Older Dads and Greater Risk For Autism, Schizophrenia

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. Other studies have linked increasing maternal age to children born with developmental disorders; older women are at more risk of having a child with chromosomal abnormalities like Down’s Syndrome (and, in a previous generation, women were outright blamed for “causing” a child to become autistic by being emotionally frigid “refrigerator mothers” who failed to bond with their children).

The new study, though, has found that, in cases of developmental and psychiatric problems, most of the genetic risk comes from the sperm, not the egg.

So, Should Older Men Not Have Kids?

In an editorial accompanying the study, Alexey Kondrashov of the University of Michigan’s Department of Ecology and Evolutionary Biology and the Life Sciences Institute, writes that, in some cases, “collecting the sperm of young adult men and cold-storing it for later use could be a wise individual decision.”

Despite this, scientists underscore that the study is not meant to give older men reason to forego having children, as most genetic mutations have no consequences. Mark Daly, a geneticist at Massachusetts General Hospital in Boston, also notes that autism is highly heritable and that “most cases are not caused by a single new mutation — so there must be predisposing factors that are inherited from parents but are distinct from the new mutations occurring in sperm.”

As for my own teenage autistic son, Charlie: While there are no autism spectrum disorder diagnoses in our families, there is a history of mental disorders in both my husband’s and my families. (Indeed, a couple of my relatives seem likely candidates for a diagnosis of Asperger’s Syndrome.) With more individuals diagnosed with ASDs, my main hope that is that greater understanding and awareness can make more programs, accommodations and services available (with adequate funding), so those on the spectrum can lead good lives in communities that support them.

 

Related Care2 Coverage

Denial of Heart Transplant For Autistic Man Sparks Outrage

3 Books On Raising Children With Disabilities (Slideshow)

Website Forced to Remove Misleading Vaccine-Autism Claims

 

 

Photo by Sellers Patton

24 comments

Kathy Perez
Kathy Johnson3 years ago

not rocket science people

Luna Starr
luna starr3 years ago

I think it is older mens sperm and immunizations

Liliana G.
Liliana Garcia3 years ago

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.)

Joseph Belisle
Joseph Belisle3 years ago

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.

Jessica Larsen
Janne O.3 years ago

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

Gloria H.
Gloria H.3 years ago

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.

Terry V.
Terry V.3 years ago

And.......................what????????????????????

A N M.
anne M.3 years ago

As well as Downs. Europe has always known this.

Lynda Duke
Lynda Duke3 years ago

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.

Felicia S.
Phyllis S.3 years ago

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!