Children’s intelligence may be affected by a father’s advanced age, according to a new study published this week in the journal PLoS Medicine.
The report is the latest to suggest that a man’s age matters when it comes to having children – a phenomenon that’s come to be called the “male biological clock.”
The study looked at about 33,000 youngsters fathered by men 14 to 66 years old between 1959 and 1965 in the United States. The children were followed over time, and when they were evaluated at ages 4 and 7 those born to older fathers performed somewhat worse on standardized intelligence tests.
“The offspring of dads who are about aged 50 are scoring about two IQ points less than offspring of fathers who are about 20,” Professor John McGrath of the Queensland Brain Institute in Australia told ABC News.
“It’s a very small effect, but when we control for things like the mother and father’s education, and the mother and father’s socio-economic status, this link between paternal age and how the children are going is still there,” he continued.
But is it a real effect? Perhaps not, according to Professor David Hay of Curtin University of Technology, also in Australia, and also quoted by ABC.
“The average person differs by about four IQ points between successive testing; it’s really not a very big effect,” he said.
Interestingly, McGrath’s study confirms that children born to older women perform better on intelligence tests -- a result that confirms similiar findings from other studies.
Unlike men, who produce sperm throughout their lives, women are born with all the eggs they’ll ever have. As a result, some of the age-related problems men face – such as the potential for DNA copying errors in sperm that are constantly replicating -- aren’t shared by women.
(Of course, as women age the quality of their eggs diminishes and the potential for poor pregnancy outcomes increases, along with the risk of Down syndrome.)
DNA copying errors or other age-related damage to sperm might be a reason why older dads have children with more medical problems such as schizophrenia, autism-related disorders, bipolar disorders and certain types of dwarfism, researchers speculate.
That hypothesis isn’t proved. The studies to date have noted an associated between paternal age and kids with these medical conditions but haven’t established causality. Most kids born to older dads are perfectly normal and don’t have these medical problems.
In an editorial accompanying the new article, Dr. Mary Cannon, a psychiatrist at the Royal College of Surgeons in Dublin called for more research into the topic and said “the body of evidence implicating paternal age as a risk factor for a range of adverse offspring outcomes should not be ignored,” Bloomberg reported.
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