Facts and figures
Page Last updated 09-04-2009
Overall prevalence of ASD
It is currently extremely difficult to determine the number of adults living in Newcastle with ASD. At all levels, statistics about the prevalence of ASD are limited and this is particularly the case for adults with ASD. Loynes (2001) noted that there are no accurate national figures about the prevalence of ASD in general. Despite some progress in relation to the population of children, there has been no robust study of the number of adults with ASD (Parliamentary Office of Science & Technology, 2008) . However, a government funded study to calculate the number of adults with ASD in England is currently being undertaken . As a result, it is extremely difficult to precisely quantify the total number of people with ASD in Britain. In this context, the calculations regarding prevalence detailed below should be treated with a degree of caution.
At present, the best estimates of the prevalence of ASD are based on studies that focus on the ASD population as a whole, although there is still a degree of variation in the prevalence rates quoted. For example:
- In 2001, analysis of several key research studies had led to an assumption that approximately 1 in 110 people have some form of ASD .
- However, a more recent Office of National Statistics survey (2005) indicated that 0.9% of the school age population have ASD.
- A further 2006 study conducted in the South Thames region showed a prevalence rate of 116 per 10,000 for all ASDs .
These studies indicate how difficult it is to accurately estimate the prevalence rate of ASD. This is of course linked to fact that the different methodologies and approaches employed in these studies may produce different prevalence rates. However, based on analysis of available data, the National Autistic Society estimates that that the ASD prevalence rate for children is 1 in 100. Estimates suggest that there could be between 500,000 and 600,000 people with Autism in the UK and these figures are used for the purposes of this report.
Prevalence in relation to the ASD scale
As the National Autistic Society makes clear differences in definitions, difficulties defining particular sub-groups within the autism scale and the lack of clear boundaries separating ‘typical’ autism from other autism spectrum disorders make it difficult to develop an accurate calculation of the number of people with ASD . This also makes it difficult to calculate the number and proportion of those on the ASD scale with a particular type of autistic disorder.
The 1997 National Autistic Society report ‘How many people have autistic spectrum disorders?’ breaks down the prevalence rate of 91 per 10,000 into those with and without learning disabilities (see below):
Table 1: Learning Disability (IQ below 70 Approx. rate per 10,000)
Table 2: Learning Disability (IQ 70 or above Approx. rate per 10,000
It is therefore not possible to accurately calculate the national or local level population with specific types of ASD and link this to service provision and commissioning decisions.
Demographic trends
In terms of other identified demographic variations, there is relatively limited reliable evidence.
Ethnic minorities
At present, information on the prevalence of autism spectrum disorders (ASDs) among the black and minority ethnic population is not centrally collected. The Medical Research Council's (MRC) "Review of Autism Research" (2001), states that it is unclear whether people of particular racial origins are more at risk of ASDs. However, interestingly, some ethnic differences in prevalence of autism have been identified in population studies both in the UK and other countries. In Sweden, autism among the immigrant populations was found to be higher than the host population and here in the UK, there also appears to be evidence that autism in higher numbers is found in Afro-Caribbean groups , although the reason for these findings is unclear.
There are various theories as to why this gender gap occurs. For example, it is thought that in general, boys tend to have a greater expression of social deficits, whereas girls tend to be relatively more able in social play and have a more even profile of social skills. Girls seem to be more able to follow social actions by delayed imitation which perhaps disguise the symptoms of Asperger's Syndrome. In relation to gender, it is known that ASDs are more common in males than females. Various rates are quoted in the research but in general, ASD appears to occur at a rate of four males for every female (National Autistic Society). In relation to Asperger’s Syndrome, it had been thought until recently, that this ratio was far higher. Certainly, in the context of referrals, the male to female ratio for a diagnostic assessment for this condition is approximately 10:1. However, the evidence indicates that the actual ratio of diagnosed children is 4:1 (male: female) which is the same ratio as occurs with ‘classic’ autism.
Gender
In relation to gender, it is known that ASDs are more common in males than females. Various rates are quoted in the research but in general, ASD appears to occur at a rate of four males for every female (National Autistic Society). In relation to Asperger’s Syndrome, it had been thought until recently, that this ratio was far higher. Certainly, in the context of referrals, the male to female ratio for a diagnostic assessment for this condition is approximately 10:1. However, the evidence indicates that the actual ratio of diagnosed children is 4:1 (male: female) which is the same ratio as occurs with ‘classic’ autism.
There are various theories as to why this gender gap occurs. For example, it is thought that in general, boys tend to have a greater expression of social deficits, whereas girls tend to be relatively more able in social play and have a more even profile of social skills. Girls seem to be more able to follow social actions by delayed imitation which perhaps disguise the symptoms of Asperger's Syndrome.
Genetic links
The genetic basis for autism appears to be well recognised through family and twin studies. Results of twin studies imply that, when taken together with the population base rate for autism, the heritability or the underlying genetic liability is about 90% . This is the highest figure known among all multi-factorial child psychiatric disorders. An infant with an older sibling with autism has a 1 in 20 chance of developing the disorder. The inference from twin and family studies is that there are 3 to 12 susceptibility genes for autism acting synergistically . However, the genetic basis does not account for the higher prevalence of ASD in males.
Ethnic minorities
At present, information on the prevalence of autism spectrum disorders (ASDs) among the black and minority ethnic population is not centrally collected. The Medical Research Council's (MRC) "Review of Autism Research" (2001), states that it is unclear whether people of particular racial origins are more at risk of ASDs. However, interestingly, some ethnic differences in prevalence of autism have been identified in population studies both in the UK and other countries. In Sweden, autism among the immigrant populations was found to be higher than the host population and here in the UK, there also appears to be evidence that autism in higher numbers is found in Afro-Caribbean groups , although the reason for these findings is unclear.
Current ASD population in Newcastle
Based on the population data for Newcastle upon Tyne and the above prevalence figures quoted in previous research, it is possible to estimate what the expected ASD population in Newcastle could be.
- Nationally, it has been estimated that approximately 500,000 to 600,000 people have ASDs in the UK from a total population of 60,975,000 (ONS, 2007) which equates to a prevalence rate of from 0.82% to 0.98% of the population respectively .
- The population of Newcastle is approximately 271, 600 . Using a prevalence rate of 0.82%, it can be roughly estimated that approximately 2,227 people living in Newcastle have ASDs.
- Using the 0.82% prevalence rate and subtracting non-adults (in this instance 42,500 people aged below the age of 15 due to the age categories used by the data source), it can be estimated that there are approximately 1,879 adults living in Newcastle with ASDs.
- Using a prevalence rate of 0.98% and using the same data and calculations, would result in approximately 2,245 adults living Newcastle with ASDs.
However, as these prevalence figures are lower than that estimated by some other research, it is appropriate for any commissioning strategy and commissioners to regard this as a minimum figure for the prevalence of ASD in Newcastle.