MELBOURNE : Children fathered by older men are likely to be less intelligent than the offspring of younger dads, Australian and US scientists have found in a report published Tuesday.
The research contrasted sharply with earlier studies showing that older mothers produced children more likely to record above average intelligence scores, the researchers concluded.
Lead scientist John McGrath, from the Brisbane-based Queensland Brain Institute, said the result was a world first and had implications for men in Western societies who have delayed fatherhood until their 40s or older.
"The offspring of older fathers show subtle impairments on tests of neurocognitive ability during infancy and childhood," he said in the new research.
"In light of secular trends related to delayed fatherhood, the clinical implications and the mechanisms underlying these findings warrant closer scrutiny."
Researchers examined data collected on 33,000 children in the United States between 1959 and 1965 fathered by men aged from 15 to 65.
They found that the children of older dads performed less well in intelligence tests conducted at age eight months, four years and seven years.
The researchers said previous studies had linked older fathers to an increased risk of health problems in their children, including schizophrenia, autism, dyslexia, epilepsy and dwarfism.
However, the study published in the US journal Public Library of Science Medicine is the first to suggest there may also be a link with general intelligence.
McGrath and his team said their research could not draw conclusions on how having an older father impacted on children later in life because the subjects in their study were only examined until they were aged seven.
One theory about the difference in results for older fathers and mothers lies in differences between the male and female reproductive systems.
Women's eggs undergo 22 cell divisions in the womb, while male sperm cells have divided 150 times by age 20 and 840 times by age 50.
This increased the chance of "copy error mutations" that could lead to health problems, researchers said.
The research contrasted sharply with earlier studies showing that older mothers produced children more likely to record above average intelligence scores, the researchers concluded.
Lead scientist John McGrath, from the Brisbane-based Queensland Brain Institute, said the result was a world first and had implications for men in Western societies who have delayed fatherhood until their 40s or older.
"The offspring of older fathers show subtle impairments on tests of neurocognitive ability during infancy and childhood," he said in the new research.
"In light of secular trends related to delayed fatherhood, the clinical implications and the mechanisms underlying these findings warrant closer scrutiny."
Researchers examined data collected on 33,000 children in the United States between 1959 and 1965 fathered by men aged from 15 to 65.
They found that the children of older dads performed less well in intelligence tests conducted at age eight months, four years and seven years.
The researchers said previous studies had linked older fathers to an increased risk of health problems in their children, including schizophrenia, autism, dyslexia, epilepsy and dwarfism.
However, the study published in the US journal Public Library of Science Medicine is the first to suggest there may also be a link with general intelligence.
McGrath and his team said their research could not draw conclusions on how having an older father impacted on children later in life because the subjects in their study were only examined until they were aged seven.
One theory about the difference in results for older fathers and mothers lies in differences between the male and female reproductive systems.
Women's eggs undergo 22 cell divisions in the womb, while male sperm cells have divided 150 times by age 20 and 840 times by age 50.
This increased the chance of "copy error mutations" that could lead to health problems, researchers said.
