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Research Letter
November 6, 2018

Cumulative Incidence of Autism Into Adulthood for Birth Cohorts in Denmark, 1980-2012

Author Affiliations
  • 1Lundbeck Foundation Initiative for Integrative Psychiatric Research (iPSYCH), Aarhus University, Aarhus, Denmark
JAMA. 2018;320(17):1811-1813. doi:10.1001/jama.2018.11328

The Centers for Disease Control and Prevention recently reported an autism prevalence of 1.68% among 8-year-old children in the United States in 2014,1 which is 14% higher than the reported rate for 8-year-old children in 2012 and 2010.2,3 Autism prevalence rates of 2% and 2.47% in school-aged children were previously estimated from parent report data in US national health surveys.4,5 These cross-sectional data may suggest that autism spectrum disorder (ASD) prevalence is reaching a peak. However, longitudinal data with follow-up into adulthood are needed to truly determine whether the prevalence has stabilized.

All live births in Denmark between 1980 and 2012 were identified in the Central Person Register and followed through 2016 for an ASD diagnosis (International Classification of Diseases, Eighth Revision codes 299.00, 299.01, 299.02, and 299.03; International Statistical Classification of Diseases and Related Health Problems, Tenth Revision codes F84.0, F84.1, F84.5, F84.8, and F84.9) via linkage with the Psychiatric Central Research and National Patient Registers containing diagnoses recorded by medical specialists (only inpatient contacts before 1995). Persons with suspected ASD receive a multidisciplinary evaluation at a psychiatric department and the final diagnosis is reported by a psychiatrist who has received mandatory registry-reporting training. Persons receiving the ASD subdiagnosis of pervasive development disorder, unspecified (International Statistical Classification of Diseases and Related Health Problems, Tenth Revision code F84.9) may be advised to return for re-evaluation.