Autism prevalence

Newschaffer CJ, Falb MD, Gurney JG (2005) National autism prevalence trends from United States special education. Pediatrics, 115(3) e277-282. 

Autism prevalence data from around the world and, indeed, even within individual countries and states, are sporadic, but they indicate rising rates almost everywhere. For example, autism rates in Iceland increased from 3.8 per 10,000 in the period of 1973-83 to 8.6 per 10,000 in the period of 1984-93.111 Thirty-one cases of autism per 10,000 births were reported in Sweden in the 1990s I12l an autism rate of 11.3 per 10,000 births was reported for people native to southern Japan 13 and rates of 30 per 10,000 in U.S. metropolitan areas was reported in 2003J14 ... 

The available data, however, points in the direction that autism prevalence is lower in rural than in urban areas within the same locale. Autism is prevalent at the rate of 3.06 per 10,000 in the urban areas of Kukishama-Ken... 

Table 20.1 Autism Prevalence Rates for California, 2003-4, Population Data, and Autism Cases per 1,000,000 Population in 2004... 

It is suggested here that the dramatic increase in autism in California is due to environmental factors. The highly populated areas of California have poor air and water quality, contain numerous neurotoxic chemicals, 60 641 and are in close proximity to numerous Superfund sitesJ751 This is particularly the case in the Los Angeles area. The recent study connecting increased autism prevalence to maternal organochlorine pesticide exposure in rural California areas 59 supports the relationship between exposures to environmental pollutants and autism. Residents of urban areas are... 

Richdale, AL (1999) Sleep problems in autism prevalence, cause and intervention. Dev Med Child Neurol 41 60-66. 

The available data, however, point in the direction that autism prevalence is lower in rural than in urban areas within the same locale. Autism is prevalent at the rate of 3.06 per 10,000 in the urban areas of Kukishama-Ken in northern Japan and at a rate of 1.18 per 10,000 in rural areas of this region [17]. In this study, it was noted that autism rates were lower when parents worked in agriculture, forestry, fishing, or mining, aU presumably rural areas. Among the indigenous peoples of Africa, autism rates are lower than in other parts of the world [8]. 

The developmental neurotoxicity guideline, accepted by OECD in 2007, has added the important aspect of behavioral effects of pre- and postnatal exposure to chemicals. This development arose from the notion that behavioral disorders in man such as anxiety, depression, phobias, autism, and attention deficit hyperactivity disorder, which appear to show increasing prevalences in western societies, may have a perinatal origin (4, 5). In the absence of causal inferences with respect to chemicals it seems nevertheless prudent to assess in a risk assessment whether such causal relations may exist. 

Children with pervasive developmental disorders are also at higher risk for developing TS. In a recent survey of 447 pupils from nine schools for children and adolescents with autism, 19 children were found to have definite TS, yielding a prevalence rate of 4.3% (Baron-Cohen et ah, 1999). However, caution is warranted, as complex motor tics can be difficult to distinguish from motor stereotypies, and differentiation among these behaviors may be especially problematic among retarded individuals with limited verbal skills. 

Baron-Cohen, S., Scahill, V.L., Izaguirre, J., Hornsey, H., and Robertson, M.M. (1999) The prevalence of Gilles de la Tourette syndrome in children and adolescents with autism a large scale study. Psychol Med 29 1151-1159. 

Sugiyama, T, and Abe, T. (1989) The prevalence of autism in Nagoya, Japan a total population study. / Autism Dev Disord 19, 87-96. 

Bednar I, Paterson D, Marutle A, Pham TM, Svedberg M, HeUstrom-Lindahl E, Mousavi M, Court J, Morris C, Perry E, Mohammed A, Zhang X, Nordberg A (2002) Selective nicotinic receptor consequences in APP(SWE) transgenic mice. Mol Cell Neurosci 20 354-365 Bejerot S, Nylander L (2003) Low prevalence of smoking in patients with autism spectrum disorders. Psychiatry Res 119 177-182... 

It should be noted that these prevalence rates may be underestimates of mental illness in the United States. First, the sample drawn was household listings and thus did not include individuals who were homeless or institutionalized (such as in nursing homes or psychiatric hospitals). Second, the study did not assess some less common psychiatric disorders, such as schizophrenia and autism. 

Our inability to defend ourselves against new chemicals and mixtures often results in epidemics of disease. For example, asthma, autism, infertility, and many cancers affect different parts of the body and seemingly have different etiologies. All, however, can be related to a combination of genetic predisposition and environmental exposure to chemicals. All are less prevalent where chemical exposures are lower, for example, in rural areas. All have known single chemical exposure causes and they can all be related to low level exposure to chemical mixtures. The toxic effects of chemical mixtures are explored in the chapters that follow. 

It is often difficult to ascribe neurodevelopmental deficits to chemical exposure only. Genetic makeup predisposes some individuals to chemical insult effects. Autism and ADHD are two prominent examples of developmental conditions that fit such a hypothesis. Both affect large numbers of children and their prevalences can be linked to environmental chemical exposures. These are discussed in the following chapters. 

It is generally agreed that autism has been increasing worldwide at least since 1979 at a rate of 3.8% per yearJ15,16 As of 2002, the conservative estimate of worldwide prevalence was 10/10,000 birthsJ17 ... 

In a study in Southern Japan, the prevalence rate for natives to the area was 11.3 per 10,000 births. The rate for migrants to the same area was 17.6 per 10,000 births. The native rates fluctuated from year to year in a 4-year cycle, whereas the migrant rates did not. In this study, children born in the second quarter of the year had a higher rate of autism than those born in other times of the year. It was also found that the prevalence of autism was closely related to the number of hospital admissions for pneumonia and bronchitis... 

Lotter reported that though autism is found in the indigenous people of Africa, the prevalence seems to be less than in more developed parts of the world. He also reported that the prevalence of autism in Africa was less in the rural areas than in the urban areas of the continent Here again, the greater preponderance of autism in urban than in rural areas cannot be attributed to genetics. 

Autism certainly has a genetic factor associated with it. Studies, however, showing seasonal and annual variations in its prevalence, increased prevalence in urban versus rural areas, increased prevalence in areas with increased environmental pollution, and increased prevalence in offspring of mothers who have taken certain drugs, leads to the conclusion that there is a connection between maternal environmental exposure to neurotoxic chemicals and the prevalence of autism. 

Tanoue Y, Oda S, Asano F, Kawashima K. Epidemiology of infantile autism in southern Ibaraki, Japan Differences in prevalence in birth cohorts. J Autism Dev Disord 1988 18(2)455-66. 

Centers for Disease Control and Prevention. Prevalence of autism in Brick Township, New Jersey, 1988 Community report, Atlanta, GA, April 2000. 

Concerns have also been raised about the possible relationship between Hg exposure from vaccines and autistic disorders. In the United States, the prevalence of autism has risen from 1 in approximately 2500 in the mid 1980s to 1 in approximately 300 children in the midl990s. Several investigators believe that this rise is because of the Hg that is... 

Autism is now considered one of the most common disorders of development worldwide. Studies performed by the United States Centers for Disease Control (CDC) in selected communities in 2002 suggest that the current prevalence rates for ASD are approximately 1 in 150 children (Kuehn, 2007). The increase in the reported prevalence of ASD has been attributed by some to improved ascertainment, a broadening of the diagnostic definition, and improved public and professional... 

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