Gaining Ground on Autism
Clustering of Autism in California 1993-2001
This spatial clustering map shows a small area in California, North of Los Angeles, where there is a cluster of children born with autism. The children born in this part of the state are at four times greater risk for autism than children living in other parts of California. The risk is still present after adjusting for sex, birth order (firstborn or not), prenatal insurance status, preterm birth status, poor presentation at birth, low birth weight status, parental age, education, and race. The cluster consists of three separate regions centered around Santa Monica, Alhambra and North Hollywood. The area centered around North Hollywood is by far the largest. It has an approximate radius of 6 miles and is bounded by the South Central Regional Center to the South, the North Los Angeles regional center to the North, and Interstate 5 to the West..The prevalence of autism in the United States has increased significantly over the past twenty years. While reasons for this increase remain elusive, the rise in autism rates continues to generate debate among scientist, caregivers and the public. Dr. Peter Bearman at Columbia University, a researcher in the Common Fund's Pioneer Award program, moves us one step closer to understanding why autism is increasing in California and identifying how local environmental and social factors may play a key role.
Using information from state birth records and case records of patients affiliated with the California Department of Health Services, Dr. Bearman and colleagues estimate that approximately 25 percent of the increased prevalence of autism observed in California between 1992 and 2005 is due to changes in how autism is diagnosed. The data also indicate that advanced maternal age poses a larger risk for autism than advanced paternal age. Because the effect of parental age on the rate of autism varies from year to year, the researchers speculate that variations in environmental or other factors may be associated with the extent of risk that can be attributed to parental age (King and Bearman, 2009; King et al., 2009).
Dr. Bearman and colleagues recently published that there are certain geographical areas of California where babies are more likely to develop autism. The finding of localized "clusters"; of autism suggests that environmental toxins or social factors such as increased public awareness and local advocacy may play a role. Using a spatial structure mapping technique, the researchers identified the high-risk clusters of autism based on residence at birth in California for children born from 1993 to 2001. Children born in a primary cluster have a four times greater risk for autism than children living in other parts of the state. While the study does not attempt to identify specific causes for autism, it does suggest that autism triggers could be environmental or social factors or both.
Read more: http://news.columbia.edu/research/1906
References
- King M and Bearman P. Diagnostic change and the increased prevalence of autism. Int J Epidemiol. 2009 Oct;38(5):1224-1234. PMID: 19737791.
- King MD, Fountain C, Dakhlallah, D and Bearman, P. Estimated autism risk and older reproductive age. Amer J Pub Health 2009 Sept;99(9):1673-1679. PMID: 19608957.
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