Autism spectrum disorder

Autism spectrum disorder (ASD) is a developmental disability that can cause significant social, communication and behavioral challenges. There is often nothing about how people with ASD look that sets them apart from other people, but people with ASD may communicate, interact, behave, and learn in ways that are different from most other people. The learning, thinking, and problem-solving abilities of people with ASD can range from gifted to severely challenged. Some people with ASD need a lot of help in their daily lives; others need less.

A diagnosis of ASD now includes several conditions that used to be diagnosed separately: autistic disorder, pervasive developmental disorder not otherwise specified (PDD-NOS), and Asperger syndrome. These conditions are now all called autism spectrum disorder.

Confidence interval

A confidence interval gives an estimated range of values which is likely to include the information (e.g., prevalence) that we want to know about.  The interval is a range of values that you can have confidence contains the true value in the population. There are different levels of confidence intervals; the most common is 95%. With a 95% confidence interval, we say that we are 95% confident that the value in our population will be included in our interval.  5% of the time, it will not.  So, we could say, “We are 95% confident that the prevalence of ASD in 8-year-olds in our surveillance area was between 21 and 27 per 1,000 children in 2016.” Larger samples typically have smaller confidence intervals.  Smaller samples usually have bigger confidence intervals.

Developmental delay

A developmental delay is a persistent delay experienced by a child in reaching one or more developmental milestones—how children grow, move, communicate, interact, learn, and play.

Developmental disabilities

Developmental disabilities are a group of conditions due to an impairment in physical, learning, language, or behavior areas. These conditions begin during the developmental period, may impact day-to-day functioning, and usually last throughout a person’s lifetime.

Intellectual disability

Intellectual disability means that a person has difficulty learning at an expected level and functioning in daily life. In this report, intellectual disability is measured by intellectual quotient (IQ) test scores of less than or equal to 70. 


Prevalence is a scientific term that describes the number of people with a disease or condition among a defined group at a specific period in time. Prevalence is usually expressed as a percentage or proportion of the defined group. For this project, we counted the number of 8-year-olds in 2016 who were identified with ASD and then divided that number by the total number of 8-year-olds in our surveillance area during 2016.