Tuesday 5 April 2011

Prevalence and incidence of autism in Taiwan

Only a quick post this one on what is a gorgeous sunny day outside.
An early first article has appeared on-line at the Journal of Child Neurology titled: Prevalence and incidence of autism spectrum disorders among National Health Insurance enrollees in Taiwan from 1996 to 2005.
It is another look at the numbers of autism spectrum conditions but this time from a country outside of the "Western, industrialised" team. The main findings are that prevalence of autism, as measured by health service use, increased between 1996 and 2005 from 1.79 per 10,000 to 28.72 per 10,000 in Taiwan. More importantly, incidence (often a point of contention in autism) increased from 0.91 to 4.41 per 10,000 per year from 1997 to 2005. The greatest increase in incidence was in the 0-5 year age group (males).
What does it all mean?
Well, first of all it suggests that the numbers of cases of diagnosed autism were rising, and seemingly rising pretty fast in Taiwan over quite a short period of time (less than 10 years). It also suggests that the risk of being diagnosed with an autism spectrum condition was also increasing; again over a comparatively short period of time.
The fact that increasing incidence was noted for the younger age group (0-5 years) is important because it means that risk of autism diagnosis was greatest for this younger age group. This might have some implication for suggestions about increasing numbers being partially due to diagnosis in later childhood or adulthood (I stress 'might').
The authors of the Taiwan study also mention higher incidence in urban areas which could also be of some interest (whether due to geographic service provision or a role for some environmental factors).
The down-side to the data: well it was based on a database of service use, which might suggest that it misses cases where such services are not used (or not reported to be used); hence representing an under-estimation of cases (I don't know enough about the Taiwanese healthcare system to comment further).
It also looks like they did not go out and confirm the accuracy of the diagnosis, rather reliant on assessments for autism being accurately completed (although other papers from Taiwan suggest diagnostic provisions should not be under-estimated). I talked about diagnosis and diagnostic stability previously.
As the years push on and we spend longer with our current ICD and DSM diagnostic manual versions - nearly 20 years with each manual, it should mean that we start to get a clearer picture on prevalence and incidence worldwide without interference from things like changing diagnostic criteria.
If, as appears to be the trend, prevalence and incidence of autism is increasing worldwide, serious questions need to be asked about the possible factors governing such a change in numbers and perhaps more importantly, the provisions in place / to be put in place to ensure adequate services for all those diagnosed, particularly in these times of austerity.

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