Autism (incidence)

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See autism for everything, except the incidence and change in incidence, of autism.

The reported incidence of autism increased from the mid-1990s.

Uncertainty persists on the extent to which changes in the reported incidence of autism noted in the mid 1990s are accounted for by a change in the number of cases rather than changed definitions, screening, improved recording and more frequent diagnoses including artifacts due to service provision.

[9] [10]

For causes of autism see autism

The diagnostic categories in the Diagnostic and Statistical Manual of Mental Disorders have not been constant, particualrly changes in DSM-III-R[1] and DSM-IV [2]

Bayesian and Political rejection of a term

Most mainstream scientists regard the concept of an "autism epidemic" skeptically, and are joined in distaste for the term by the autism rights movement who reject any laebl implying that autism is a disability or disease.


Background

No diagnoses of autism were made before the 1940s - when it was first described as a distinct condition - with the possibility of diagnosis and the population of clinicians attracting patients with it increased steadily thereafter. In the developed world medical and population data recording became significantly more organised in the 1990s with clinical coding becoming more widespread and comprehensive as a result of technical enabling changes and and organisational pressures. The organisation of information in general, and of interest and action groups became significantly easier and individual paticipation more common in the latter half of the decade, following the introduction of the Web by Tim Berners Lee in 1993.

The number of diagnoses related to autism has increased in recent decades but public health organizations and researchers have not yet determined the relative extents to which:

  • More complete pickup of autism, as a result of increased awareness of the disorder
  • The diagnosis is being applied more broadly than before, as a result of the changing definition of the disorder
  • The underlying condition has a changing incidence with time, or prevalence in successive cohorts.
  • Successively earlier diagnosis in each succeeding cohort of children including recognition in nursery (preschool)

contribute to or confound the statistics.

Whether the true incidence of autism had been increasing was unclear as recently as 1999[3].

An increase in the recorded prevalence of autism has lead to the initiation of a number of new treatment programs, advocacy groups and support programs. In the US and UK attempts to sue vaccine companies may also increase case-reporting.[4]


Incidence in sub-groups

Various suggestions that the incidence among particular groups by occupation have been made. The change in ease of travel and communication and growth of the high-tech industries has been suggested as a means for the proportion of couples likely to produce an autistic child to increase in the time period of interest[5].


Countries with the general pattern

Australia where a ten-fold rise in diagnoses have been made in the past decade.[6] The Australian Education Department reported a 276 percent rise in students with autism spectrum disorder between 2000 and 2005. As of 2005, a total of 23,083 Victorian students were placed in school disability and language disorder programs, rising 74 per cent from 13,257 students in 2000. The figures were repportedly "a significant underestimate."[7]

Japan The Yokohama study (2005) examined autism trends before and after the 1993 withdrawal of MMR reporting 48 and 86 cases per 10,000 children in two sequential years prior to withdrawal, doubling to 97 and 161 per 10,000 afterwards in two seqeuential years afterwards.[8]

According to Vaccination News, one in eighty-six primary school children in the United Kingdom has autism, compared with one in 2,200 in 1988.[11] Another estimate of the UK incidence rate came from the National Autistic Society, which estimated autism spectrum disorders in the total population to be one in 110. A 2001 review, by the Medical Research Council, yielded an estimate of one in 166 in children under eight.

According to statistics cited by Bernard Rimland, the autism rate in the UK suddenly spiked after the first introduction of the MMR vaccine in 1989, just as it had after the MMR's introduction in the US in the late 1970s.[12]. This is not consistent with evidence published in the British Medical Journal.[13]

Substantial funds (over £3 million) were spent in the UK on a pro-MMR campaign.[14] Concerted efforts have been made by the British government and pharmaceutical industry interests to negate the widely criticized 1998 study, led by Dr. Wakefield, that showed a consistent set of bowel disorders among a dozen autistic children.[15] The study authors also suggested the need for further studies into the apparent link between MMR and autism, although 10 of Wakefield's co-authors retracted the recomendation six years later.

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%.[16]

USA Prevalence

A recent estimate by the National Autism Association is of approximately 500,000 autistic spectrum cases in the United States, including perhaps as many as 1 in 150 children. Anne McElroy Dachel of the NAA noted 80% of autistic Americans are under the age of 18.

Autism grew by over 900% between 1992 and 2001, according to data from the United States Department of Education. In 1999, the autism incidence rate in the US was generally cited at 4.5 cases per 10,000 live births. By 2005, the US Centers for Disease Control (CDC) estimates one of every 250 babies is born with autism, or 40 cases per 10,000.

The rising enrollments in special education classes in the nation's public school system provide another estimate of prevalence, subject to confounding factors. In Ohio in 1992-93, there were only 22 reported cases of autism, but by 2003-04 there were 5,146; in Illinois, there were five cases in 1992-93, and 6,005 in 2003-04; in Wisconsin, 18 cases of autism in 1992-93 and 3,259 in 2003-04.[9]

As many as 1.5 million Americans may have some form of autism, including milder variants, and the number is rising. Epidemiologists estimate the number of autistic children in the US could reach 4 million in the next decade.[10]

Connecticut

The number of autistic children educated at public expense in Connecticut has increased 325 percent since 1996, according to the State Department of Education. Governor M. Jodi Rell included a 38 percent increase, to $25.5 million, in the State's budget, for reimbursement to local schools for special education costs.

New Jersey

New Jersey has a high number of autistic children. A significant portion of the autistic children in New Jersey, were either born in other States or have parents from another State; many more autistic children may have moved to New Jersey from other states specifically because of its well known special education system.

