One of the 'hot' topics of autism research is the question of 'how many people present with an autism spectrum condition'?

I don't have the answer by the way, but there are a few recent papers which seem to be pointing at a few interesting figures. Indeed the last week or so has been an interesting time for those with an interest in the epidemiology of autism.

First there was the findings from a UK study looking at the prevalence of autism spectrum conditions in an adult population (16 years +). The paper abstract can be viewed here but the paper summary: (1) an initial autism traits screening questionnaire was completed by nearly 7,500 participants; (2) 618 participants were invited for a more detailed follow-up interview; (3) the weighted prevalence of autism spectrum disorder (ASD) in adults was estimated to be 9.8 per 1,000 (approaching 1% of the population); (4) none of those diagnosed with an ASD from the study had been previously assessed or diagnosed.

Next we have the findings from a US study of autism prevalence in Utah. The paper abstract can be viewed here. Again the summary: (1) administrative records (health and education) were analysed for children at various ages; (2) the prevalence of autism spectrum disorder (ASD) was estimated at 1 in 77 children aged 8 years old by 2008; (3) Utah data has been previously the subject of autism prevalence tracking with the 2008 estimates showing a 100% increase in prevalence compared with 2002 records (1 in 133) and greater still compared with late 1980s records (1 in 2,500).

Finally we have the findings from a study based on a South Korean cohort. The paper abstract can be viewed here.  The summary: (1) potential autism cases were screened from a population of 55,000 children aged 7-12 years old; (2) positive screen cases were followed-up with a more extenstive diagnostic assessment; (3) the prevalence of ASD was estimated to be 2.64% (calculated as 1 in 38 children); (4) depending on whether a general population or at-risk group were screened, there were differences in the prevalence rate suggesting that approximately two-thirds of cases were in mainstream school "undiagnosed and untreated".

There is a lot of discussion about these studies individually at the moment. It would be easy to draw quick conclusions from the various data but, as always, caution is required in making any firm statements not least because each follows a different geographic group and various methods were used to ascertain cases.

Again, watch this space.