Autism Prevalence Studies Data Table

Note: blank cells indicate data not available.

Title—publication title

Year published—publication year

Country—country where the study was conducted

Area(s)—the city or specific geographical area(s) where the study was conducted

Age range (years)—age range (in years) of the population studied

Study years—the study period (in years)

Case identification method—study source record(s)* used to identify individuals with autism (registry; health records; education records; survey [specify type: in-person, phone, mail, online]; service provider records; other [define]) *more than one method may be used

Case criterion—criteria* used to identify individuals with autism (DSM [specify edition]; ICD [specify version]; Rutter(1); Kanner(2); clinical impression; autism test [specify test]; special education classification; self-report; parental report; receipt of autism-specific services; other [define]) *more than one case criterion may be used

1. Rutter M. Diagnosis and definition of childhood autism. Journal of Autism and Childhood Schizophrenia. 1978;8(2):139-161.
2. Kanner L. Autistic disturbances of affective contact. Nervous Child. 1943;2:217-250.

Sample size—study population size (prevalence denominator)

Number of cases—individuals with autism (prevalence numerator)

Autism prevalence estimate—autism prevalence estimate per 1,000 population; autism prevalence estimates were reported or calculated by CDC under the following conditions. Autism prevalence was reported separately for multiple study years with no overall estimate (data from the most recent study year was reported to highlight the most up-to-date data); autism prevalence for multiple age ranges was reported separately with no overall estimate (the age range with the largest sample size or best quality data, as reported by study authors, was used); autism prevalence for multiple birth cohorts of data was reported separately with no overall estimate (the most recent birth cohort to date was used to highlight the most-up-to-date data); autism prevalence was reported separately by subtype of autism or separately by geographic area with no overall estimate (number of individuals with autism in each subgroup combined or combined geographic areas were used to estimate autism prevalence if possible. If not possible [for example, denominator for subgroup was not available], the estimate with the best quality data, as indicated by the author, was reported)

Confidence interval (CI)—95% confidence interval (CI) for the autism prevalence estimate; if a CI was not reported in the study, a CI was calculated using the Wilson method with this online tool: http://www.hutchon.net/Wilsons.htm

Male:female ratio—male to female ratio of individuals with autism

Non-Hispanic White:Hispanic prevalence ratio—non-Hispanic White to Hispanic ethnicity autism prevalence ratio

White:Black prevalence ratio—White to Black race autism prevalence ratio

Diagnosis age range (months)—age range (in months) of cases at time of autism diagnosis

Diagnosis mean age (months)—mean age (in months) of cases at time of autism diagnosis

Diagnosis median age (months)—median age (in months) of cases at time of autism diagnosis

IQ <70 (%)—percentage of individuals with autism with an IQ (intelligence quotient) less than 70

Adaptive score <70 (%)—percentage of individuals with autism with an adaptive score less than 70

Non-verbal or minimally verbal (%)—percentage of individuals with autism that are non-verbal or minimally verbal

Percentage of individual co-occurring conditions (%)—percentage of co-occurring conditions reported in individuals with autism (attention deficit disorder [ADD] or attention deficit hyperactivity disorder [ADHD]; anxiety; cerebral palsy [CP]; congenital rubella; depression; Down syndrome; encephalopathy; epilepsy/seizure disorder; fetal alcohol syndrome; fragile X; language delay; learning disability; mood disorder; neonatal abstinence syndrome; obsessive compulsive disorder [OCD]; oppositional defiant disorder [ODD]; prematurity; Rett syndrome*; sudden infant death syndrome [SIDS]; sickle cell disease [SCD]; Tourette syndrome; tuberous sclerosis) *For cases of Rett syndrome: if Rett syndrome cases were included in the autism prevalence estimate, Rett syndrome was not included as a co-occurring condition. If authors separated Rett syndrome from the autism prevalence estimate, it was included as a co-occurring condition and excluded from the prevalence estimate.

Autism types included—subtypes of autism included in the study as reported by the authors (early or classic infantile autism, autistic syndrome, autistic mental retardation, childhood autism, autistic-like conditions, pervasive developmental disorder [PDD], pervasive developmental disorder–not otherwise specified [PDD-NOS], autistic disorder, atypical autism, Asperger's syndrome, childhood disintegrative disorder [CDD], autism spectrum disorder [ASD])

Publication link—link to publication

CDC calculated values—indicates values calculated by CDC's abstractor (e.g., converting age range from months to years, calculating confidence interval [CI], calculating overall autism prevalence estimate when prevalence was reported separately for autism subtype or for geographic study area; calculating percentages of individuals with autism by IQ categories or with co-occurring conditions when only individual case numbers are reported)