Older Dads More Likely to Have Autistic Grandchildren: Hereditary Underpinnings of Autism

If you fathered children when you were older, your grandchildren may have an increased risk of autism. A new Swedish study found that men who had a child at the age of 50 or older were more likely to have a grandchild with the condition.

The findings, published in the journal JAMA Psychiatry, examined data from Sweden's national registries and compared about 6,000 people with autism to about 31,000 people without the condition. In particular, they looked at the age of each person's maternal and paternal grandfather and then examined the time of the individual's birth.

The link that the researchers found between the age of an individual's grandfather and their likelihood of their developing autism was significant. Men who were 50 or older when they fathered their children were 79 percent more likely to have a grandchild with autism than men who fathered a child when they were in their 20s. The findings hint strongly at the genetic underpinnings of this particular condition.

"We tend to think in terms of the here and now when we talk about the effect of the environment on our genome," said the co-author of the study, Avi Reichenberg, in an interview with Health Day. "For the first time in psychiatry, we show that your father's and grandfather's lifestyle choices can affect you."

So why would an older grandfather affect a child? It's possible that mutations lying within sperm cells could be the cause. Since sperm cells undergo division throughout a person's lifespan, each new division opens itself up for creating errors in the genome. While some of these mutations don't appear in a man's child, they may accumulate or emerge in his grandchild.

Yet the researchers were quick to note that just because there was an increase in risk, it doesn't mean that a child would definitely develop the condition. "Although there was a statistically significant increase in the incidence of autism in families with older grandparents, it must be remembered that autism was still extremely infrequent even in families with the oldest grandparents," said Andrew Adesman, one of the researchers, in an interview with Health Day. "Thus, older parents and grandparents should not be unduly worried."

The study could help researchers better understand the condition and help create tests that could pinpoint a child's odds for developing autism. This could allow doctors to treat the condition early and eventually lead to better therapy.