A father's older age has already been linked to a risk for autism in children in past studies. Now researchers have turned their attention to grandfathers.
A recent study found that the age of grandfathers when they had their children may be linked to the risk of autism in their children's children.
Men over age 50 when they had their children were slightly more likely to have a child born with autism than men who were age 20 to 24 when they had their children.
The study, led by Emma M. Frans, MSc, of Department of Medical Epidemiology and Biostatistics at the Karolinska Institutet in Stockholm, Sweden, looked at whether the age of a child's grandfather was linked to the child's risk of having autism.
The authors first gathered data on the parents' ages when children were born from all children born in Sweden since 1932. The researchers were able to find 90 percent of this data and then narrowed it to those for whom they had the grandfather's age at his child's birth.
Overall, the researchers located 5,936 children with autism and 30,923 children without autism to include in the study. These were all the individuals for whom the researchers knew the parent's age when the child was born and the grandfathers' ages when those parents were born.
The researchers found a link between the age of the grandfathers when their children were born and the risk of autism in their grandchildren.
For example, men who were aged 50 or older when they had their daughter were 79 percent more likely to have a grandchild with autism compared to men who were aged 20 to 24 when they had their daughters.
If men had a son while aged 50 or over, they were 67 percent more likely to have a grandchild with autism than if they had been aged 20 to 24 when they had their son.
These findings took into account the year the grandchild was born, the sex of the child, a family history of psychiatric disorders, the age of the other grandchild's parent, the highest level of education in the family and where the family lived.
"Advanced grandparental age was associated with increased risk of autism, suggesting that risk of autism could develop over generations," the authors wrote. "The results are consistent with mutations and/or epigenetic alterations associated with advancing paternal age."
"Epigenetic alterations" refers to changes that can happen in individuals' genes after they are born, whether as a result of age or environmental exposures or other factors.
While individuals cannot change the fact of their parents' ages when they are born, being aware of a higher risk of autism as a result of older fathers and grandfathers can help researchers better understand which children are at a higher risk of being born with autism.
The study was published March 19 in the journal JAMA Psychiatry. The research was funded by the Swedish Research Council, the Swedish Council for Working Life and Social Research and the Karolinska Institutet. The authors declared no conflicts of interest.