Older fathers linked to higher autism risk

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REYKJAVIK, Iceland, Aug. 23 (UPI) -- Older men's sperm may be "mutational bombs," because men's genetic mutations increase as they age, Icelandic and U.S. researchers say.

Dr. Kari Stefansson, chief executive officer of deCODE Genetics in Reykjavik, Iceland, said the study found the number of "de novo" or new genetic mutations passed to children via sperm increases with every year of a man's age at the time of conception, WebMD reported. In addition, fathers pass along a greater number of these mutation to their children than do mothers, Stefansson said.

The study, published in the journal Nature, found the number of de novo mutations in children increases by two for every year of the father's age, while the whole amount doubles every 16.5 years.

For example, a 36-year-old man passes along twice as many mutations in his sperm to his children, compared to a 20-year-old man, the study said.

Earlier studies linked these mutations to autism and schizophrenia and other developmental disorders, Stefansson said.

"We have in many ways been led a bit astray when it comes to the impact of the age of parents," Stefansson said. "As a society, we have been focused on the age of the mother as being detrimental, but probably the age of the father is more dangerous."

The researchers compared mutation rates in 78 Icelandic parent-offspring trios -- 44 of the children have autism spectrum disorder and 21 have schizophrenia. Not only did the novo mutations increase by two for each year of the father's age, but nearly all variation -- 97 percent -- in the number of these mutations was attributable to paternal age, Stefansson said.