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Older Dads and Greater Risk For Autism, Schizophrenia

Older Dads and Greater Risk For Autism, Schizophrenia
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Older men are more likely to have children with autism or schizophrenia due to random mutations that increase with age, says a just-published study in the journal Nature. Could these results help to explain the drastically higher rates at which autism is now diagnosed?

They may indeed, science writer Ewen Callaway says in an article accompanying the study, though other factors may also play a part.

In the US, the birthrate of fathers age 40 and over has increased more than 30 percent since 1980. The autism diagnosis rate has increased tenfold. Earlier this year, the Centers For Disease and Control reported that the prevalence rate for autism among American children is now 1 in 88, a 78 percent increase since 2007. Scientists and public health officials have also pointed to changes in the diagnostic criteria for autism spectrum disorders in the Diagnostic and Statistical Manual of Mental Disorders as a factor. With a better understanding of what autism is, doctors and parents have been better able to detect signs of autism in children.

Genetic Mutations and Brain Development

The new study is being hailed as it provides “some of the first solid scientific evidence for a true increase in the condition,” as Dr. Fred Volkmar, director of the Child Study Center at the Yale School of Medicine, says in the New York Times, in contrast to claims (often widely promulgated via the internet) that, for instance, vaccines have caused such a great increase in autism diagnoses that there is now an “autism epidemic.”

Scientists from the the Icelandic firm deCODE Genetics led the new study, in which whole-genome sequences of 78 trios of a mother, father and child, all from Iceland, were analyzed. Families without a history of mental disorders were the focus.

While women are born with a supply of egg cells for their whole lives, sperm cells divide every fifteen days or so and “continual copying inevitably leads to errors, in DNA as in life,” as the New York Times puts it. Fathers therefore pass on more mutations than mothers.

Scientists isolated de novo or spontaneous mutations that were present in a child but not in their father’s or mother’s DNA. The mutations must have occurred spontaneously in the egg, sperm or embryo. As Callaway explains,

Fathers passed on nearly four times as many new mutations as mothers: on average, 55 versus 14. The father’s age also accounted for nearly all of the variation in the number of new mutations in a child’s genome, with the number of new mutations being passed on rising exponentially with paternal age. A 36-year-old will pass on twice as many mutations to his child as a man of 20, and a 70-year-old eight times as many, Stefánsson’s team estimates.

The researchers estimate that an Icelandic child born in 2011 will harbour 70 new mutations, compared with 60 for a child born in 1980; the average age of fatherhood rose from 28 to 33 over that time.

While most of these mutations are harmless, Stefánsson’s team found that some are those associated with autism and schizophrenia.

As Stefánsson notes in the New York Times, it is indeed likely that de novo mutations might play a part in brain development because “at least 50 percent of active genes play a role in neural development, so that random glitches are more likely to affect the brain than other organs, which have less exposure.”

Older Men Pass On More Mutations

Earlier studies have also suggested that children born to older men are at a higher risk of being diagnosed with autism.

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7:38AM PDT on Oct 11, 2012

not rocket science people

5:06PM PDT on Aug 25, 2012

I think it is older mens sperm and immunizations

1:46PM PDT on Aug 25, 2012

With the new DSM-5 coming up soon we'll have to see how high is (or was) the reliability and validity of the diagnosis made with these children... At one point in time the complete withdrawal of social contact in the absence of obvious signs of organic problems was supposed to be the halmark but this changed over time making diagnosis or the criteria quite confusing. I hope for the best in terms of well conducted research and also hope the usual big money interests are held in check because this is a heartbreaking situation for parents and all involved. I for one, don't know if the coming new version of DSM will make things better or worse.)

5:03AM PDT on Aug 24, 2012

I know these articles can cover every aspect but it totally ignored the issue of the amount of toxins we carry in our bodies. Toxins, carcinogens and mutagens. And we accumulate more as we age. It may be normal for older men to have more genetic mutations in their sperm but you have to believe that the rising levels of toxins we have as years go on must have an affect on the developement and production of sperm. And this doesn't take into affect the reproductive affects of GMOs.
Humanity is like a marathoner eating cupcakes in training. We're poisoning our bodies and expecting somehow for humanity to perform well. It's just perverse.

12:55AM PDT on Aug 24, 2012

and all those of us who don't fit into that? My mother was 19 when she got pregnant, my father 26.

9:41PM PDT on Aug 23, 2012

well, the old guys won't be around to worry about who will take care of their kids when they are gone, let the wife worry about that.

8:18PM PDT on Aug 23, 2012


5:54PM PDT on Aug 23, 2012

As well as Downs. Europe has always known this.

1:38PM PDT on Aug 23, 2012

My neice has 5 children, she's only 35, and 2 of them are autistic. And the most children I've seen that are autistic are young parents. This research was paid by someone out there doing something shifty. I can't believe this one.

8:44AM PDT on Aug 23, 2012

No kidding. They need to study this? I always loved how men thought they had no biological clock! Maybe this will stop the old goats from looking for a young girl!

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