When it comes to autism risk theories, we've pretty much heard it all. The developmental disorder has been tied to a seemingly endless range of factors, with everything from low birth weight to pregnancy stress being suggested as possible causes. But this week, a study funded by Autism Speaks has thrown an entirely new one at us, and honestly, the results are more than a little surprising. In research published this week in the journal Molecular Psychiatry, psychologists found, among other things, that autism risks increase for kids born to teen moms or parents with wide age gaps. And this was no small study, either: it's been noted as the largest multinational study on the parental age connection to date.
"Though we've seen research on autism and parental age before, this study is like no other," study co-author and Autism Speaks director of public research Michael Rosanoff said in a press release Tuesday. "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."
To do so, a team of researchers combed through data from more than 5.7 million kids — 30,000 of whom were diagnosed with autism and all of whom were born between the years 1985 and 2004. Researchers then followed up with each child's development between the years 2004 and 2009 by scanning national health records to see whether or not they had been diagnosed with autism.
Here are the most eye-opening parts of what they discovered:
- Kids born to dads 50 and over were 66 percent more likely to develop autism than kids born to dads in their 20s. (In contrast, autism rates were 28 percent higher for kids born to dads who were in their 40s versus 20s.)
- Kids born to teen moms were 18 percent more likely to develop autism than those born to moms in their 20s.
- Kids born to moms in their 40s were 15 percent more likely to develop autism than kids born to moms in their 20s.
- Autism rates rose even higher when both parents were older.
- Autism rates also rose the wider the gap was between each parent's age. What's more, these rates were the highest when dads were between 35 and 44 years old and their partners were 10 or more years younger than them. Same went for moms in their 30s — rates rose when her partner was 10 or more years younger.
"After finding that paternal age, maternal age and parental-age gaps all influence autism risk independently, we calculated which aspect was most important," said Dr. Sven Sandin in the Autism Speaks press release. Sandin is a study co-author and medical epidemiologist at both the Icahn School of Medicine at Mount Sinai and Sweden’s Karolinska Institute. "It turned out to be parental age, though age gaps also contribute significantly."
Needless to say, all of this was pretty fascinating to researchers, who were not so surprised to see a correlation between older dads, but definitely surprised about the teen mom connection. As Rosanoff told Yahoo, there are lots of theories as to why a dad's older age plays a role in the autism diagnosis. (One of which is that "we accumulate mutations in sperm and egg cells as we age.) As for the teen mom correlation, well, that one's left scientists a bit stumped. But speaking to Yahoo, Rosanoff said that researchers do have one theory: a younger pregnancy might be "suboptimal" by nature, leading to less medical monitoring and higher health risks.
Now before you go freaking out about all of this (like I kind of just did), consider this: so much more research is still needed to be done to draw any definitive conclusions. While the new study raises lots of new correlations, it will take some time before researchers can fully explore the why. "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," Dr. Sandin assured. Plus, as Rosanoff told Yahoo, "Risk doesn’t mean cause. These are risk factors helping us to understand ideological pathways — but not a cause in itself."
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