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Brief Report: Prevalence of Pervasive Developmental Disorder in Brazil: A Pilot Study

Posted Feb 23 2011 6:56pm

Real data on autism prevalence around the world is scant. Many countries do not track accurately (including the US) and few countries have reported on autism prevalence.

So, while this is only a “pilot study”, I was intrigued to read that someone was reporting on autism prevalence in Brazil:

Brief Report: Prevalence of Pervasive Developmental Disorder in Brazil: A Pilot Study .

Paula CS, Ribeiro SH, Fombonne E, Mercadante MT.

Developmental Disorder Post Graduation Program, Mackenzie Presbyterian University, Rua da Consolação, 930. Edifício 38 Secretaria de Pós-Graduação em Distúrbios do Desenvolvimento, São Paulo, SP, 01302-907, Brazil, csilvestrep09@gmail.com.
Abstract

This pilot study presents preliminary results concerning the prevalence of Pervasive Developmental Disorder (PDD) in South America. It was a three-phase study conducted in a typical town in Southeast Brazil. Case definition was based in a combination of standardized instruments and clinical evaluations by experts. The prevalence of PDD was 27.2/10,000 (95% CI: 17.6-36.8) and some hypotheses were raised to explain this low frequency. Clinical findings of PDD cases were consistent with previous data, such as, male preponderance, more children diagnosed with PDD-NOS than with autistic disorder, and half of them born from older mothers. Moreover, the study raised concerns about treatment of cases, because identification of PDD had been late and access to services has been very limited.

The prevalence is low: about 0.27% for all PDD’s. About 1/4 that of the US or the UK.

Just in this year (2011), 4 other papers have come out on autism prevalence:

Denmark and Australia : 0.685% and 0.51%, respectively.

Autism prevalence varies by race, even within a single US municipality (Atlanta) . In the San Francisco Bay area, autism prevalence is about 0.47% , and again varies with race/ethnicity. Yes, the San Francisco bay area has a prevalence about 1/2 the national average.

While more of a review, this paper discusses how autism prevalence rates vary by country

Autism prevalence estimates vary. They vary with time, they vary with place, they vary with ethnicity, they vary with socio-economic status. I don’t think it is hopeless to try to pull causation inferences from prevalence data, even administrative prevalence data like education data or the CDDS data. It is hard though. There are obviously a number of factors at play. Many social factors included. And that makes it really hard to interpret what all these data mean.

As a final aside, for those trying to work these latest data from Brazil into the “vaccine hypothesis”, the vaccine schedule for Brazil is here . They have a lot of vaccines, including the birth dose of HepB and thimerosal containing vaccines. The low prevalence in this pilot study do not support the hypothesis.

  1. Tweets that mention Autism Blog - Brief Report: Prevalence of Pervasive Developmental Disorder in Brazil: A Pilot Study « Left Brain/Right Brain -- Topsy.com:
    [...] This post was mentioned on Twitter by Brandon Blietz, Alltop Autism. Alltop Autism said: Brief Report: Prevalence of Pervasive Developmental Disorder in Brazil: A Pilot Study http://bit.ly/ewX2zD [...]

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