New research indicates that a grandfather's age may be a risk factor in autism development, according to a study from investigators at Sweden's Karolinska Institute.
This is the first study to suggest that the risk for autism "may accumulate" over generations.
In a statement about the research, study coauthor Dr. Avi Reichenberg said, "For the first time in psychiatry, we show that your father's and grandfather's lifestyle choices can affect you."
Dr. Reichenberg added that this does not mean that you should not have children "if your father was old when he had you." While the risk is higher, "it is still small," he said.
These findings are important, however, because they help scientists understand how autism may develop, the researcher noted. The study appears in the March 20 JAMA Psychiatry.
The Karolinska study is based on information from Swedish national registers.
Investigators identified nearly 6,000 individuals with autism and more than 30,000 "healthy controls" born in Sweden since 1932.
They then accumulated data on each individual grandfather's age when he fathered a child, along with details of any psychiatric diagnosis.
The provocative finding: The risk of autism in a grandchild rose depending how old the grandfather's was when he fathered his own son or daughter.
For instance, men who fathered a daughter when they were over age 50 were 1.79 times more likely than were younger men to have a grandchild with autism.
Similarly, men who fathered a son when they were 50 or older were 1.67 times more apt to have a grandchild with autism, compared with men who fathered a child when they were 20 to 24.
Interestingly, this news comes just days after another report earlier this week indicated that in the United States about one in 50 school age children has autism.
That report was based on figures from a U.S. Centers for Disease Control and Prevention survey that suggested that there are at least one million autistic children, ABC News.com reported.
Autism is a developmental disorder that appears in early childhood— typically before age three. It affects a child's brain development and leads to impaired social functioning, interactions with others, and communication.
While the new stats seem profoundly disturbing, experts agree that these findings alone do not mean that older parents should be discouraged from having children.
Lori Warner, director of the HOPE Center for Autism at Beaumont Hospitals in Michigan, told ABC News that while it is wise to know your background, "that shouldn't be a deciding factor".
Of course, more research is needed. In the meantime, if you have any concerns at all, talk to your health care provider.
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