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Encyclopedia > Autism (incidence)

The reported incidence of autism varies considerably among countries and is complicated by varying criteria for diagnosing autism, different standards for reporting public health problems, and other possible variations.


Many of the most well-funded public health systems in the world note a significant increase[citation needed] in the incidence of autism. The incidence of disease is defined as the number of new cases of disease occurring in a population during a defined time interval. ...

Contents

Background

Autism was first characterised in 1943 by psychiatrist Dr. Leo Kanner of the Johns Hopkins Hospital in Baltimore, and almost simultaneously, in German, by Dr Hans Asperger. Both published case series of children with strikingly similar features. Dr Leo Kanner MD Leo Kanner (June 13, 1894 - April 4, 1981) was an Austrian-American physician known for his work related to autism. ... The Johns Hopkins Hospital is a teaching hospital in Baltimore, Maryland. ... Hans Asperger, who discovered Asperger syndrome, described his patients as little professors. Hans Asperger (b. ...


The number of children born in each year diagnosed with autism in countries reporting figures is larger now than then. The populations of those countries have also increased but it is unclear what change in the incidence fraction has occurred. Public health organizations and researchers are not yet confident they have completely determined causes for all changes in the rate of reports of Autism (vide infra). Potential factors listed by the UK National Autistic Society include:[1] Incidence is the number of new cases of a disease during a given time interval, usually one year. ...

  • The underlying condition may have a changing incidence with time, i.e., more children (and/or more per thousand born) are affected by it;
  • More complete pickup of autism (case finding), as a result of increased awareness and funding;
  • Attempts in the US and UK to sue vaccine companies may have also increased case-reporting.[2]
  • The diagnosis being applied more broadly than before, as a result of the changing definition of the disorder, particularly changes in DSM-III-R;[3] and DSM-IV [4]
  • Successively earlier diagnosis in each succeeding cohort of children including recognition in nursery (preschool) - this would affect apparent prevalence but not incidence

Incidence

The incidence of a condition is the rate at which new cases occur in a population during a specified interval, e.g. "10 per year" or "12 in 1982". The prevalence of a condition is the proportion of a population that are cases at a point in time, e.g. "1 in 1000". [5] The incidence of disease is defined as the number of new cases of disease occurring in a population during a defined time interval. ... In epidemiology, the prevalence of a disease in a statistical population is defined as the total number of cases of the disease in the population at a given time, or the total number of cases in the population, divided by the number of individuals in the population. ...


Examples of the way information is collected to specifically measure incidence rather than prevalence include:

  • Annual and age specific incidence for first recorded diagnoses of autism (that is, when the diagnosis of autism was first recorded);
  • Annual, birth cohort specific risk of autism diagnosed[6]

New diagnostic criteria and techniques

When the rising prevalence of autism spectrum disorders sparked research in the late 1990s, medical opinion initially attributed the increase to improved diagnostic screening or changes in the definition of autism. In 1994, the fourth major revision of the Diagnostic and Statistical Manual of Mental Disorders (DSM-IV) was published[7] with updated criteria for the diagnosis of autism and autism spectrum disorders.[8] Professional medical associations, including the American Academy of Pediatrics, say that this revision was an important factor in increasing the apparent prevalence of autism and a 2005 study by Mayo Clinic researchers found increases in autism diagnoses followed the revisions in DSM criteria and changes in funding for special education programs.[9] In epidemiology, the prevalence of a disease in a statistical population is defined as the total number of cases of the disease in the population at a given time, or the total number of cases in the population, divided by the number of individuals in the population. ... Year 1994 (MCMXCIV) was a common year starting on Saturday (link will display full 1994 Gregorian calendar). ... The Diagnostic and Statistical Manual published by the American Psychiatric Association The Diagnostic and Statistical Manual of Mental Disorders (DSM) is a handbook for mental health professionals that lists different categories of mental disorder and the criteria for diagnosing them, according to the publishing organization the American Psychiatric Association. ... The American Academy of Pediatrics (AAP) is an organization of pediatricians, physicians trained to deal with the medical care of infants, children, and adolescents. ... Main campus in downtown Rochester, Minnesota. ...


