The largest study of its kind on parental age and its link to autism has been completed and published in Molecular Psychiatry, and it may help us to understand the causes of the mysterious autism spectrum.
Ed Cara, writing for MedicalDaily, reports that by using the medical records of 5.7 million children in five countries, researchers believe they have found a significant link between the age of a child’s parents at birth and the later risk of developing an autism spectrum disorder (ASD).
“Though we’ve seen research on autism and parental age before, this study is like no other,” said study author and epidemiologist Dr. Michael Rosanoff in a press statement. “By linking national health registries across five countries, we created the world’s largest data set for research into autism’s risk factors. The size allowed us to look at the relationship between parents’ age and autism at a much higher resolution – under a microscope, if you will.”
The study included Denmark, Norway, Sweden, Israel, and Western Australia and observed the rates of autism of 5,766,794 children born between the years of 1985 to 2004. The result was that 30,902 children were diagnosed with ASD and researchers were able to find an observable tie between parental age and the possibility of developing autism.
The current data, when connected to earlier research, showed a strong connection to older fathers, with a 66% higher rate of autism among children with fathers aged 50 or older compared to children born to fathers in their 20s. There was a similar finding for women in their 40s, who were 15% more likely to have a child develop ASD than were younger mothers.
Teen parents had an 18% more likely to result in a child who would develop autism than moms in their 20s, a finding that had not been discovered in previous studies. Enough information was available for researchers to study whether large gaps between the ages of a mother and father, or having two older parents, could contribute to autism.
“The risk was highest when both parents were older, but the risk was also increased among disparately aged parents,” the authors wrote. These gaps (10 years or more) weren’t entirely explained by the age of one older parent alone, which suggests that these May-December romances have “other socio-economic (SES), genetic, and/or psychological characteristics that increase their risk of having children with ASD.”
The relationship between age and ASD has not been firmly proven, but scientists believe that the increased sperm and egg mutations among older parents may be a part of the link.
There may also be a social component to the link. Personality traits like shyness and aloofness, which often limit a person’s ability to handle cross-sex interactions, have been described for parents of kids with ASD. These same factors might determine at what age a person is able to establish a relationship with another person and have children, which creates yet another conundrum when making an association between parental age and risk of ASD.
Medical News Today’s James McIntosh says the researchers adjusted their findings to allow for the possible influence of the other parent’s age and controlled for other influences which were age-related that might influence the risk of ASD.
“After finding that paternal age, maternal age and parental age gaps all influence autism risk independently, we calculated which aspect was most important,” co-author Dr. Sven Sandin states. “It turned out to be parental age, though age gaps also contribute significantly.”
Other information about variables that could influence the findings were lacking, such as parental psychiatric history and obstetric complications like gestational diabetes mellitus.
The researchers involved in this study say the findings imply there could be multiple mechanisms involved that play a part in the link between parental age and the risk for ASD, which need to be further researched. What did result from the study was the understanding that parental age is a specific risk factor for autism, writes Angela Mulholland of Canada’s CTV News.
According to the Pew Research Center, older parents are becoming more common in the US and in Europe, says Amy Nordrum, reporting for the International Business Times. In the years between 1990 and 2008, births to women 35 and older grew from 9% to 14% of all births in the US. Teen births during this time dropped by 3 percentage points, making up 10% of all births in 2008.