In a new study of more than 9,500 children in Denmark who had been diagnosed with an autism spectrum disorder, researchers found that children born to a parent over the age of 35 had a higher risk of developing autism. Interestingly, the data also showed that the risk is the same whether both parents are older or only one of them is.
Erik Thorlund Parner, who led the study at the University of Aarhus School of Public Health, tells Reuters Health that if genetic problems arising from older sperm or eggs explain the results, then having both an older sperm and an older egg together should add up to an even higher risk of autism for the child. But this study raises questions as to why older parents are more likely to have children with autism due to the fact that two older parents did not create a higher risk than just one.
The data from this study showed that children had a 28 percent higher risk of being diagnosed on the spectrum if they were born to fathers in their late thirties, as opposed to fathers who were under the age of 35. Likewise, mothers who were over the age of 35 were 21 to 27 percent more likely to have children who develop autism. These results were regardless of the age of the other partner.
The odds of an autism diagnosis increased even more if either parent was over the age of 40: children with fathers over 40 had a 37 to 55 percent greater risk, while mothers over 40 saw a 28 to 65 percent increased risk in their children.
Parner tells Reuters that these results were surprising. “I don’t believe that one can yet say anything conclusive about whether (having an) older parent is biologically related to autism.”
An even larger analysis of autism and parental age is being planned by Parner and his fellow researchers, using data from six different countries.
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