An increased awareness of autistic disorders by parents and pediatricians may have also led to increased reporting of Autism due to 'case substitution', which occurs when children with other disorders are identified as autistic.[10] This misdiagnosis may occur for several reasons including an increase in government funding for care of children diagnosed as autistic, but not for children with a similar degree of disability and need . If this is occurring, it means that children who in the past would probably have been diagnosed as having a different condition, or not diagnosed at all are recorded as new cases of autistic spectrum disorder. Possible alternate diagnoses include mental retardation, learning disability and childhood schizophrenia [11]. High-functioning autistic children are sometimes misdiagnosed ADHD. [12] Children who are not primarily autistic, e.g. those with Fragile-X Syndrome (with characteristics that fit the criteria for autism) and even Down's Syndrome may have the diagnostic group with the best funding assigned.[13] Mental retardation is a term for a pattern of persistently slow learning of basic motor and language skills (milestones) during childhood, and a significantly below-normal global intellectual capacity as an adult. ... In the United States and Canada, the term learning disability (LD) is used to refer to a range of neurological conditions that affect one or more of the ways that a person takes in, stores, or uses information. ... DISCLAIMER Please remember that Wikipedia is offered for informational use only. ... Fragile X Syndrome is the most common inherited cause of mental impairment, and the most common known cause of autism. ...


Incidence in sub-groups

There have been suggestions that the incidence of autism may vary amongst particular groups defined by occupation, lifestyle or genetic isolation. Changes that made travel and communication easier, and the growth of the technological industries during the past decade, have been suggested as means for increase in the proportion of couples likely to produce an autistic child. None of these have been established.[14] [15] [16][17]


Geographical Incidence

Japan

The Yokohama study in Japan (2005) examined the incidence of autism before and after the 1993 withdrawal of MMR, reporting 48 and 86 cases per 10,000 children in two sequential years before withdrawal, doubling to 97 and 161 per 10,000 afterwards in the two years afterwards.[18][19] Year 2005 (MMV) was a common year starting on Saturday (link displays full calendar) of the Gregorian calendar. ... The MMR vaccine is a mixture of live attenuated viruses, administered via injection for immunization against measles, mumps and rubella. ...


It studied over 30,000 children (278 cases) born in one district of Yokohama.[20] For a tire company, known by Yokohama Tyre, see Yokohama Rubber Company. ...


United Kingdom

The National Autistic Society regarded the incidence and changes in incidence with time as unclear.[21] A 2001 review,[22] by the Medical Research Council, yielded an estimate of one in 166 in children under eight. The National Autistic Society (NAS) is the United Kingdoms most prominent autism-related charity. ... Year 2001 (MMI) was a common year starting on Monday (link displays the 2001 Gregorian calendar). ... Current MRC logo The Medical Research Council (MRC) is a UK organisation dedicated to promot[ing] the balanced development of medical and related biological research in the UK. // The MRC is one of seven Research Councils and is answerable to, although politically independent from, the Office of Science and Innovation...


The reported autism incidence in the UK rose starting before the first introduction of the MMR vaccine in 1989.[23] The MMR vaccine is a mixture of live attenuated viruses, administered via injection for immunization against measles, mumps and rubella. ... Year 1989 (MCMLXXXIX) was a common year starting on Sunday (link displays 1989 Gregorian calendar). ...


United States

After years of substantial annual increases, provisional data from the US Department of Education show a significant decrease in the number of new autism diagnoses recorded among children 3 to 5 years old. There were 1,451 new cases in 2001-2002; 1,981 in 2002-2003; 3,707 in 2003-2004; and 3,178 in 2004-2005, a drop of 529 new cases, or 14%.[24]

U.S. New Cases[25]
Year 2001-02 02-03 03-04 04-05
New cases 1 451 1 981 3 707 3 178

The incidence of autism increased by over 900% between 1992 and 2001, according to the United States Department of Education.[citation needed] In 1999, the autism incidence rate in the US was generally cited at 4.5 cases per 10,000 live births.[citation needed] By 2005, the US Centers for Disease Control (CDC) estimated one of every 250 babies was born with autism, or 4 cases per 1000.[citation needed] Year 1992 (MCMXCII) was a leap year starting on Wednesday (link will display full 1992 Gregorian calendar). ... Year 2001 (MMI) was a common year starting on Monday (link displays the 2001 Gregorian calendar). ... The Lyndon Baines Johnson Department of Education Building[1]) , ED headquarters in Washington, DC A construction project to repair and update the building facade at the Department of Education Headquarters building in 2002 resulted in the installation of structures at all of the entrances to protect employees and visitors from... The Centers for Disease Control and Prevention (CDC) in Atlanta is recognized as the lead United States agency for protecting the public health and safety of people by providing credible information to enhance health decisions, and promoting health through strong partnerships with state health departments and other organizations. ...


