Autism epidemiology and demographics: Difference between revisions
No edit summary |
|||
| Line 45: | Line 45: | ||
A 2008 Hong Kong study reported an ASD incidence rate similar to those reported in Australia and North America, and lower than Europeans. It also reported a prevalence of 1.68 per 1,000 for children under 15 years.<ref>{{cite journal |journal= J Child Neurol |date=2008 |volume=23 |issue=1 |pages=67–72 |title= Epidemiological study of autism spectrum disorder in China |author= Wong VCN, Hui SLH |doi=10.1177/0883073807308702 |pmid=18160559}}</ref> | A 2008 Hong Kong study reported an ASD incidence rate similar to those reported in Australia and North America, and lower than Europeans. It also reported a prevalence of 1.68 per 1,000 for children under 15 years.<ref>{{cite journal |journal= J Child Neurol |date=2008 |volume=23 |issue=1 |pages=67–72 |title= Epidemiological study of autism spectrum disorder in China |author= Wong VCN, Hui SLH |doi=10.1177/0883073807308702 |pmid=18160559}}</ref> | ||
====Venezuela==== | ====Venezuela==== | ||
A 2008 study reported a prevalence of | A 2008 study reported a prevalence of 110 per 100,000 for autism and 170 per 100,000 for ASD.<ref>{{cite journal |journal=Autism |date=2008 |volume=12 |issue=2 |pages=191–202 |title= Epidemiological findings of pervasive developmental disorders in a Venezuelan study |author= Montiel-Nava C, Peña JA |doi=10.1177/1362361307086663 |pmid=18308767}}</ref> | ||
==References== | ==References== | ||
Revision as of 22:53, 10 February 2013
|
Autism Microchapters |
|
Diagnosis |
|---|
|
Treatment |
|
Case Studies |
|
Autism epidemiology and demographics On the Web |
|
American Roentgen Ray Society Images of Autism epidemiology and demographics |
|
Risk calculators and risk factors for Autism epidemiology and demographics |
Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]
Overview
Most recent reviews estimate a prevalence of 100- 200 cases per 100,000 people for autism, and about 600 per 100,000 for ASD, with ASD averaging a 4.3:1 male-to-female ratio. The number of people known to have autism has increased dramatically since the 1980s, at least partly due to changes in diagnostic practice; the question of whether actual prevalence has increased is unresolved.
Epidemiology and Demographics
Prevalence
Most recent reviews tend to estimate a prevalence of 100– 200 per 100,000 for autism and close to 600 per 100,000 for ASD;[1] because of inadequate data, these numbers may underestimate ASD's true prevalence.[2] PDD-NOS is the vast majority of ASD, Asperger's is about 30 per 100,000 and the remaining ASD forms are much rarer.[3] A 2006 study of nearly 57,000 British nine- and ten-year-olds reported a prevalence of 389 per 100,000 for autism and 1,161 per 100,000 for ASD; these higher figures could be associated with broadening diagnostic criteria.[4] Studies based on more-detailed information, such as direct observation rather than examination of medical records, identify higher prevalence; this suggests that published figures may underestimate ASD's true prevalence.[2]
Changes with Time
Attention has been focused on whether the prevalence of autism is increasing with time. Earlier prevalence estimates were lower, centering at about 50 per 100,000 for autism during the 1960s and 1970s and about 100 per 100,000 in the 1980s, as opposed to today's 100- 200 per 100,000.[1]
The number of reported cases of autism increased dramatically in the 1990s and early 2000s, prompting investigations into several potential reasons:[5]
- More children may have autism; that is, the true frequency of autism may have increased.
- There may be more complete pickup of autism (case finding), as a result of increased awareness and funding. For example, attempts to sue vaccine companies may have increased case-reporting.
- The diagnosis may be applied more broadly than before, as a result of the changing definition of the disorder, particularly changes in DSM-III-R and DSM-IV.
- Successively earlier diagnosis in each succeeding cohort of children, including recognition in nursery (preschool), may have affected apparent prevalence but not incidence.
