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Older Dads and Their Kids' IQs

Everyone has heard about women's biological clock. But do men have one, too?

Well, men don't go through menopause like women do, and most remain fertile throughout their lives. But there is a growing body of evidence that children born to older fathers may be at increased risk for certain health problems. Now, a new study suggests they may also be at risk for lower IQs.

John McGrath of the University of Queensland in Australia and his colleagues analyzed data that had been collected on 33,437 children born in the United States between 1959 and 1965. Each child was tested at 8 months, four years and seven years of age with a variety of tests to measure intelligence and other cognitive abilities, such as hand-eye coordination and reading, spelling and math skills.

After adjusting for other factors that can affect how well kids score on such tests, such as their socioeconomic status, the researchers analyzed the data to see if the age of the father affected the results. The researchers found that the older the father the lower the child scored on all the tests except for one that measured physical coordination.

In contrast, the older the mother the better the children tended to score, the researchers reported this week in the journal PLoS Medicine. That is consistent with previous studies, which found that while older mothers are more likely to have problem pregnancies their children do tend to score higher on such tests. Researchers have speculated that may be because older mothers tend to have higher incomes and education, enabling them to offer a more nurturing environment at home. The new study suggests that doesn't hold for older fathers.

It remains unclear why these older fathers would have children more prone to these problems. But the researchers note that a man's sperm may be more prone to genetic defects as he ages. Previous studies have found evidence suggesting that children born to older fathers may also be at increased risk for a variety of disorders, including schizophrenia, autism, bipolar disorder and dyslexia.

But the researchers say more studies are needed to confirm the findings and explore what the causes might be.

By Rob Stein  |  March 12, 2009; 7:00 AM ET
Categories:  Motherhood  
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what are the definitions the scientists used for "older father" and "older mother" in these studies?

Posted by: needtoknowmore | March 12, 2009 10:38 AM | Report abuse

An extremely important independent variable has not been isolated in the study. One would assume that the older the father, the less likely that the child is the first born. In general, parental expectations of the first born are higher, while expectations of later children are not as high.

To be valid, the study would need to isolate first born children and contrast the I.Q. of first born children of young fathers with the I.Q. of first born children of older fathers.

This is poor science. The majority of children of older fathers are not first born, and expectations of them are not as high. Not isolating this significant independent variable makes the study invalid.

Posted by: tharriso | March 12, 2009 11:16 AM | Report abuse


What is the purpose of this article? Seriously. As comment 1 asks, what are the ages? How about a link to the actual study? This article, from my perspective, offers an example of extremely poor journalism if it's journalism at all. Seems more like a cheat sheet to exact some readership stats.

Thumbs big time down on this article.

Posted by: cherrib | March 12, 2009 12:23 PM | Report abuse

First, apology. The link is in the article and I missed that. I apologize for this error.

However, the remaining comment stands as is because more is necessary than just a summary of the abstract, a lot more. Whoever wrote this article missed some important questions.

Posted by: cherrib | March 12, 2009 12:33 PM | Report abuse

Oh please - this is a whole lot of crap. I agree with needtoknowmore, what was considered an "older" father??? My father was 42 when I was born (the youngest of 6) and my IQ is over 140. With a PhD from Johns Hopkins; I would need only a few minutes to blow their data to smithereens. Ridiculous.

Posted by: BullyLover | March 12, 2009 12:36 PM | Report abuse

BullyLover - the plural of anecdote is not data. The study did not say that ALL children of older dads have low IQs. It says that they TEND to have lower IQs. So that means that just because you are, evidently, amazingly intelligent, it doesn't mean that the study is flawed. Now it may be flawed in other ways as others have mentioned - but your comment means nothing.

Posted by: DCResident00 | March 12, 2009 12:41 PM | Report abuse

This article is too brief to explain the study completely - especially all of the variables for father's age, nominal placement of the child in relation to siblings (i.e. first, second, third, etc) and overall health. One link that would be interesting to explore would be whether the age of the father (and his DNA) is linked to genetic defects such as Down Syndrome. Usually the link to these disorders is the age of the mother. That "sticky" 21st chromosome may be the result of the father.

Posted by: Moderation | March 12, 2009 12:50 PM | Report abuse

Hey, BullyLover-

A Hopkins PhD should know better than to treat a sample size of one as statistically significant.

You're an idiot.

Posted by: thermowax | March 12, 2009 1:08 PM | Report abuse

It is worth looking closely at these data and remembering that statistical significance and practical significance are two different beasts. Although the differences reported between the IQs of younger and older fathers are statistically significant, the means for both groups fall solidly in the average range. In practice, it would be hard to tell the average individual in one group from the average individual in the other, and most individuals in both groups would be functioning just fine.

Posted by: researcher3 | March 12, 2009 4:57 PM | Report abuse

One word:


It's an enzyme that, during the numerous incidents of miosis -- the creation of new sex cells -- cuts off the ends (telemeres) of the chromosomes, and which may make the genes located towards the ends of the chromosomes dysfunctional. The older the male parent (female zygotes are created much earlier in the life cycle and are not so effected--although there may be other genetic effects), the more likely the chance of dysfunctional genes being transmitted to their children.

This is what happened with Dolly the Sheep: she was cloned from adult chromosomes; thus she was born an adult sheep, and quickly succumbed to adult diseases although she was but a few years old.

tk, PhD

Posted by: tkavanag | March 12, 2009 8:31 PM | Report abuse

Two quotes that say to me this is a weak and perhaps downright stupid article:

"After adjusting for other factors that can affect how well kids score on such tests, such as their socioeconomic status..."
No information here on how. How do you adjust for socioeconomic status? Add a few IQ points? Ask questions about pickup trucks and country music?

But the grand prize for bad journalism and/or bad research:
"The researchers note that a man's sperm may be more prone to genetic defects as he ages."
Is it more prone? Is there research on the genetic makeup of sperm of older men SOMEWHERE that supports this statement? As presented here it's on a level with talk at the barber shop.

Posted by: kls1 | March 13, 2009 1:09 AM | Report abuse

I've read that men's little gray cells deteriorate three times as fast as women's, so perhaps their sperm deteriorates at a similar rate.

Posted by: dotellen | March 13, 2009 1:55 AM | Report abuse

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