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The Essential Fine Points of New Study on Paternal Age as Risk Factor for Schizophrenia, Autism

You probably read this headline about new research tying older dads to increased risks for schizophrenia and autism from yesterday’s NYT and other news outlets. The new study from Iceland actually has the most to report about autism — finding that paternal age could account for 20 to 30 % of autism cases while raising the risk for SZ in a child for men over 40 to just around 2% overall — but here’s the gist from Benedict Carey’s excellent NYT’s story:

Older men are more likely than young ones to father a child who develops autism or schizophrenia, because of random mutations that become more numerous with advancing paternal age, scientists reported on Wednesday, in the first study to quantify the effect as it builds each year. The age of mothers had no bearing on the risk for these disorders, the study found.

The nuance you may have missed is that this finding is not in itself new. As I write about in my book, A Lethal Inheritance, other studies have made this linkage — especially between paternal age and SZ – over the past decade. What’s new here is the quantifying of specific paternal ages and levels of risk. It is my firm belief that the more specifics you know about your health or mental health risks, the better…so this is more valuable data for current and future parents. Here again is Carey:

The new report quantifies that risk for the first time, calculating how much it accumulates each year.

The research team found 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, the study found.

Let’s Talk About Risk

When dealing with a parental risk factor like age — something you can usually do nothing to change (except the obvious though not always available option of planning to father children at a younger age) — it’s important to weigh other health and environmental risks to get to your individual “absolute risk.”

On this score I highly recommend a PLOS article (I now work at PLOS as a blog editor) explaining how one should understand “relative” vs. “absolute risk”.

If you know your risk is slightly or even more than a little higher for fathering or mothering a child with a psychiatric disorder based on genetics or any other reason, there are still many things you as parents can do to give your child the best chance to develop a healthy brain.

The other important thing about this new paternal age study is that it looked at children without a known family history of autism or schizophrenia. (The causes of these genetic mutations that are more common in older fathers, with sperm that have been exposed to more environmental risks, are currently unknown. Once again, from the NYT’s account of the new research:

The new investigation, led by the Icelandic firm Decode Genetics, analyzed genetic material taken from blood samples of 78 parent-child trios, focusing on families in which parents with no signs of a mental disorder gave birth to a child who developed autism or schizophrenia. This approach allows scientists to isolate brand-new mutations in the genes of the child that were not present in the parents. Most people have many of these so-called de novo mutations, which occur spontaneously at or near conception, and most of them are harmless.

Read the whole story here.

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