Father’s Age Linked to Autism

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By Benedict Carey, The New York Times

Men, too, have a ticking biological clock. Scientists have found, older men are at risk of fathering a child that may develop autism or schizophrenia, compared to younger men.

The study, which was published in the science journal Nature, found that for complex developmental and psychiatric problems, the lion’s share of the genetic risk originates in the sperm, not the egg. The study found support for the argument that the surging rate of autism diagnoses over recent decades is attributable in part to the increasing average age of fathers, which could account for as many as 20 to 30 percent of cases. This risk was higher at age 35 than 25 and crept up with age.

The findings also counter the longstanding assumption that the age of the mother is the most important factor in determining the odds of a child having developmental problems. The research showed that the average child born to a 20-year-old father had 25 random mutations that could be traced to paternal genetic material. The number increased steadily by two mutations a year, reaching 65 mutations for offspring of 40-year-old men.  The average number of mutations coming from the mother’s side was 15, no matter her age.

Experts however said that the finding was hardly reason to forgo fatherhood later in life, though it might have some influence on reproductive decisions. The overall risk to a man in his 40s or older is in the range of 2 percent, at most, and there are other contributing biological factors that are entirely unknown.  

“You are going to have guys who look at this and say, ‘Oh no, you mean I have to have all my kids when I’m 20 and stupid?’ ” said Evan E. Eichler, a professor of genome sciences at the University of Washington in Seattle. “Well, of course not. You have to understand that the vast majority of these mutations have no consequences, and that there are tons of guys in their 50s who have healthy children.”

 (This article entitled “Father’s Age Linked to Autism and Schizophrenia” originally appeared in the New York Times on August 22, 2012 http://www.nytimes.com/2012/08/23/health/fathers-age-is-linked-to-risk-of-autism-and-schizophrenia.html?_r=1)