Parental age relating to autism is old news, but a study of 5.7 million is groundbreaking. The population-based cohort study from five countries (Denmark, Israel, Norway, Sweden and Western Australia) comprised 5,766,794 children born 1985–2004 and followed up to the end of 2004–2009.
The massive new study on autism risk has found elevations related to parental age – of both teen moms and older parents.
The study, published Wednesday in the journal Molecular Psychiatry, is the largest of its kind to ever look at the connection between parental age and autism risk.
“The size of the study speaks to the definitiveness of the findings,” says co-author Michael Rosanoff, director of public health research for Autism Speaks, the organization that funded the study. “We can now say confidently that advanced paternal and maternal age is a risk factor for autism.” Such findings are not new, he tells Yahoo Parenting, but this is by far the most sweeping of its kind.
It also turned up some new correlations: In addition to finding that autism rates were 66 percent higher among children born to dads over the age of 50 than those in their 20s (and 28 percent higher for dads in their 40s), researchers found rates were 18 percent higher with teen moms than those with moms in their 20s.
Also, autism rates were 15 percent higher in children born to mothers in their 40s — and higher than usual when there were wide gaps, of 10 years or more, between parents. That was especially true when dads were between 35 and 44 and their partners were at least a decade younger.
The increased risk on both sides of the age spectrum raise many questions, and Rosanoff says, “was intriguing to the investigators.”
Theories regarding the rise in autism risk for kids of older parents are pretty solid, he notes, explaining that one points to evidence that “we accumulate mutations in sperm and egg cells as we age.” Another hypothesis is that people who have children at advanced ages may do so because they themselves are “on the spectrum,” and may have social difficulties that made it tough for them to couple up and become parents for much of their early adult lives; in these cases, researchers theorize, there may be a genetic link to autism.
Looking at higher risk among teen moms, Rosanoff adds, scientists believe age itself might point to a “suboptimal pregnancy,” with less medical monitoring and higher health risks in general.
Still, there’s no reason for alarm, notes co-author Sven Sandin, a medical epidemiologist, in an Autism Speaks press release. “Although parental age is a risk factor for autism, it is important to remember that, overall, the majority of children born to older or younger parents will develop normally,” says the doctor, a medical epidemiologist with the Icahn School of Medicine at Mount Sinai, in New York, and Sweden’s Karolinska Institute.
The goal of the new study was to determine whether advancing maternal or paternal ages independently increase autism risk, and to what extent. But much more research is needed before any recommendations about birth and parenting age get officially changed, Rosanoff says.
“Risk doesn’t mean cause,” he notes. “These are risk factors helping us to understand ideological pathways — but not a cause in itself.”