A study published in the Archives of General Psychiatry found that men in their 40s are almost six times more likely to father children with autism spectrum disorders than men in their 20s. (There was no relationship between mother's ages and autism.)

"Maternal and paternal ages have been associated with other neurodevelopmental disorders and have been considered in some previous studies of autism spectrum disorders. Advancing maternal age increases the risk of chromosomal abnormalities, such as Down's syndrome, and has been associated with the risk of brain damage during pregnancy, dyslexia, and mental retardation of unknown cause."

Older men are more likely to father children with certain congenital disorders, including Apert's syndrome.

The authors of the study continued:

"Among the possible mechanisms for an effect of paternal age on autism spectrum disorders risk are point mutations or structural chromosomal aberrations in the father's germline, or imprinting, in which an allele inherited from the father suppresses the expression of the mother's allele and determines the expression of a particular gene.

Although our understanding of genetic imprinting is nascent, it merits consideration in autism. Imprinted genes play a key role in brain development, investigations of Turner's syndrome suggest a role for imprinted genes in language development and social functioning, and parent-of-origin effects have been reported in Angelman's syndrome and in at least some autism studies."