Is the increase in autism due to delayed fatherhood? On September 5th, the LA Times described a study that found that fathers over 30 are much more at risk of having an autistic child than younger men. It is widely known that the prevalence of autism has been on the increase in recent years, but researchers don't know why. I looked at the General Social Survey and found evidence that the increase might be due, in part, to men waiting longer to become fathers. I looked at men ages 40-50, and in 1994, the mean age for first-time fatherhood was 25.8. By 2004, the average had risen to 27.2. This might not sound like much, but let's look at it another way. In 1994, 24% of men became fathers after age 29. In 2004, the percentage was 37. That is a 54% increase in only one decade in the number of men starting fatherhood later in life.

According to the team that conducted the study, the association between the father's older age and autism might be due to "spontaneous mutations in sperm-producing cells and alterations in genetic 'imprinting,' which controls the genes that are activated during development."