How much does dad’s age affect a child’s risk of autism?

While advanced maternal age has been linked with increased risk for child health problems, researchers are learning more about how paternal age may impact a child. Increasing paternal age has been linked with increased risks for some mental health disorders, including autism. These risks not only extend to the older father’s children, but also his grandchildren, one study says.

Several studies had identified preliminary findings that suggested increasing paternal age raises a child’s risk for mental health disorders, including attention deficit hyperactivity disorder (ADHD), bipolar disorder, autism, and schizophrenia. However, a 2014 study of live births in Sweden produced large-scale results that linked fathers 45 and older with increased risk of having a child with autism.

Researchers from Indiana University and the Karolinska Institutet in Stockholm, Sweden, conducted the study published in the April 2014 edition of the Journal of the American Medical Association (JAMA) Psychiatry. The researchers examined Sweden’s public health records from 1973-2001 to identify links between paternal age and risks for psychiatric and academic disorders. Results revealed fathers 45 and older were 3.5 times more likely than 24-year-old fathers to have a child with autism.

Another study published in the September 2006 edition of the JAMA Psychiatry journal suggested some potential links between advancing age and increased autism risk for a child. The study suggested de novo gene mutations in an older man’s sperm may be a risk factor. De novo mutations are those that occur following fertilization. Additionally, the cumulative effects of environmental toxin exposure may make DNA mutations more likely in men.

The average paternal age for a first child is on the rise. Married men in the United States are an average of 25.6 years old at the birth of their first child. Unmarried men with a child are the average age of 22.5, according to the U.S. Department of Health and Human Services. While research studies have not identified a definitive age where autism risk markedly increases, the study can provide considerations for older fathers considering conception with a partner.

Reviewed by Dr. Sara Connolly, January 2020