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Older Fathers, Lower IQ in Kids?

Study Shows Children of Older Dads Had Lower Performance on Intelligence Tests

Intelligence Tests for Children of Older Fathers continued...

While the study findings may suggest the best combination of parents is an older woman with a younger man, McGrath says it's too early to make any specific recommendations.

"For the moment, our study suggests that paternal age, like maternal age, also should be 'on the radar screen'" for researchers, he says. As research accumulates, he says, "we can put this knowledge into the public health equation," weighing it along with many other factors before dispensing advice.

What's behind the link between older fathers and lower IQ? "There is a growing body of evidence suggesting that the sperm of older dads develop more mutations, that is, spelling mistakes in the DNA code," McGrath says. His team is researching this idea further in animal studies comparing young mice with older ones.

Still, it's important to put the paternal age in perspective, McGrath says. "The significance of the effect linking paternal age and child cognition is small compared to many other socio-cultural factors -- for example good prenatal nutrition, good nutrition for the offspring, good education, nurturing home life, excellent teaching and school opportunities [and so on]."

Second Opinions

"We have known about the paternal age effect for many years," says Harry Fisch, MD, director of the Male Reproductive Center and director of urologic microsurgery at Columbia University Medical Center of New York Presbyterian Hospital. Yet, he says, "We are just starting to scratch the surface."

Testosterone levels begin to decline slowly at age 30, Fisch says. Ideally, men should father children "sooner rather than later," he says.

"The 20s and early 30s are ideal, but real life intervenes," he says, making that time frame not feasible due to lack of a partner, difficulty getting pregnant, financial restraints, or a host of other factors.

In a perspective on the study, published in the same issue of PLoS Medicine, Mary Cannon, MD, of the Royal College of Surgeons in Dublin, Ireland, says it is important to take socioeconomic factors into account when looking at the effect of a father's age (as well as a mother's).

She points out that taking into account the socioeconomic factors is not a precise science, and that if researchers could truly adjust for every relevant socioeconomic variable, the effect of the father's age on the child's intelligence might be wiped out completely. She, too, calls for more research.

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