DEAR DOCTOR K: I am a 34-year-old woman married to a man more than 20 years my senior. Our first child, a son born four years ago, is autistic. I have heard that older fathers are more likely to have autistic children. Is this true?
DEAR READER: I am not an expert on autism. I have learned what I know from experts here at Harvard Medical School. No one knows the causes of autism, but today the apparent consensus is that they are biological – something a child is born with.
As to your question, I’m told that some research has shown that a child’s risk of developing autism does rise as the age of the child’s biological father rises. One study found that the risk was smallest for children of fathers younger than 20 and greatest for children of fathers older than 50. A man in his 40s, for example, was almost six times as likely to have an autistic child as a man age 20.
In this autism study, boys were more likely to develop autism than girls. But the risk for girls also increased as fathers got older.
Why would this be? One theory is that the genetic material in the sperm of older fathers has somehow become altered in harmful ways by mutations. Mutations change the shape of a gene – and of the protein the gene makes.
A newer theory doesn’t focus on the shape of genes. Instead, it speculates that the genes in the sperm of older fathers are shaped normally, but are inappropriately turned on or off.
Don’t misunderstand: The great majority of children born to older fathers are not autistic, or unhealthy in other ways. Nevertheless, since you already have one autistic child, you and your husband should discuss your concerns about another pregnancy with your doctor and a genetic counselor.