Researchers have found a link between a grandfather’s age and an increased risk for autism in his grandchildren. Emma Frans, the lead author of the study, reviewed data with her colleagues on births in Sweden beginning in 1932. Among the tens of thousands of births, the database they used had information about grandparental age for nearly 6,000 autism cases and for almost 31,000 controls (families with no autistic children).
The study showed that grandfathers who had a daughter when they were 50 or older were 1.79 times more likely to have an autistic grandchild. If they had a son at age 50 or order, they were 1.67 times more likely to have an autistic grandchild.
The study also found that the age-related increase in autism risk was independent of the age of the autistic child’s own parents. Other studies, however, have identified a link between older parental age (particularly for fathers) and autism risk.
The researchers pointed to other studies suggesting that new genetic mutations occurring over the father’s lifetime might pass to offspring and be linked to autism. If this is possible for dad, then it’s possible for grandpa to have made a contribution to any autism-related gene changes.
If environmental factors are interacting with these genes in the risk for autism, then the findings seem to suggest that we need to not only look at current environmental factors, but also go back at least two generations.
“Considering our finding linking grandpaternal age and risk of schizophrenia, we propose that a proportion of age-related de novo mutations are phenotypically silent in the offspring, but can still influence risk of autism in subsequent generations, perhaps via the interaction with other susceptibility factors,” said the researchers.