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Autism prevalence trends over time in Denmark: changes in prevalence and age at diagnosis.
Arch Pediatr Adolesc Med. 2008 Dec; 162(12):1150-6.AP

Abstract

OBJECTIVE

To examine the effect of changing age at diagnosis on the diagnosed prevalence of autism among different birth cohorts.

DESIGN

Population-based cohort study.

SETTING

Children were identified in the Danish Medical Birth Registry and psychiatric outcomes were obtained via linkage with the Danish National Psychiatric Register.

PARTICIPANTS

All children born in Denmark from January 1, 1994, through December 31, 1999 (N = 407 458).

MAIN OUTCOME MEASURES

The age-specific prevalence, hazard ratio, and relative risk by age.

RESULTS

Statistically significant shifts in age at diagnosis were observed for autism spectrum disorder; children diagnosed before age 9 years in the cohorts born between January 1, 1994, and December 31, 1995, between January 1, 1996, and December 31, 1997, and between January 1, 1998, and December 31, 1999, were on average diagnosed at ages 5.9 (95% confidence interval [CI], 5.8-6.0), 5.8 (95% CI, 5.7-5.9), and 5.3 (95% CI, 5.2-5.4) years, respectively. The relative risk comparing the 1996-1997 birth cohort with the 1994-1995 birth cohort at age 3 years was 1.20 (95% CI, 0.86-1.67), which decreased to 1.10 (95% CI, 1.00-1.20) at age 11 years. Similarly, the relative risk comparing the 1998-1999 birth cohort with the 1994-1995 birth cohort at age 3 years was 1.69 (95% CI, 1.24-2.31), which decreased to 1.23 (95% CI, 1.11-1.37) at age 11 years. Similar results were observed for childhood autism.

CONCLUSIONS

Shifts in age at diagnosis inflated the observed prevalence of autism in young children in the more recent cohorts compared with the oldest cohort. This study supports the argument that the apparent increase in autism in recent years is at least in part attributable to decreases in the age at diagnosis over time.

Authors+Show Affiliations

Department of Biostatistics, Institute of Public Health, University of Aarhus, Vennelyst Boulevard 6, DK-8000 Aarhus C, Denmark. parner@biostat.au.dkNo affiliation info availableNo affiliation info available

Pub Type(s)

Comparative Study
Journal Article

Language

eng

PubMed ID

19047542

Citation

Parner, Erik T., et al. "Autism Prevalence Trends Over Time in Denmark: Changes in Prevalence and Age at Diagnosis." Archives of Pediatrics & Adolescent Medicine, vol. 162, no. 12, 2008, pp. 1150-6.
Parner ET, Schendel DE, Thorsen P. Autism prevalence trends over time in Denmark: changes in prevalence and age at diagnosis. Arch Pediatr Adolesc Med. 2008;162(12):1150-6.
Parner, E. T., Schendel, D. E., & Thorsen, P. (2008). Autism prevalence trends over time in Denmark: changes in prevalence and age at diagnosis. Archives of Pediatrics & Adolescent Medicine, 162(12), 1150-6. https://doi.org/10.1001/archpedi.162.12.1150
Parner ET, Schendel DE, Thorsen P. Autism Prevalence Trends Over Time in Denmark: Changes in Prevalence and Age at Diagnosis. Arch Pediatr Adolesc Med. 2008;162(12):1150-6. PubMed PMID: 19047542.
* Article titles in AMA citation format should be in sentence-case
TY - JOUR T1 - Autism prevalence trends over time in Denmark: changes in prevalence and age at diagnosis. AU - Parner,Erik T, AU - Schendel,Diana E, AU - Thorsen,Poul, PY - 2008/12/3/pubmed PY - 2008/12/19/medline PY - 2008/12/3/entrez SP - 1150 EP - 6 JF - Archives of pediatrics & adolescent medicine JO - Arch Pediatr Adolesc Med VL - 162 IS - 12 N2 - OBJECTIVE: To examine the effect of changing age at diagnosis on the diagnosed prevalence of autism among different birth cohorts. DESIGN: Population-based cohort study. SETTING: Children were identified in the Danish Medical Birth Registry and psychiatric outcomes were obtained via linkage with the Danish National Psychiatric Register. PARTICIPANTS: All children born in Denmark from January 1, 1994, through December 31, 1999 (N = 407 458). MAIN OUTCOME MEASURES: The age-specific prevalence, hazard ratio, and relative risk by age. RESULTS: Statistically significant shifts in age at diagnosis were observed for autism spectrum disorder; children diagnosed before age 9 years in the cohorts born between January 1, 1994, and December 31, 1995, between January 1, 1996, and December 31, 1997, and between January 1, 1998, and December 31, 1999, were on average diagnosed at ages 5.9 (95% confidence interval [CI], 5.8-6.0), 5.8 (95% CI, 5.7-5.9), and 5.3 (95% CI, 5.2-5.4) years, respectively. The relative risk comparing the 1996-1997 birth cohort with the 1994-1995 birth cohort at age 3 years was 1.20 (95% CI, 0.86-1.67), which decreased to 1.10 (95% CI, 1.00-1.20) at age 11 years. Similarly, the relative risk comparing the 1998-1999 birth cohort with the 1994-1995 birth cohort at age 3 years was 1.69 (95% CI, 1.24-2.31), which decreased to 1.23 (95% CI, 1.11-1.37) at age 11 years. Similar results were observed for childhood autism. CONCLUSIONS: Shifts in age at diagnosis inflated the observed prevalence of autism in young children in the more recent cohorts compared with the oldest cohort. This study supports the argument that the apparent increase in autism in recent years is at least in part attributable to decreases in the age at diagnosis over time. SN - 1538-3628 UR - https://www.unboundmedicine.com/medline/citation/19047542/Autism_prevalence_trends_over_time_in_Denmark:_changes_in_prevalence_and_age_at_diagnosis_ L2 - https://jamanetwork.com/journals/jamapediatrics/fullarticle/10.1001/archpedi.162.12.1150 DB - PRIME DP - Unbound Medicine ER -