Posted on August 19, 2011 by childhealthsafety
People who use the argument that there is no real increase in autism start out usually by using incorrect terminology. They speak of “higher functioning autism” like Asperger syndrome. It is a common mistake [or done deliberately].
“Autism” refers to what is known variously as “typical”, “Kanner”, “childhood” “classic” or “infantile” autism and that is the benchmark. Not the “higher functioning” kind others try to lump in with it like Asperger’s Syndrome. Autism makes up around 30% of UK autistic spectrum cases and Aspergers around 70%.
So if you stick to autism the paper Reichenberg et al “Advancing Paternal Age and Autism” Arch Gen Psychiatry. 2006;63:1026-1032 helpfully demonstrates this. It shows real increases in autism by establishing a benchmark for comparing mid 1980’s autism prevalence with mid 1990’s. This was done using contemporary diagnostic criteria under DSM IV. So that helpfully eliminates the argument that modern criteria are wider and so the increase is not simply a matter of definition but real.
The Paternal Age study’s PDD prevalence is 8.4:10,000 in 132,000 Israeli citizens born during six years ending no later than 1988. The authors say most of the diagnoses are autism. “PDD”or “Pervasive Developmental Disorder” under DSM IV is another term for Autistic Spectrum Disorder under the International Classification of Disease [ICD].
And we can compare that prevalence to papers like Baird 2006 [Baird G, Simonoff E, Pickles A, Chandler S, Loucas T, Meldrum D, Charman T. Prevalence of disorders of the autism spectrum in a population cohort of children in South Thames: the Special Needs and Autism Project (SNAP). Lancet. 2006:15;368:210-215.]
Baird 2006’s range of figures concern 56,946 UK children aged 9-10 years born in a two year period ending no later than 1996 and for autism provides two estimates:-
- - 24.8:10,000 (17.6-32.0) for narrow definition autism
- - 38.9:10,000 (95% CI 29.9-47.8) for autism
Baird 2006 provides estimates of a 116.1:10,000 (90.4-141.8) for the total PDD figure [autism, Aspergers etc] and 77.2:10,000 (52.1-102.3) excluding autism.
Baird 2006’s narrow definition figure is the most conservative. It meets autism criteria under DSM IV/ICD10, but also on both ADI and ADOS plus clinical judgement.
These two papers in combination assist to establish a conservative minimum 300% increase in 8 years 1988 to 1996 on Baird 2006’s narrow definition and 450% for autism. For all PDDs, these papers suggest a 1200% increase. Baird 2006 provides estimates of a 116.1:10,000 (90.4-141.8) total PDD figure and 77.2:10,000 (52.1-102.3) excluding autism against the Paternal Age paper’s figures.
Also the Reichenberg paper demonstrates how modern medical professionals go to peripheral issues thereby burying the bigger issue. The authors focussed on just 3% of fathers in their study [diverting from the more interesting finding noted above] to claim on somewhat shaky data that fathers over 40 are more likely to father an autisitic child. The confidence interval was wide [95% confidence interval, 2.65-12.46]
The problem for them is that these numbers cannot account for the scale of the increase in children born after 1988 which is what papers like Baird 2006 deal with. And it also cannot account for the Cambridge University study that found a rate of 1:64 for all autistic spectrum cases [157 per 10 000] when yet to be undiagnosed cases were included. This means 1 in 40 boys as 4 in 5 ASC cases are boys. Baron-Cohen S et al Prevalence of autism-spectrum conditions: UK school-based population study. Br J Psychiatry. 2009 Jun;194(6):500-9.