Autism’s Increased Incidence Research

Explore recent research addressing the increasing incidence of autism.

Investigation of shifts in autism reporting in the California Department of Developmental Services.
Grether JK, Rosen NJ, Smith KS, Croen LA.
J Autism Dev Disord. 2009 Oct;39(10):1412-9. [Epub 2009 May 29.]

The authors investigate if the shifts in the coding of qualifying conditions in the California Department of Developmental Services (DDS) have contributed to the increase in California children with autism observed in recent years. They did not find evidence of a coding shift or an increase in the proportion of children with coded autism who lacked supportive diagnostic documentation in records (possible "misclassifications"). These results indicate that changes in DDS coding practices are unlikely to explain the increase in DDS clients with autism.

Prevalence of autism spectrum disorders - Autism and Developmental Disabilities Monitoring Network, United States, 2006.
Autism and Developmental Disabilities Monitoring Network Surveillance Year 2006 Principal Investigators; Centers for Disease Control and Prevention (CDC).
MMWR Surveill Summ. 2009 Dec 18;58(10):1-20.

To analyze changes in identified autism spectrum disorder (ASD) prevalence, the Centers for Disease Control and Prevention (CDC) compare their 2006 and 2002 collected data for children at age 8. Their results indicate an increased prevalence of identified ASDs among U.S. children aged 8 years, and underscore the need to regard ASDs as an urgent public health concern.

Social demographic change and autism.
Liu K, Zerubavel N, Bearman P.
Demography. 2010 May;47(2):327-43.

The authors set out to investigate the relationship between autism and parental age at child's birth. Along the way, they find that a demographic eye on the rising prevalence of autism leads to three major discoveries. First, the estimated heritability of autism has been dramatically overstated. Second, heritability estimates can change over remarkably short periods of time because of increases in germ cell mutations. Third, social demographic change can yield genetic changes that, at the population level, combine to contribute to the increased prevalence of autism.

Timing of increased autistic disorder cumulative incidence.
McDonald ME, Paul JF.
Environ Sci Technol. 2010 Mar 15;44(6):2112-8.

Using data from long-term studies, the authors find change-point years in which the cumulative incidence of autism first increases in each data set. They conclude that, while the debate about the nature of increasing autism continues, the potential for this increase to be real and involve exogenous environmental stressors exists.

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