Autism has been more commonly diagnosed in recent years, increasing from five in 10,000 children two decades ago to about 50 in 10,000 today. Researchers believe that this is at least partly due to increased awareness and more sensitive diagnostic criteria, but it may also reflect a true increase in incidence.

Autism is characterized by difficulties in social and language skills, and repetitive behavior patterns. Since older mothers and fathers are more likely to have children with certain brain abnormalities, some researchers have proposed that parental age may affect autism risk. But, until now, studies on the topic have been limited and their results mixed.

A new study in the September 2006 Archives of General Psychiatry found that older fathers were more likely to have children with autism spectrum disorder (ASD, autism and related disorders) than younger fathers.

About the Study

This study included 132,271 children born in Israel during the 1980s. When the children were 17 years old, they were assessed by the Israeli draft board, during which time any psychiatric conditions, including ASD, were recorded.

The draft board identified 110 cases of ASD among the participants, which corresponds to an incidence of 8.3 cases per 10,000 children. After adjusting for other factors potentially associated with autism, including year of birth, socioeconomic status (based on father’s education), and maternal age, the researchers found that paternal age was significantly associated with the risk of ASD. Specifically, men who were 40 years or older when their children were born were 5.75 times more likely to have children with ASD than men younger than 30. After adjusting for paternal age, the mother’s age was not associated with the risk of developing ASD.

This study was limited because the draft board did not distinguish between specific diagnoses of ASD, which includes autism, as well as related disorders such as Asperger syndrome . But the researchers believe that most of the participants had autism rather than other ASD diagnoses.

How Does This Affect You?

These findings suggest that children of older fathers may be at increased risk of developing autism and related disorders. The study could not determine why the father’s age was associated with autism risk, but the researchers propose that age-related genetic changes in the cells that make sperm may be involved.

Should parents consider the father’s age when deciding when or whether to have children? It’s too early to say. In considering the risks associated with being older parents, most of the attention has focused on the mother’s age. This study opens a new door, suggesting that the age of the father may also influence those risks.