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:

When I was in medical school, I spent a summer working with autistic children and will never forget the experience. The children seemed so distant from everyone -- others their own age, the health professionals around them and, of course, their parents. They were in worlds of their own. They often appeared happy in those worlds. But in failing to connect with people around them, from my perspective they were missing one of the most important parts of being alive -- in particular, the ability to receive love.

What was even more distressing was that theories about autism placed a lot of blame on the parents. How the parents interacted with the child was thought to have caused the autism. As a result, parents often had a layer of guilt placed on top of the unimaginable suffering of feeling that their child was lost to them.

In contrast, it seemed to me that these children were probably born different, and how their parents treated them had nothing to do with it.

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.

There are many things you can do to make your son's life as happy and healthy as possible. One of my colleagues at Harvard Medical School, Martha Herbert, M.D., has written a wonderful new book, "The Autism Revolution," about whole-body strategies for helping those with autism. You can find out more about it at my website, www.AskDoctorK.com.

(Dr. Komaroff is a physician and professor at Harvard Medical School. Go to his website to send questions and get additional information.)

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