Reviewing the Autism Prevalence (The Epidemiology: Part 1)
The (1) in 166 children, which converts to (60) in 10,000, was a rough estimate given by the Center for Disease Control based on several epidemiological studies they helped conduct (Center for Disease Control, 2005). The Metropolitan Atlanta Developmental Disabilities Surveillance Program (MADDSP) found (20-30) per 10,000 children had an Autism Spectrum Disorder (Boyle, Yeargin-Allsop, Doernberg, Holmgreen, Murphy, & Schendel, 1996). The CDC website also discusses (Bertrand et al., 2001) which found a prevalence of (67) per 10,000 for the autism spectrum and (40) per 10,000 for Autistic Disorder. Only (Bertrand, Mars, Boyle, Bove, Yeargin-Allsop, & Decoufle, 2001) found near (60) per 10,000. The other studies the CDC helped conduct were lower.
Bertrand et al., (2001), like the 3 other studies that produced high prevalence rates (Kadesjo et al., 1999; Baird et al., 2000; Chakrabarti, & Fombonne, 2001) were noted to have small sampling populations (Fombonne, 2003).
I have concerns about the prevalence given by Bertrand et al., (2001). The CDC was aware of a potentially higher incidence in this township as they were going into this city (CDC, 2005; Fombonne, 2003). Originally I had felt that while the data taken from this township might be appropriate for setting the upper limit of autism spectrum prevalence, it might be harmful if applied universally.
Yeargin-Allsopp, Rice, Karapurka, Doernberg, Boyle, Murphy (2003) provides another recent US study to compare to for Autistic Disorder. They found a prevalence of (34) per 10,000. This is lower than the results found by (Bertrand et al., 2001).
However, a recent developments alleviates my concerns and seem to indicate that the (60) per 10,000 is an appropriate prevalence rate. Chakrabarti & Fombonne, (2005) compare a recent cohort to a previous study (measured from 1992-1995) which they conducted in the identical geographical area in the United Kingdom. They conclude that the prevalence rate is high, but stable at (62) per 10,000. And the new study with a sampling population of (10,903) is notably high and resolves my concern about other studies small sampling populations.
The difference between the prevalence rates calculated in the United Kingdom based Chakrabarti & Fombonne, (2005) and United States Bertrand et al., (2001) are insignificant. Dr.s Chakrabarti and Fombonne have convincingly shown that the autism spectrum prevalence rate is high, stable across time, and international. This seriously calls into question the validity of the concept of an epidemic of autism.
Baird, G., Charman, T., Baron-Cohen, S., et al. (2000). A screening instrument for autism at 18 months of age: a 6 year follow-up study. Journal of American Academy of Child and Adolescent Psychiatry 39, 694-702.
Bertrand, J., Mars, A., Boyle, C., Bove, F., Yeargin-Allsop, M., & Decoufle, P. (2001). Pediatrics, 108, 1155-161.
Boyle CA, Yeargin-Allsop M, Doernberg NS, Holmgreen P. Murphy, CC & Schendel, DE. (1996) Prevalence of selected developmental disabilities in children 3-10 year of age: The Metropolitan Atlanta Developmental Disabilities Surveillance Program. MMWR Morbidity and Mortality Weekly Reports. 45 (SS-2):1-14.
Chakrabarti, S., & Fombonne, E. (2001). Pervasive developmental disorders in preschool children. Journal of the American Medical Association, 285, 3093-3099.
Chakrabarti, S., Fombonne, E., (2005). Pervasive developmental disorders in preschool children: confirmation of high prevalence. American Journal of Psychiatry, 162(6), 1133-41
Kadesjö, B., Gillberg, C., & Hagberg, B. (1999). Autism and Asperger syndrome in
seven-year old children. A total population study. Journal of Autism & Developmental Disorders, Vol 29(4), 327-331
Yeargin-Allsopp, M., Rice, C., Karapurka, T., Doernberg, N., Boyle, C., Murphy, C. (2003). Prevalence of autism in a US metropolitan area. Journal of the American Medical Association, 289, 49-89.