Olmsted County, Minnesota

"The incidence of research-identified autism increased in Olmsted County from 1976 to 1997, with the increase occurring among young children after the introduction of broader, more precise diagnostic criteria, increased availability of services, and increased awareness of autism." The authors ascribed this to "improved awareness, changes in diagnostic criteria, and availability of services, leading to identification of previously unrecognized young children with autism." [26]

Olmsted County: 8.2-fold increase, confined to children younger than 10 years who were born after 1987.
Period 1980-83 1995 to 1997
Age-adjusted incidence of research-identified autism 5.5 (95% confidence interval, 1.4-9.5) 44.9 (95% confidence interval, 32.9-56.9)

Denmark

In November 2002, a study reported a lower incidence of autism in Denmark than in the US and other countries. An incidence of 1 in 727 (738 out of 537,303) was reported, compared with up to 1 in 86 among primary school children in the United Kingdom and around 1 in 150 children in the USA. Danish authorities also reported a continued increase in the incidence of autism after 1992 after withdrawal of thiomersal-containing vaccines.[27] Data presented in 2003 shows a clear increase in incidence between 1990 and 1995 (before the criteria changed). Thus, the increased incidence of autism after the removal of thiomersal was not a measurement artefact,[28] nevertheless Dan Olmsted argued that this was an artefact due to a change in criteria for registration of children with autism in Denmark.[29]


Notes

  1. ^ Incidence National Autistic Society
  2. ^ Summary item in "Overlawyered archive"
  3. ^ [http://ajp.psychiatryonline.org/cgi/content/abstract/145/11/1404 DSM3 changes
  4. ^ DSM4 changes
  5. ^ British Medical Journal: Epidemiology for the Uninitiated 4th Ed: Quantifying diseases in populations BMJ
  6. ^ 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. PMID 11222420. 
  7. ^ [1]
  8. ^ [2]
  9. ^ 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". Archives of pediatrics & adolescent medicine 159 (1): 37-44. DOI:10.1001/archpedi.159.1.37. PMID 15630056. 
  10. ^ Am. Assoc. paed. Case substitution accounts for some of the increase in reported incidence
  11. ^ [3]
  12. ^ [4]
  13. ^ CNN report Dr Fred Volkmar, an autism researcher from Yale said "Autism is a kind of fashionable diagnosis".
  14. ^ Parental type
  15. ^ BBC report Simon Baron-Cohen believes that "it has become easier for systemizers to meet each other, with the advent of international conferences, greater job opportunities and more women working in these fields."
  16. ^ [5] Assortative mating has not been demonstrated in humans. The spouses of identical twins tended to find the other twin annoying rather than attractive.
  17. ^ Mearns, Int. Paed. autistic individuals have a higher proportion of engineers as close family members than the rest of the population. Speculation on job choice and phenotype.
  18. ^ Hideo Honda, Yasuo Shimizu and Michael Rutter (2005). "No effect of MMR withdrawal on the incidence of autism: a total population study". Journal of Child Psychology and Psychiatry 46 (6): 572. PMID 15877763 DOI:10.1111/j.1469-7610.2005.01425.x. 
  19. ^ Bandolier: incidence around 1993 http://www.jr2.ox.ac.uk/bandolier/booth/Vaccines/noMMR.html
  20. ^ Cited in New Scientist[6] and reviewed in Bandolier with graph of main results.
  21. ^ http://www.autism.org.uk/nas/jsp/polopoly.jsp?d=459&a=5576 Position statement, official website of National Autistic Society (UK) viewed March 2007
  22. ^ http://www.mrc.ac.uk/OurResearch/ResearchFocus/Autism/ResearchStrategy/index.htm
  23. ^ 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. PMID 11222420. 
  24. ^ [7]
  25. ^ [8]
  26. ^ http://www.ncbi.nlm.nih.gov/sites/entrez?cmd=Retrieve&db=pubmed&dopt=Abstract&list_uids=15630056
  27. ^ [9]
  28. ^ Anne-Marie Plesner, Peter H. Andersen and Preben B. Mortensen Kreesten M. Madsen, Marlene B. Lauritsen, Carsten B. Pedersen, Poul Thorsen. Thimerosal and the Occurrence of Autism: Negative Ecological Evidence From Danish Population-Based Data. Pediatrics 2003;112;604-606. PMID 12949291
  29. ^ Danish measurement artifact USA Today article by Dan Olmsted

