The microsegmentation of the autism spectrum: research project

6 Prevalence And Intellectual Ability: The Scottish Context

6.1 The data we have generated on prevalence and intellectual ability may be applied to the specific context of the Scottish population. On that basis it is now possible to provide accurate data for the number of individuals with ASD, together with numbers with and without intellectual disability, in every age range for the whole of Scotland and for every Council or Health Board area. It should be noted that these are the numbers on which planning should be based, that is, those who have ASD, whether diagnosed or not. At the youngest ages, it is not expected that children will yet be at the stage where diagnosis can be reliably carried out.

6.2 Table 6.1 shows these estimates in relation to the Scottish population. These population figures have been statistically adjusted to age 67 years to take account of longevity in terms of the available ASD research in this field (Shavelle & Strauss, 1998). The adjustment for longevity does not imply that individuals with autism are not to be found in older age ranges, and the data collected in the survey illustrate that point. Rather, it provides a standard method for adjusting figures to accommodate longevity statistics.

Table 6.1 Prevalence of autism in Scotland by age and intellectual disability

^a The age range for which data is reported here reflects findings from longitudinal ASD studies. For further details see para. 6.2, and for data relating to the total population see Table 6.2. ^b Total population statistics taken from ONS (2017).

6.3 Table 6.2 shows the same figures for the total adjusted population of all Scottish Council areas.

Table 6.2 Prevalence of autism by Council area and intellectual disability

^a Figures reported here are based upon the total population; for estimates reflective of longitudinal findings relating to ASD see Table 6.1, and for more information on this see para. 6.2. ^b Total population statistics taken from ONS (2017).

6.4 Table 6.3 shows the figures for the total adjusted population of each of the Health Board area in Scotland.

Table 6.3 Prevalence of autism by Health Board and intellectual disability

^a Total population statistics taken from ONS (2017)

6.5 The total relevant population figures for Council areas and Health Board areas are derived by applying the overall adjustment used for Scotland as a whole. This will show some variation across Council and Health Board areas depending on the age structure of the population in each area.

6.6 The calculations used here will provide a basis for any individual Council or Health Board to compute accurate figures for autism, both with and without intellectual disability, using any age breakdown best suited to their purposes and also adjusting figures for any given year to take account of population change. Services differ in their specific requirements. For example, the relevant age bands for education may correspond to preschool, primary, secondary and post-school populations, while Health Boards may wish to focus on age bands for child and adolescent services or other types of age-related provision. In each case the numbers may be computed by obtaining a total autism figure of 1.035% of the relevant population. From that figure, there will be a distribution of 32.7% with intellectual disability, and 67.3% without intellectual disability.