1 in 345. In Newark, N.J., the incidence jumps to 1 in 29 boys and 1 in 172 girls.

In terms of racial distribution, autism is more prevalent in Caucasian children. As reported by the CDC, “when data from all sites were combined, the estimated prevalence among white children (15.8 per 1,000) was significantly greater than that among black (12.3 per 1,000) and Hispanic children (10.8 per 1,000).”

The ADDM used the definition of autism from the fourth version of the Diagnostic and Statistical Manual, given the research was conducted prior to the adoption and dissemination of the most recent version of the manual. In May 2013, the American Psychological Association formally adopted the DSM-V revisions.

The fifth edition significantly changed the diagnostic criteria and labeling of autism. Autistic syndrome and Asperger syndrome were two of five different labels under the broader diagnostic category of pervasive developmental delay. In the revised version, autism is now classified as autism spectrum disorder with varying levels of severity (level 1 to 3). The label of Asperger syndrome was eliminated, although those currently who have the diagnosis will retain it.

While theories abound to explain the increase in the prevalence of autism, from greater awareness and understanding to more sophisticated diagnostic protocols, continual research is being conducted on other environmental factors that may serve as a trigger to autism. As reported in the Environmental Health Perspectives journal last month, researchers at the University of California-Davis demonstrated a correlation between rates of autism and three classes of pesticides. A review of the medical records of 970 participants revealed that nearly two-thirds of children ages 2-5 whose mothers, when pregnant, lived within one mile of an area treated with pesticides were now diagnosed with autism or developmental delay. The treated areas included farms, golf courses and recreational parks. Other research has also linked environmental air pollutants with an increased risk of autism.

Dr. Keely Camden is the dean of the College of Education at West Liberty University and an associate professor of education. She is a former special education teacher.