As we noted in an earlier post, we’re highlighting some recent autism-related research findings this month.
You may already know that autism has been linked to increased maternal and paternal age, but a very interesting Swedish study was just published in the Journal of the American Medical Association, climbing even further back in the family tree.
As it turns out, the age of a child’s grandfather also contributes to a child’s relative risk of developing autism. Men who were over 50 when their children were born were more likely to have a grandchild with autism. Older men with daughters were 1.79 times more likely to have a grandchild with autism, and men who had sons when they were 50 or older were 1.67 times more likely to have a grandchild with autism.
The mechanism appears to be related to the fact that cellular mutations in the reproductive cells increase with age. For example, the male germ cells of a 20-year-old man have undergone 200 divisions, and by 40, they’ve divided 660 times. That’s a lot of opportunity for what scientists call “copy errors”. As an analogy, imagine making a copy on a piece of paper, then copying that copy, then copying the third copy, etc. Now do it 660 times. The later copies don’t quite like the original, do they? Obviously, our bodies do a much better job of copying our genetic information than a copy machine, but nonetheless, the risk of genetic mutations rises with age.
No one investigated whether the grandfathers themselves had been diagnosed with autism or other related disorders. The researchers noted that it is possible that men with psychiatric disorders may be more likely to become fathers at an older age. However, other research has controlled for the effects of mental illness and still found the link to paternal age. This suggests that the real key is in the reproductive cells, and all that copying.
The highest risk, as you can imagine, was for children born to older parents, who themselves had older parents. However, the contribution of grandpaternal age was independent of the age of the child’s parents.
Does this mean that older parents should not have children? Of course not! Many factors contribute to the risk of developing autism, most of which are not yet fully understood. The study’s authors state, “Older men should not be discouraged to have children based on these findings, but the results may be important in understanding the mechanism behind childhood autism and other psychiatric and neurodevelopmental disorders” (Frans, et al., 2013).
Remember, please help spread autism awareness this month, and throughout the year! The more you know, the more you can help.
—Lori J. Warner, Ph.D., LP, BCBA-D, Director, HOPE Center