There is evidence that fathering a child as an older man, increases the child’s risk of autism. The assumption has been that, as a man ages, there is a greater risk of mutation to the genes carried by the sperm cells.
However, here is an interesting alternative explanation:
Gratten and his colleagues developed a fifth model to test an alternate explanation for the paternal age effect: that men with a high genetic risk for autism — and who show autism traits — tend not to have children until they are older.
“We don’t think that this alternative mechanism, which is really just a hypothesis, accounts for all the risk on its own,” Gratten says. “Probably de novomutations contribute, and this mechanism may also contribute, and many others may as well.”
Still, this alternative hypothesis “makes sense for autism and seems quite likely for schizophrenia too,” says Bernie Devlin, professor of psychiatry at the University of Pittsburgh, who was not involved in the work. That’s because de novo mutations are believed to contribute to only a small fraction of risk for either condition. For autism, de novo mutations are thought to account for about 3 percent of risk.