Is parental age related to autism?
According to the most recent estimates, about 6 in every 1,000 children are born with Autism Spectrum Disorders, and about 2 in every 1,000 are born with full-blown autism. Throughout the 1990s and 2000s, the number of reported cases in the U.S. and Canada has steadily increased. While this increase is partially attributable to better diagnostic practices, some medical experts have theorized that increased rates of autism have to do with parental age, in particular the fact that many parents are now waiting longer to have children.
Until recently, researchers looking into possible connections between parental age and autism have found mostly mixed results. But now, a new study conducted at the University of California begins to confirm what many experts have long suspected.
The results are complicated, but to put it simply, the study writers find that “women’s risk for delivering a child who develops autism increases throughout their reproductive years whereas father’s age confers increased risk for autism when mothers are <30.” In other words, the risk of autism goes up as the mother ages. As the father ages, the risk of autism stays the same or doesn’t significantly increase unless the mother is below the age of 30.
Some more specific results:
- Compared with women under the age of 25, women over 40 are 77% more likely to have a child with autism.
- Compared with women aged 25 to 29, women over 40 are 51% more likely to have a child with autism; women aged 35 to 39 are 31% more likely; women aged 30 to 34 are 12% more likely; and women under 25 are 14% less likely.
- Compared with men between the ages of 25 and 29, men over 40 are twice as likely to have a child with autism, but only when the mother is under 25.
Possible causes
The theories regarding the causes of autism are complicated and quite technical, but there are a few basic issues that many researchers say may explain the correlation between autism and advanced parental age.
The most important factor is genetics. Unlike some disorders, autism is not carried on a single gene. Rather, it comes from the interactions of a whole network of genes, which explains why there’s such a broad and diverse spectrum of autism disorders. As parents age, it becomes more and more likely that their sperm and eggs will contain tiny abnormalities that result in mutations. It may be that the types of abnormalities that typically show up in aged reproductive cells happen to lead to autism-related mutations at a high frequency.
Also, it’s thought that people with autism spectrum disorders who have children tend to have them at a later age. This is simply a result of the fact that people with autism often have social difficulties, meaning that they don’t find partners and have children until relatively later in life.
Meanwhile, older parents tend to be better educated both in general and regarding autism in particular. As a result, these parents are more likely than younger parents to recognize when a child shows signs of autism and to seek a medical diagnosis.
What this means for parents
The researchers who conducted the University of California study emphasize that this information should not discourage parents in the 35 to 45 age range from having children. As study writer Janie Shelton notes, “It would be premature to tell older moms not to have a child. It could be the risk is associated with an exposure, and avoiding the exposure would be more important than not having kids at age 40.”
In other words, until we have a clearer idea of what causes autism, it would be unreasonable to say that older men and women should avoid having children. It could be that there are very specific environmental or genetic factors that cause older parents to have autistic children at higher rates, and age might only be a tiny part of the puzzle.
- Staff -
Image courtesy of D. Sharon Pruitt via Flickr