New research suggests that children of older fathers are at a higher risk of having autism. Mt. Sinai School of Medicine epidemiologist Avi Reichenberg and his colleagues compared more than 300,000 parent-child records, and found that men older than 40 were nearly six times more likely to have children with autism than fathers under 30 years old.

For men over 40, this translates to a risk of 32 autistic children out of 10,000. For fathers under 30, the risk is 6 out of 10,000. Reichenberg stresses that the research shows only an increased risk and not a guarantee of autism in children. Reichenberg says that they did not find any link between mothers' ages and autism in their children.

Autism is a developmental disorder where children have trouble communicating, find it difficult to socialize with peers, and exhibit repetitious behaviors. According to the Autism Society of America, the disorder is known to affect as many as 1.5 million Americans.

Reichenberg's team sifted through Israeli draft records from the 1980s, which contained information on all 17-year-old Israelis whether or not they would be selected for service. According to the study, virtually all autistic children are already diagnosed by the time they reach the age of 17, and this information would be reported in the records. Most of the record data also contained paternal and maternal age.

"The next step is, of course, to try and understand what this means," Reichenberg says. He says it may be due to the quality of older men's sperm. "One possibility is that older fathers have a higher risk of errors in their genetic material, and these errors might be transmitted to their kids."

He says that this may change the way men think about age. "For many years we knew that females had biological clocks ... this study and other studies suggest that there may be biological clocks for men as well," he says.

Reichenberg says there are no immediate clinical implications for this research. "We would not tell fathers to not have babies after the age of 40," he says. Researchers will use this information in their search for genes related to autism and to gain a better understanding of how age affects genetic material.