Older Fathers' Sperm May Produce Children With Slightly Lower IQs

By Eliza Strickland | March 10, 2009 2:56 pm

baby hand fatherMen who are older when they father children tend to have children who score slightly lower on IQ tests and other measures of cognitive function, according to a new study. That conclusion, which researchers called unexpected and startling, adds to a recent surge of evidence that, like women, men also have a biological clock. Older fathers have been linked to a range of health problems, including an increased risk of birth deformities, autism and neuropsychiatric conditions, such as schizophrenia and bipolar disorder…. Experts believe mutations in a man’s sperm, which build over time, may be a factor [BBC News]. 

However, lead researcher John McGrath says that the findings shouldn’t cause panic. “With respect to childhood intelligence, a vast array of factors is far more powerful than paternal age,” McGrath cautions. These factors include nutrition, health care and family income [Science News]. Researchers say that adjusting for socioeconomic factors like family income lessened the link between paternal age and children’s cognitive scores, but didn’t erase it. The average IQ of a child born to a 20-year-old father was six points higher than that of a child with a 50-year-old father, but adjustments reduced the difference to three points. Researchers say that gap is statistically significant, but is modest in practical terms [Science News].

In the study, published in the journal PLoS Medicine, researchers conducted a broad new study of data collected in the 1950s and 60s. The researchers analyzed the scores of 33,437 children who … had been tested at regular intervals in a variety of cognitive skills, including thinking and reasoning, concentration, memory, understanding, speaking and reading [The New York Times]. Researchers saw the link between paternal age and test scores until the children reached the age of seven, when the study stopped.

But in a rather befuddling contrast, the kids of older mothers scored more highly than those of younger mothers. “Folk wisdom tells us that the offspring of older parents should get better opportunities and better nurturing,” says McGrath, and these social factors would be expected to help boost their child’s mental performance. “That is exactly what we find for mothers – but exactly what we don’t find for dads, which is startling” [New Scientist].

Dolores Malaspina, who has studied the link between older fathers and the risk of schizophrenia, says the new study helps refute the outdated notion that a father’s age has no impact on a child’s health. “I think there has been a bit of a cultural bias against even looking at this issue, but finally people are willing to entertain this…. It turns out the optimal age for being a mother is the same as the optimal age for being a father,” Dr. Malaspina said. “The fact that men can stay fertile longer is a different issue” [The New York Times].

Related Content:
80beats: Older Men Are More Likely to Father Bipolar Children
80beats: Men Have a Biological Clock, Too looks at male fertility rates
DISCOVER: The Male Biological Clock examines the link between older fathers and autism rates
DISCOVER: The Biology of … Schizophrenia finds that older fathers can play a role in this disease, too

Image: iStockphoto

CATEGORIZED UNDER: Health & Medicine, Mind & Brain
  • john o roberts

    Perhaps overlooked is the fact that older men who father children have signifigantly lower IQ’s than those who don’t.

  • Charlotte

    Historically older males are wealthier by inheritance and beat younger males to the fitter wife stock. Today modern older males tend to be over-indulged or bogged down by career demands and over-stretched, immune-compromised males make weaker sperms and less focused fathers. If we care to pay attention – male biological clock are ticking louder than the female one. All along. Not a mega revelation at all, but some obvious common sense “facts” long been denied by the formerly male-dominated world of medical science.

    Biology have already shown us males reach their vitality peak earlier than females, regardless of nutritional advancement. It makes simple common sense that young fit 20-30 yr old males have more vital sperms. Smarter females also tend to develop fitter body and better overall MENTAL health. They also tend to breed later in their 30′s and make overall more capable and involved mothers. Pretty obvious. The older wealthier males tend to breed with the more desperate, immature, lower-IQ, insecure, dependent females, which have compromised the quality of the human genetic pool for the last few thousand years.

    Smarter females mostly CHOOSE to have a child out of MOTHERING needs. Dumber females mostly CHOOSE to have children out of husband-capturing SECURITY needs. Which group makes more loving mothers?

    We have for too long overvalued longer fertility span, overvaluing quantity instead of QUALITY of off-springs.

    If I had a choice, give me a stable 33 yr old mother – fit 25 yr old father anytime, over the gloomy prospect of a rich old schizoid father with a dumb brat mother. A 5-10 year difference between older moms and younger dads are also socially healthier – there would be less lonely old people in the world.

    The human stock and social imbalance may improve gradually as women become wealthier earlier, and the smarter young males stop buying to their father’s superman fantasy and accept male biological ain’t the same after 25, and choose to give their off-springs younger fitter fathers.

  • http://none Ann Pima

    We have a family member who is 84 this winter and he has just had a 7 lb 11 oz baby girl with a 23 year old woman. We have our doubts about the paternity of this child, among other things. How does the family begin to cope with this situation correctly. They claim to be in love. The baby is beautiful but only 4 mos old so can’t tell much about intelligence right now. Is this really plausible that this is his child.

  • ilus77

    Charlotte,

    jealous much?…….

  • http://www.learnelectricguitaronline.net jamplay review

    Does the sperm “age” along with the older male? Interesting article. I think you always have a good mix of high, middle and low IQ people regardless of the age. But it would stink to be 80 years old and have a 5 year old! Lord, I already went through it once, don’t want to do it again!

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