Pennsylvania

74,000 Pennsylvanians diagnosed with autism spectrum disorders.[11]

Amish anomaly

An apparent anomaly among Amish populations was reported in 2005. Although a formal study has not yet been conducted, efforts to assess the prevalence of autism in the Amish community turned up only a very few cases. About 22,000 Amish live in Lancaster County, yet only three or four Amish with autism have turned up thus far in an informal survey of Lancaster County, whereas dozens would be expected at the 1-in-166 prevalence in society at large. "You'll find all the other stuff, but we don't find the autism," according to Dr. Frank Noonan, a Lancaster County family doctor, adding "We're right in the heart of Amish country and seeing none."

In June, 2005, William F. Raub, of the Department of Health and Human Services, suggested the possibility of launching studies of the Amish in response reports of a low prevalence of autism in that community.[17]

Since vaccinations are virtually unheard of in the Amish, these preliminary findings have sparked further speculation about the vaccine-autism link. However, note is made of potential for substantial confounding with other aspects of Amish lifestyle and genetic homogeneity.


Countries where the general pattern is not clearly apparent

China In a July, 2005, interview Robert F. Kennedy, Jr. stated that, "six years ago, autism was unknown in China. We started giving them our vaccines in 1999. Today there's 1.8 million cases of autism in China."[18] Shanghai alone has over 10,000 known autistic children.[19] However, this seems to conflict with a 1997 study, in China, about teaching Chinese to autistic children, [20] as well as a 1991 study of a Chinese "calendar savant". [21]

Denmark The incidence of autism reported in the study published in November 2002 was lower than the US and other countries. Incidence rate of 1 out of 727 (or 738 out of 537,303) was reported, far less than estimates of up to 1 in 86 among primary school children in the United Kingdom and around 1 out of 150 children in the US. Danish authorities report a continued increase in the incidence of autism after 1992 [12] (when they eliminated Thimerosal. However around that time Danish criteria for registration of children with Autism changed, increasing the proportion (by a factor of 5 according to one source)[13]

Russia The Russian autism rate did not change for at least a decade after 1985 (when Thimerosal was abandoned.[14]

California

California is considered[citation needed] to have the best reporting system for autism in the US. According to data released in late 2005 by the California Department of Developmental Services (DDS), new cases — of professionally diagnosed full syndrome DSM IV autism — entering the DDS system indicated a decline, from 734 new cases during the second quarter of 2005 to 678 new cases during the third quarter of 2005, a 7.5% decline in one quarter.

As of August 1993, a total of only 4,911 cases of autism had been logged in DDS's client-management system, a number excluding milder autism spectrum disorders, such as Asperger's syndrome. By April 29, 1999, the DDS reported a State-wide incidence rate of about 15 to 20 per 10,000, triggering alarms about the staggering increase.

As of 2005, the DDS reported a total of 28,046 cases, but that the rate of increase peaked in 2002 and has dropped slightly since then. According to data released by DDS in January, 2006, the number of new cases of professionally diagnosed full syndrome autism entering California's developmental services system in 2005 was the smallest since 2001. The DDS year end report documents that, during 2005, California added 2,848 new cases of autism to its system. Not since 2001, when 2,725 new cases were added, has California added fewer new cases of full syndrome autism to its system. Ever since the record year of 2002, there has been a slow, steady decline in the number of new autism cases entering the 37-year old DDS system, even though levels have still not yet reached the 1 in 166 reported by population-based studies.

The use of the term "New Cases" has come into question and DDS itself has documented that "New Cases" should not be calculated as the difference in the numbers between quarters [22]. The total caseload handled by the state continues to increase at a pace much higher than population growth, but the recent trend points to a decrease in the caseload increase per quarter. The decline has been speculated to coincide with vaccines containing thimerosal being phased out in recent years. It could also indicate that the awareness curve is starting to level off. It has also been pointed out that the caseload does not yet meet the levels found in population studies.

According to a report by the DDS [15] the rate of children diagnosed with full-syndrome autism in California nearly doubled between 1999 and 2002, from 10,360 to 20,377. The report stated, "(B)etween Dec. 31, 1987, and Dec. 31, 2002, the population of persons with full-syndrome autism has increased by 634 percent."

California's increase in childhood autism was not due to flawed diagnoses, according to a 2002 study led by University of California, Davis pediatric epidemiologist Robert Byrd. 1,685 newly diagnosed autistic children had entered the state's regional center system the previous year, marking a 273 percent increase over an 11-year period from 1988 to 1999. The data again included only children with classic autism, discounting those with PDD-NOS, Asperger's, etc. "The sheer complexity of this phenomenon prevents any clear conclusions," the report stated. "What we do know is that the number of young children coming into the system each year is significantly greater than in the past."

Granite Bay cluster

In 1999, in Granite Bay, California, 22 of the 2,930 children enrolled in grades K-6 were autistic.

Silicon Valley cluster

A 2002 BBC article indicated that one in 150 children in the region had an autistic spectrum disorder. A 2001 article in Wired suggested that the cluster is a result of a link between autistic disorders and computer skills.



References

  1. ^ [http://ajp.psychiatryonline.org/cgi/content/abstract/145/11/1404 DSM3 changes
  2. ^ DSM4 changes
  3. ^ Incidence
  4. ^ [1]
  5. ^ Parental type
  6. ^ [2]
  7. ^ Sydney Children's Hospital
  8. ^ [3]
  9. ^ [4]
  10. ^ [5]
  11. ^ [6]
  12. ^ [7]
  13. ^ Danish measurment artifact
  14. ^ [8]
  15. ^ Autistic Spectrum Disorders, Changes in the California Caseload: 1999-2002
  • 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 - 'Prevalence of autistic spectrum disorders in Lothian, Scotland: An estimate using the 'capture-recapture' technique', M.J. Harrison, A O'Hare, H. Campbell, A. Adamson, J McNeillage, Arch Dis Child. May 10, 2005
  • 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

External links


  • 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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