Men Who Have Children Later May Pass Increased Risk of Autism to Grandchildren
Previous research has found that men who have children when they are older may be more likely to pass on gene mutations that lead to autism spectrum disorder. However, in a first, a team of researchers has found that link can be traced across generations. They found that men who had children when they were older tended to have grandchildren with autism. That meant that they passed on mutations that often had no effect on their children, but whose effects built up with time.
According to Reuters, the researchers from Australia, Sweden and the United Kingdom performed their study by analyzing data from a Swedish registry. They compared 5,936 people with autism, with 30,923 healthy controls. All of the participants had been born in Sweden after 1932. The researchers factored in the age of each person's grandfathers, on both their paternal and maternal sides, and recorded any psychiatric diagnoses.
The study revealed that men who had daughters after the age of 50 were 1.79 times more likely to have grandchildren with autism than men who has children between the ages of 20 and 24. The risk for men who had sons in advanced age was 1.67 times higher.
Previous research has indicated that men's age when conceiving is the single greatest risk factor for autism spectrum disorder. That may help to account for why the autism rate has increased in recent years. According to ABC News, 1 in 50 schoolchildren are believed to have autism spectrum disorder, a rise over the Centers for Disease Control and Prevention's last estimate of 1 in 88. In Europe, it is believed that 1 in 100 children have autism spectrum disorder.
It is not known why such a link would exist, though researchers believe that some of the answer may lie in the differences in reproduction across gender. In women, reproductive cells, with which she is born, divide 24 times. Men must continue producing reproductive cells throughout his life. By the age of 20, men's reproductive cells have undergone 200 divisions. Each division raises the risk of mutations.
In addition, autism spectrum disorder is thought to have environmental, as well as genetic, links. It is possible that older fathers may have had more exposure to environmental pollutants that may give rise to autism spectrum disorder as well.
However, researchers do not believe that older parents should be discouraged from having children. Even though the risk is increased, they note that it is still quite low. In addition, the data was not obtained in a laboratory, so it is still correlational rather than causational.
The study was published in the journal JAMA Psychiatry.