Paternal Age, de Novo Mutations and Autism Risk

Ted Schettler, MD, MPH
Science Director

A recent study of paternal age, de novo DNA mutations, and autism risk in Iceland, published in the journal Nature, has received considerable attention. The authors of the study found more de novo DNA mutations in children with autism and those mutations were largely traced to fathers rather than mothers. Increasing numbers of mutations were also associated with increasing paternal age. The authors wondered if recent increases in autism were largely attributable to the increasing age of fathers.

The New Yorker said, “What was surprising was how that news, which one of the study’s lead authors described as “sort of a little bit of our side story,” obscured the implications of the paper’s main findings—namely, that the genetic health of the species is now facing a serious threat.” Read more.  Important as this is, most reports have failed to comment on another observation in the paper.  The authors said this:

“There has been a recent transition of Icelanders from a rural agricultural to an urban industrial way of life, which engendered a rapid and sequential drop in the average age of fathers at conception from 34.9 years in 1900 to 27.9 years in 1980, followed by an equally swift climb back to 33.0 years in 2011, primarily owing to the effect of higher education and the increased use of contraception. On the basis of the fitted linear model, whereas individuals born in 1900 carried on average 73.7 de novo mutations, those born in 1980 carried on average only 59.7 such mutations (a decrease of 19.1%), and the mutational load of individuals born in 2011 has increased by 17.2% to 69.9. Demographic change of this kind and magnitude is not unique to Iceland, and it raises the question of whether the reported increase in ASD diagnosis lately is at least partially due to an increase in the average age of fathers at conception.”

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