Older Dads More Likely to Have Autistic Grandkid?
Men who became dads at age 50 or older had higher odds for a grandchild with the disorder
The new research was published on the same day that the U.S. Centers for Disease Control and Prevention announced that one in every 50 U.S. school children now has an autism spectrum disorder -- up from the 2007 estimate of 1 in 88. The CDC says improved detection and diagnosis are probably responsible for most of that increase.
In the new study, researchers looked at data from Sweden's national registries and compared about 6,000 people with autism to about 31,000 people without the condition. They looked at the age of each person's maternal and paternal grandfather at the time of the individual's birth.
The link between autism and a grandfather's age was significant, the team said, and pointed to the genetic underpinnings of the condition. They noted that previous studies have found a link between older fathers and rising odds for autism in their children, such that men who have a child when age 50 or older have a double the risk of having a child with the disorder.
Mutations lying within sperm cells might be the culprit, the researchers said. Sperm cells undergo division throughout the lifespan, and with each new division errors in the genome can occur. Some of these mutations might remain "silent" in a man's child but then accumulate or re-emerge to cause problems in future generations.
"These findings add further support to the belief that subtle genetic abnormalities -- defects that were previously undetectable -- are likely responsible for some cases of autism," Adesman said.
This type of research might lead to tests that could pinpoint a child's odds for an autism spectrum disorder, he added. "Newer molecular genetic laboratory tests will increasingly allow scientists and doctors to find atypical parts of chromosomes that put a child at increased risk for an autism spectrum disorder," Adesman said.
Another expert said the new study could raise as many questions as it answers.
Although the researchers offer theories as to how a man's age might affect the risk for autism in his descendants, "more research is needed to better understand how this occurs," said Alycia Halladay, senior director for environmental and clinical sciences at the advocacy group Autism Speaks. "For example, it could be through modifications of DNA, or it could result from environmental factors modifying how DNA is expressed," she said.
"This study is important because it utilizes rich datasets with health record information," Halladay added. "This approach can open the door for future work on genetic and environmental factors associated with [autism spectrum disorders]."