Men 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who has studied the link between older fathers and the risk of schizophrenia, says the new study helps refute the outdated notion that a father’s age has no impact on a child’s health.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].
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