Journal of Autism and Developmental Disorders

, Volume 39, Issue 3, pp 464–470

The Incidence of Clinically Diagnosed Versus Research-Identified Autism in Olmsted County, Minnesota, 1976–1997: Results from a Retrospective, Population-Based Study

  • William J. Barbaresi
  • Robert C. Colligan
  • Amy L. Weaver
  • Slavica K. Katusic
Original Paper

DOI: 10.1007/s10803-008-0645-8

Cite this article as:
Barbaresi, W.J., Colligan, R.C., Weaver, A.L. et al. J Autism Dev Disord (2009) 39: 464. doi:10.1007/s10803-008-0645-8


Autism prevalence studies have often relied on administrative prevalence or clinical diagnosis as case-identification strategies. We report the incidence of clinical diagnoses of autism spectrum disorders (ASD), versus research-identified autism among residents of Olmsted County, Minnesota, age ≤21 years, from 1976–1997. The incidence of clinically diagnosed ASD (with 95% CI) was 1.5 per 100,000 (0.0–3.7) in 1980–1983 and 33.1 (22.8–43.3) in 1995–1997, a 22.1-fold increase. In contrast, the incidence of research-identified autism increased from 5.5 (1.4–9.5) per 100,000 to 44.9 (32.9–56.9), an 8.2-fold increase. Only 46.8% of research-identified cases received a clinical diagnosis of ASD. These findings demonstrate the potential for misleading interpretation of results from epidemiologic studies that rely on clinical diagnosis of autism to identify cases.


Autism Epidemiology Autistic disorder Incidence Population-based 

Copyright information

© Springer Science+Business Media, LLC 2008

Authors and Affiliations

  • William J. Barbaresi
    • 1
    • 2
  • Robert C. Colligan
    • 3
  • Amy L. Weaver
    • 4
  • Slavica K. Katusic
    • 2
    • 5
  1. 1.Department of Pediatric and Adolescent Medicine, Division of Developmental and Behavioral PediatricsCollege of Medicine, Mayo ClinicRochesterUSA
  2. 2.Mayo Clinic Dana Child Development and Learning Disorders ProgramCollege of Medicine, Mayo ClinicRochesterUSA
  3. 3.Department of Psychiatry and PsychologyCollege of Medicine, Mayo ClinicRochesterUSA
  4. 4.Department of Health Sciences Research, Division of BiostatisticsCollege of Medicine, Mayo ClinicRochesterUSA
  5. 5.Department of Health Sciences Research, Division of EpidemiologyCollege of Medicine, Mayo ClinicRochesterUSA

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