37. Tebruegge M, Nandini V, Ritchie J. Does routine child health surveillance contribute to the early detection of children with pervasive developmental disorders? An epidemiological study in Kent, U.K. BMC Pediatr. 2004 Mar 3;4:4. The British Medical Journal (BMJ) is a medical journal published weekly in the United Kingdom by the British Medical Association (BMA)which published its first issue in 1845. ... A digital object identifier (or DOI) is a standard for persistently identifying a piece of intellectual property on a digital network and associating it with related data, the metadata, in a structured extensible way. ... Simon Baron-Cohen is a British professor of developmental psychopathology in the departments of psychiatry and experimental psychology at the University of Cambridge, a Fellow of Trinity College, Cambridge, and director of the Autism Research Centre at the University of Cambridge, in the United Kingdom. ... A digital object identifier (or DOI) is a standard for persistently identifying a piece of intellectual property on a digital network and associating it with related data, the metadata, in a structured extensible way. ... New Scientist is a weekly international science magazine covering recent developments in science and technology for a general English-speaking audience. ...


References

  • CPA-APC.org - Diagnosis and Epidemiology of Autism Spectrum Disorders Lee Tidmarsh, MD, Fred R Volkmar, MD, The Canadian Journal of Psychiatry, Vol 48 pp 517–525, 2003
  • NIH.gov - 'The changing prevalence of autism in California', L.A. Croen, J.K. Grether, J Hoogstrate, S Selvin, Journal of Autism Developmental Disorders Vol 32, No 3, pp 207-15, June, 2002
  • NIH.gov -'The epidemiology of autistic spectrum disorders: is the prevalence rising?', Lorna Wing, D. Potter, Ment Retard Dev Disabil Res Rev, Vol 8, No 3, pp 151-61, 2002
  • NIH.gov - 'The incidence of autism in Olmsted County, Minnesota, 1976-1997: results from a population-based study', W.J. Barbaresi, S.K Katusic, R.C. Colligan, A.L. Weaver, S.J. Jacobsen, Arch Pediatr Adolesc Med, Vol 159, No 1, pp 37-44, January, 2005
  • California DDS figures and reports: http://www.dds.ca.gov/FactsStats/quarterly.cfm , http://www.dds.ca.gov/autism/autism_main.cfm

External links

  • NeuroDiversity.com - Although labelled 'Prevalence of Autism' this lists references to incidence as well.
  • PediatricServices.com - 'The Autism Epidemic'
  • ScienceDaily.com - 'The Age of Autism: What epidemic?', Dan Olmsted, Science Daily (August 1, 2005)
  • ScienceDaily.com - 'The Age of Autism: The Amish anomaly', Dan Olmsted, Science Daily (April 18, 2005)
  • SFGate.com - 'State autism rate confounds experts: 273% increase in 11-year span', Katherine Seligman, San Francisco Chronicle (October 18, 2002)
  • TheAge.com.au - 'Number of disabled students soars' Chee Chee Leung The Age (April 26, 2005)
  • TMCNet.com - 'Parents say autism is an issue across the globe' (January 11, 2006)
  • Wired.com - 'The Geek Syndrome: Autism - and its milder cousin Asperger's syndrome - is surging among the children of Silicon Valley. Are math-and-tech genes to blame?' Steve Silberman Wired (December, 2001)

 
 

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