The reported increase is largely attributable to changes in diagnostic practices, referral patterns, availability of services, age at diagnosis, and public awareness.[1][6][7] A widely cited 2002 pilot study concluded that the observed increase in autism in California cannot be explained by changes in diagnostic criteria,[8] but a 2006 analysis found that special education data poorly measured prevalence because so many cases were undiagnosed, and that the 1994–2003 U.S. increase was associated with declines in other diagnostic categories, indicating that diagnostic substitution had occurred.[9] A 2007 study that modeled autism incidence found that broadened diagnostic criteria, diagnosis at a younger age, and improved efficiency of case ascertainment, can produce an increase in the frequency of autism ranging up to 29-fold depending on the frequency measure, suggesting that methodological factors may explain the observed increases in autism over time.[10] A small 2008 study found that a significant number of people diagnosed with language impairments as children in previous decades would now be given a diagnosis as autism.[11]
Several contributing environmental risk factors have been proposed to support the hypothesis that the actual frequency of autism has increased. These include certain foods, infectious disease, pesticides, MMR vaccine, and vaccines containing the preservative thiomersal, formerly used in several childhood vaccines in the U.S.[1] Although there is overwhelming scientific evidence against the MMR hypothesis and no convincing evidence for the thiomersal hypothesis, other as-yet-unidentified contributing environmental risk factors cannot be ruled out.[6] Although it is unknown whether autism's frequency has increased, any such increase would suggest directing more attention and funding toward changing environmental factors instead of continuing to focus on genetics.[12]
Developed Countries
Australia
A 2008 Australian study reported wide variation and inconsistent results in prevalence estimates; for example, national estimates for the prevalence of ASD in Australia ranged from 1.21 to 3.57 per 1,000 for children aged 6–12 years. The study concluded that the prevalence of ASD in Australian children cannot be estimated accurately from existing data.[13]
Denmark
A 2003 study reported that the cumulative incidence of autism in Denmark began a steep increase starting around 1990, and continued to grow until 2000, despite the withdrawal of thiomersal-containing vaccines in 1992. For example, for children aged 2–4 years, the cumulative incidence was about 0.5 new cases per 10,000 children in 1990 and about 4.5 new cases per 10,000 children in 2000.[14]
Germany
A 2008 study found that inpatient admission rates for children with ASD increased 30% from 2000 to 2005, with the largest rise between 2000 and 2001 and a decline between 2001 and 2003. Inpatient rates for all mental disorders also rose for ages up to 15 years, so that the ratio of ASD to all admissions rose from 1.3% to 1.4%.[15]
Japan
A 2005 study of a part of Yokohama with a stable population of about 300,000 reported a cumulative incidence to age 7 years of 48 cases of ASD per 10,000 children in 1989, and 86 in 1990. After the vaccination rate of MMR vaccine dropped to near zero, the incidence rate grew to 97 and 161 cases per 10,000 children in 1993 and 1994, respectively, indicating that MMR vaccine did not cause autism.[16]
United Kingdom
The incidence and changes in incidence with time are unclear in the UK.[17] The reported autism incidence in the UK rose starting before the first introduction of the MMR vaccine in 1989.[18] A 2004 study found that the reported incidence of pervasive developmental disorders in a general practice research database in England and Wales grew steadily during 1988–2001 from 0.11 to 2.98 per 10,000 person-years, and concluded that much of this increase may be due to changes in diagnostic practice.[19]
United States
The number of diagnosed cases of autism grew dramatically in the U.S. in the 1990s and early 2000s. For example, in 1996, 21,669 children and students aged 6–11 years diagnosed with autism were served under Part B of the Individuals with Disabilities Education Act (IDEA) in the U.S. and outlying areas; by 2001 this number had risen to 64,094, and by 2005 to 110,529.[20] These numbers measure what is sometimes called "administrative prevalence", that is, the number of known cases per unit of population, as opposed to the true number of cases.[9]
A population-based study of one Minnesota county found that the cumulative incidence of autism grew eightfold from the 1980–83 period to the 1995–97 period. The increase occurred after the introduction of broader, more-precise diagnostic criteria, increased service availability, and increased awareness of autism.[21]
Developing Countries
China
A 2008 Hong Kong study reported an ASD incidence rate similar to those reported in Australia and North America, and lower than Europeans. It also reported a prevalence of 1.68 per 1,000 for children under 15 years.[22]
Venezuela
A 2008 study reported a prevalence of 110 per 100,000 for autism and 170 per 100,000 for ASD.[23]
References
- ↑ 1.0 1.1 1.2 1.3 Newschaffer CJ, Croen LA, Daniels J; et al. (2007). "The epidemiology of autism spectrum disorders". Annu Rev Public Health. 28: 235–58. doi:10.1146/annurev.publhealth.28.021406.144007. PMID 17367287.
- ↑ 2.0 2.1 Caronna EB, Milunsky JM, Tager-Flusberg H (2008). "Autism spectrum disorders: clinical and research frontiers". Arch Dis Child. 93 (6): 518–23. doi:10.1136/adc.2006.115337. PMID 18305076.
- ↑ Fombonne E (2005). "Epidemiology of autistic disorder and other pervasive developmental disorders". J Clin Psychiatry. 66 (Suppl 10): 3–8. PMID 16401144.
- ↑ Baird G, Simonoff E, Pickles A; et al. (2006). "Prevalence of disorders of the autism spectrum in a population cohort of children in South Thames: the Special Needs and Autism Project (SNAP)". Lancet. 368 (9531): 210–5. doi:10.1016/S0140-6736(06)69041-7. PMID 16844490.
