Monday, January 23, 2012

Timing of Increased Autistic Disorder Cumulative Incidence

Timing of Increased Autistic Disorder Cumulative Incidence

Michael E. McDonald* and John F. Paul
National Health and Environmental Effects Research Laboratory, U.S. Environmental Protection Agency, MD-B343-06, Research Triangle Park, North Carolina 27711
Environ. Sci. Technol.201044 (6), pp 2112–2118
DOI: 10.1021/es902057k
Publication Date (Web): February 16, 2010
Copyright © 2010 American Chemical Society
* Corresponding author phone: (919) 541-7973; fax: (919) 541-2581; e-mail:


Autistic disorder (AD) is a severe neurodevelopmental disorder typically identified in early childhood. Both genetic and environmental factors are implicated in its etiology. The number of individuals identified as having autism has increased dramatically in recent years, but whether some proportion of this increase is real is unknown. If real, susceptible populations may have exposure to controllable exogenous stressors. Using literature AD data from long-term (10-year) studies, we determined cumulative incidence of AD for each cohort within each study. These data for each study were examined for a changepoint year in which the AD cumulative incidence first increased. We used data sets from Denmark, California, Japan, and a worldwide composite of studies. In the Danish, California, and worldwide data sets, we found that an increase in AD cumulative incidence began about 1988−1989. The Japanese study (1988−1996) had AD cumulative incidence increasing continuously, and no changepoint year could be calculated. Although the debate about the nature of increasing autism continues, the potential for this increase to be real and involve exogenous environmental stressors exists. The timing of an increase in autism incidence may help in screening for potential candidate environmental stressors.

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