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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. 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. 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: Incidence National Autistic Society
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". British Medical Journal : Epidemiology for the Uninitiated 4th Ed: Quantifying diseases in populations BMJ Examples of the way information is collected to specifically measure incidence rather than prevalence include:
NEW DIAGNOSTIC CRITERIA AND TECHNIQUES When the rising , 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.2 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. Am. Assoc. paed. Case substitution accounts for some of the increase in reported incidence 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 . 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.[http://edition.cnn.com/2003/HEALTH/conditions/03/02/autism.ap/ CNN report Dr Fred Volkmar, an autism researcher from Yale said "Autism is a kind of fashionable diagnosis". 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. Parental type 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." Assortative mating has not been demonstrated in humans. The spouses of identical twins tended to find the other twin annoying rather than attractive.[http://www.int-pediatrics.org/PDF/Volume%2017/17-1/pd%2060-61%20mearns.pdf 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. GEOGRAPHICAL INCIDENCE Japan | ||
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