Two recent, separate publications identified regions with higher than expected numbers of autism cases — or clusters — in California. Using data collected by the California Department of Developmental Services (DDS) on 2.5 million births including almost 10,000 autism cases from 1996-2000, investigators at UC Davis uncovered several clusters of elevated risk for autism. Autism Speaks, the nation’s largest autism science and advocacy organization, reviewed these studies and found that the majority of these clusters were found to be strongly associated with higher parental education and, to a lesser extent, with parents of older ages. It is thought that parents with higher levels of education may have better access to the regional diagnostic and service centers in California, as the DDS relies on parents actively seeking services. Thus the distribution of cases is likely influenced by proximity to specialty research and service centers.
However, demographic factors, alone, may not explain the increased numbers of cases in these clusters. The authors propose that other factors, including environmental exposures, may play a role but warrant further investigation to understand their contribution to autism etiology.
“Examination of clusters can help us understand the factors that have led to in increase in autism prevalence over time,” said Autism Speaks’ Chief Science Officer, Geraldine Dawson, Ph.D.
Similar to the UC Davis study, a second study using data collected by the California DDS, which was conducted by investigators from Columbia University identified a significant cluster of increased risk for autism as well as a set of lower risk clusters in and around Northern Los Angeles. However, rather than looking at incidence of cases by DDS Regional Center catchment area, Mazumdar et. al. examined more than 11,500 autism cases among four million births by place of birth. This approach was used to avoid potential bias caused by parents moving to neighborhoods that improve access to specialty autism services.
“Our paper is different,” Columbia University co-author Peter Bearman, Ph.D. said. “It identifies a large and stable primary cluster for autism based on residence at birth that is observed over many years and which crosses over regional center boundaries.”
The primary cluster accounted for approximately 3 percent of new autism cases in California each year from 1993-2000. While the primary cluster was found to be in an area of higher socioeconomic status than comparison regions, this factor did not fully account for the increased cases of autism in this region.
“Our findings point strongly to the idea that a local process is associated with the increased risk of autism. Such a local process could be either an environmental factor or a social influence factor, or both,” noted Bearman.
Both publications add to the growing body of evidence suggesting that the distribution of autism cases differs across different regions. While the exact causes of the clustering in California are unknown, ongoing studies exploring environmental exposures and social factors will be useful in providing answers.
Autism is a complex neurobiological disorder that inhibits a person’s ability to communicate and develop social relationships, and is often accompanied by behavioral challenges. Autism spectrum disorders are diagnosed in one in 110 children in the United States, affecting four times as many boys as girls. The prevalence of autism increased 57 percent from 2002 to 2006. The Centers for Disease Control and Prevention have called autism a national public health crisis whose cause and cure remain unknown.
About Autism Speaks
Autism Speaks is the nation’s largest autism science and advocacy organization. Since its inception only five short years ago, Autism Speaks has made enormous strides, committing over $131 million to research and developing innovative new resources for families through 2014. The organization is dedicated to funding research into the causes, prevention, treatments and a cure for autism; increasing awareness of autism spectrum disorders; and advocating for the needs of individuals with autism and their families. In addition to funding research, Autism Speaks also supports the Autism Treatment Network, Autism Genetic Resource Exchange and several other scientific and clinical programs. Notable awareness initiatives include the establishment of the annual United Nations-sanctioned World Autism Awareness Day on April 2 and an award-winning “Learn the Signs” campaign with the Ad Council which has received over $200 million in donated media. Autism Speaks’ family resources include the Autism Video Glossary, a 100 Day Kit for newly-diagnosed families, a School Community Tool Kit, a community grant program and much more. Autism Speaks has played a critical role in securing federal legislation to advance the government’s response to autism, and has successfully advocated for insurance reform to cover behavioral treatments. Each year Walk Now for Autism Speaks events are held in more than 80 cities across North America. To learn more about Autism Speaks, please visit www.autismspeaks.org.
About the Co-Founders
Autism Speaks was founded in February 2005 by Suzanne and Bob Wright, the grandparents of a child with autism. Bob Wright is Senior Advisor at Lee Equity Partners and served as vice chairman, General Electric, and chief executive officer of NBC and NBC Universal for more than twenty years. He also serves on the boards of the Polo Ralph Lauren Corporation, RAND Corporation and the New York Presbyterian Hospital. Suzanne Wright has an extensive history of active involvement in community and philanthropic endeavors, mostly directed toward helping children. She serves on the boards of several non-profit organizations and is a Trustee Emeritus of Sarah Lawrence College, her alma mater. In 2008, the Wrights were named to the Time 100 list of the most influential people in the world for their commitment to global autism advocacy.