Welcome to the State of California 


Date: 10/5/2009 

Number: 09-87 

Contact: Al Lundeen - (916) 440-7259 


Reviewing a larger population than in any other study of its kind, the California Department of Public Health (CDPH) has found that as parents age their risk of giving birth to a child with autism increases modestly.

Published in the American Journal of Epidemiology, the new CDPH study shows that for each 10-year increase in a mother’s age, the risk of autism increased by about 38 percent.  For each 10-year increase in a father’s age, the risk of autism increased by about 22 percent.

In the past, experts agreed that about 1 in 160 young children in the United States have an autism spectrum disorder. Recent data, however, from two government studies, the federal government's 2007 National Survey of Children's Health, and the Centers for Disease Control and Prevention, suggest that the frequency of these disorders may be as common as 1 in 100 children.

“The causes of autism remain largely unknown,” said Dr. Mark Horton, director of CDPH. “This study provides clues to further our understanding of this disease. Additional research is needed to learn more about how parental age is linked to autism.”

Using data from the California Department of Developmental Services (DDS), researchers examined birth certificate records for 20,701 children with autism and 6,505,555 children without autism born from 1989 to 2002. The increased risk of autism was greatest among first-born children and declined among second-born and later-born children. In addition, the link between parental age and autism was not due to other factors such as education, sex, race or ethnicity.

“This study adds another piece of information to the body of research on autism,” said Dr. Linda Rudolph, deputy director of CDPH, Center for Chronic Disease Prevention and Health Promotion. “We do not know why the risk for giving birth to a child who will be diagnosed with autism seems to increase modestly as parents age. There are still more questions than answers; there is far more work to be done to better understand autism and autistism spectrum disorders.”

Once considered rare, autism and autistism spectrum disorders (ASD) now are more prevalent than Type I diabetes, Down syndrome or childhood cancer. People who have autism now outnumber people with cerebral palsy, and are soon projected to exceed those diagnosed with epilepsy. Currently there are more than 38,000 people in California receiving services from the state’s Department of Developmental Services for autism and ASD, growth that has averaged 13.4 percent annually since 2002.

Autism is a neurological or brain disorder that profoundly affects a person’s ability to communicate, form relationships with others, and respond appropriately to the environment. Children who have the neurodevelopmental disorder associated with autism generally show little interest in other people and fail to learn from their natural environments as successfully as other children. Although some children with autism can develop typical or advanced skills, the majority exhibit a wide range of behavioral, cognitive, and emotional challenges. 

Parents should consult their health care provider if developmental delays are suspected and also contact their local Regional Center which serve persons with developmental disabilities and their families. 

Click here for additional information about autism and DDS resources.

The study is called “Risk of Autism and Increasing Maternal and Paternal Age in a Large North American Population.” 

Last modified on: 10/5/2009 1:49 PM