The U.S. Centers for Disease Control and Prevention (CDC) recently published the first U.S. study of the prevalence of autism spectrum disorder (ASD) among adults. What are the findings of the CDC study, and what are the implications for digital accessibility for people with autism?
What the CDC Study Tells Us About Autism in the U.S.
The new CDC study, which was published May 10 in the Journal of Autism and Developmental Disorders, estimates that autism affects roughly 5.4 million people in the U.S. aged 18 and older. This would be a prevalence of 2.21 percent of U.S. adults, or roughly 1 in 45.
The study’s authors note that the U.S. lacks large-scale federal or state surveillance systems to monitor the prevalence of autism. To arrive at an estimate, the authors used existing data about the prevalence of autism in the U.S., applying a statistical technique known as Bayesian hierarchical modeling. The estimates were adjusted to account for mortality rates, as well as for the differing diagnosis rates between males and females.
Autism by region
The CDC study finds that the prevalence of autism is fairly consistent between U.S. states. Not surprisingly, states with large populations such as California, Texas, New York, and Florida are also home to the largest numbers of adults with autism.
Louisiana is the state with the lowest estimate of adults with autism (1.97 percent), while Massachusetts has the highest estimated rate (2.42 percent). The authors speculate that the difference is likely due to the availability of screening and diagnostic services, rather than any true geographic variation.
Autism by gender
Males are more frequently diagnosed with autism than females, although the reasons for this discrepancy are not fully known. Researchers have speculated a variety of causes, including both innate genetic factors and females being underdiagnosed.
The CDC’s new study estimates that 3.62 percent of men in the U.S. have ASD, compared with 0.86 percent of women. Male prevalence rates ranged from 3.17 percent in South Dakota to 4.01 percent in Massachusetts. Female prevalence rates ranged from 0.72 percent in Arkansas to 0.97 percent in Virginia.
Autism by age
The study’s estimate of a 2.21 percent autism rate among U.S. adults is slightly higher than previous work focusing on children. In March, the CDC estimated that 1.85 percent of U.S. children, or 1 in 54, are on the autism spectrum. Another study conducted in 2014 found an autism prevalence rate of 1.68 percent among 8-year-old children in 11 states.
The authors propose that this discrepancy is due to persistent underdiagnosis of children with autism, which leads to underestimates. As people age, doctors may be able to catch ASD cases that went undetected during childhood. The authors discount environmental factors as a possible explanation for the discrepancy, since previous studies have shown them to have a very minor impact.
Digital Accessibility for People with Autism
The CDC’s new study will help different states, and the U.S. as a whole, assess the need for services and support for people with autism, including in education, healthcare, and employment. One way to help the millions of U.S. adults with ASD is to work to improve web accessibility for people with autism.
People on the autism spectrum experience many possible symptoms, as well as a wide range of the severity of those symptoms. The suggestions below are a broad range of web accessibility best practices that may be relevant for some people with autism.
- Many people with autism strongly prefer routines and predictability. Having a consistent website navigation and layout will help avoid confusion and challenges for users with autism.
- Your website’s design and interface should be simple and clear, free from clutter and distractions that may overwhelm users. Content that moves, blinks, flashes, and/or automatically updates should also be avoided whenever possible, since many people with autism have sensory hypersensitivity.
- Visual supports (PDF) are often used to help people with autism communicate and learn information. Including images and graphics that help with comprehension can make your website more accessible to people with autism. However, be sure to have a text-based equivalent for all visual content for the use of people with visual disabilities.