- ↑ Wing L, Potter D (1999). "Notes on the prevalence of autism spectrum disorders". National Autistic Society. Retrieved 2007-12-10.
- ↑ 6.0 6.1 Rutter M (2005). "Incidence of autism spectrum disorders: changes over time and their meaning". Acta Paediatr. 94 (1): 2–15. PMID 15858952.
- ↑ Prevalence and changes in diagnostic practice:
- Fombonne E (2003). "The prevalence of autism". JAMA. 289 (1): 87–9. doi:10.1001/jama.289.1.87. PMID 12503982.
- Wing L, Potter D (2002). "The epidemiology of autistic spectrum disorders: is the prevalence rising?". Ment Retard Dev Disabil Res Rev. 8 (3): 151–61. doi:10.1002/mrdd.10029. PMID 12216059.
- ↑ Template:Cite paper
- ↑ 9.0 9.1 Shattuck PT (2006). "The contribution of diagnostic substitution to the growing administrative prevalence of autism in US special education". Pediatrics. 117 (4): 1028–37. doi:10.1542/peds.2005-1516. PMID 16585296. Lay summary (2006-04-03).
- ↑ Wazana A, Bresnahan M, Kline J (2007). "The autism epidemic: fact or artifact?". J Am Acad Child Adolesc Psychiatry. 46 (6): 721–30. doi:10.1097/chi.0b013e31804a7f3b. PMID 17513984.
- ↑ Bishop DVM, Whitehouse AJO, Watt HJ, Line EA (2008). "Autism and diagnostic substitution: evidence from a study of adults with a history of developmental language disorder". Dev Med Child Neurol. 50 (5): 341–5. doi:10.1111/j.1469-8749.2008.02057.x. PMID 18384386.
- ↑ Szpir M (2006). "Tracing the origins of autism: a spectrum of new studies". Environ Health Perspect. 114 (7): A412–8. PMID 16835042.
- ↑ Williams K, Macdermott S, Ridley G, Glasson EJ, Wray JA (2008). "The prevalence of autism in Australia. Can it be established from existing data?". J Paediatr Child Health. doi:10.1111/j.1440-1754.2008.01331.x. PMID 18564076.
- ↑ Madsen KM, Lauritsen MB, Pedersen CB; et al. (2003). "Thimerosal and the occurrence of autism: negative ecological evidence from Danish population-based data". Pediatrics. 112 (3): 604–6. doi:10.1542/peds.112.3.604. PMID 12949291.
- ↑ Bölte S, Poustka F, Holtmann M (2008). "Trends in autism spectrum disorder referrals". Epidemiology. 19 (3): 519–20. doi:10.1097/EDE.0b013e31816a9e13. PMID 18414094.
- ↑ Honda H, Shimizu Y, Rutter M (2005). "No effect of MMR withdrawal on the incidence of autism: a total population study". J Child Psychol Psychiatry. 46 (6): 572–9. doi:10.1111/j.1469-7610.2005.01425.x. PMID 15877763. Lay summary – Bandolier (2005).
- ↑ "Incidence of autism". National Autistic Society. 2004. Retrieved 2007-12-10.
- ↑ Kaye JA, del Mar Melero-Montes M, Jick H (2001). "Mumps, measles, and rubella vaccine and the incidence of autism recorded by general practitioners: a time trend analysis". BMJ. 322 (7284): 460–3. doi:10.1136/bmj.322.7284.460. PMID 11222420.
- ↑ Smeeth L, Cook C, Fombonne E; et al. (2004). "Rate of first recorded diagnosis of autism and other pervasive developmental disorders in United Kingdom general practice, 1988 to 2001". BMC Med. 2: 39. doi:10.1186/1741-7015-2-39. PMID 15535890.
- ↑ "Children and students served under IDEA, Part B, in the U.S. and outlying areas by age group, year and disability category: fall 1996 through fall 2005". U.S. Department of Education, Office of Special Education Programs. 2006. Retrieved 2007-10-03.
- ↑ Barbaresi WJ, Katusic SK, Colligan RC, Weaver AL, Jacobsen SJ (2005). "The incidence of autism in Olmsted County, Minnesota, 1976-1997: results from a population-based study". Arch Pediatr Adolesc Med. 159 (1): 37–44. doi:10.1001/archpedi.159.1.37. PMID 15630056.
- ↑ Wong VCN, Hui SLH (2008). "Epidemiological study of autism spectrum disorder in China". J Child Neurol. 23 (1): 67–72. doi:10.1177/0883073807308702. PMID 18160559.
- ↑ Montiel-Nava C, Peña JA (2008). "Epidemiological findings of pervasive developmental disorders in a Venezuelan study". Autism. 12 (2): 191–202. doi:10.1177/1362361307086663. PMID 18308767.