The cause of autism is not completely understood, but several risk factors have been identified that are associated with its occurrence, including advanced age of both mothers and fathers. Now, a new study reveals that advanced age of grandparents may also predispose children to autism.
The study, published in JAMA Psychiatry, evaluated multiple generations of people born in Sweden since 1932. The researchers obtained parental age and grandparental age at the time of birth for nearly 6000 children with a diagnosis of autism and an additional 31,000 control cases. A significant association was found between older grandfathers and childhood autism. Men who fathered a daughter after the age of 50 were 1.79 times more likely to have a grandchild with autism, compared with men who fathered a child between the ages of 20 and 24. Men who fathered a son after the age of 50 were 1.67 times more likely to have a grandchild with autism.
The authors concluded that the risk of autism may develop over generations, owing to genetic mutations or alterations in male sperm cells that are passed on to offspring. Possibly, these alterations remain silent in the first generation of offspring, but will get passed on to future generations where they interact with other risk factors or environmental conditions until a disorder manifests itself.