Research released today supports previous studies showing that older fathers are more likely than younger fathers to have a child with autism or schizophrenia due to random mutations that increase in number with age.
Though the connection between older dads and autism has been made before, this study is getting a lot of attention (a fancy “Breaking News” alert from the NY Times, for example) as it’s the first to look at how this effect increases year by year.“This study provides some of the first solid scientific evidence for a true increase in the condition” of autism, said Dr. Fred Volkmar, director of the Child Study Center at the Yale School of Medicine, speaking to the Times,“It is extremely well done and the sample meticulously characterized.”
Experts say that the overall risk (of having affected children) for a man in his 40s+ is still low in the 2% range, max, and that there are likely numerous other undiscovered biological factors in play. But this research does help support the argument that steeply rising rates in autism may at least be partly explained by an increase in older fathers–30% of cases could be due to older fathers.
Icelandic researchers looked at blood samples from 78 families, focusing on families in which the child developed autism or schizophrenia but the parents showed no signs of mental disorders themselves. (This helped isolate new mutations.)
The study found that kids of 20 year-old dads were found to have 25 random mutations that could be traced back to dad– the number of mutations increased each year by 2, so that kids of 40 year-old men had 65 of mutations. On average, moms contributed only 15 mutations regardless of her age.
According to the New York Times, “In the end, these kinds of mutations may account for 15 to 30 percent of cases of autism, and perhaps schizophrenia, some experts said. The remainder is likely a result of inherited genetic mutations and environmental factors that are the subjects of numerous studies.” Evan E. Eichler, a professor of genome sciences at the University of Washington in Seattle cautions that men should not take this all to mean that 20 is the time to have babies: “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.”
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