Old dads schizophrenia autism cancers MS type 1 diabetes

Not the sharpest? Blame old dad
Font Size: Decrease Increase
Print Page: Print
Leigh Dayton, Science writer March 10, 2009
Article from: The Australian
IF your IQ isn't up to brain surgery or a Nobel Prize, blame your ageing dad.
Intellectual whizzes, on the other hand, can thank their older mums.
The surprising conclusions come from an Australian and US team led by neuroscientist John McGrath of the University of Queensland's Brisbane-based Queensland Brain Institute.
In their study of 17,148 boys born in the US between 1959 and 1965, they found that children conceived by older fathers performed less well on a range of thinking tests given at eight months, four years and seven years than those born to younger dads.
They took into account other possible factors such as education, mental health and income, with the same result.
"While we didn't find a clean threshold above or below which there is a risk (of lower IQ), the risk increased steadily the older the dads were," Professor McGrath said yesterday.
Writing in the US journal Public Library of Science Medicine, his team said their results contrasted sharply with earlier studies showing that the older the mother at conception, the smarter the child.
According to Professor McGrath and his colleagues, the difference may lie in the male and female reproductive systems. A woman is born with a fixed number of eggs that have undergone 22 cell divisions in the womb. But sperm cells divide every 16 days after a boy reaches puberty. By age 20, the original sperm cells have divided roughly 150 times; by age 50, 840 times. The more cell divisions, the more mutations; the more mutations, the greater the chance a child will be born with physical or neurological abnormalities.
Until recently, studies of the risks of later conception focused on women. It's well known, for instance, that as women age, the likelihood increases of their having a child with the developmental and intellectual disorder Down syndrome.
In a review of the team's paper, also in PLOS Medicine, psychiatrist Mary Cannon of the Royal College of Surgeons in Ireland wrote that evidence was accumulating that advanced paternal age was a risk factor for neuropsychiatric conditions such as schizophrenia and autism, as well as physical problems such as cleft lip and palate, childhood cancers and congenital heart defects.
"The body of evidence implicating paternal age as a risk factor for a range of adverse offspring outcomes should not be ignored," she concluded.
To tease out precisely why older dads sire youngsters with IQ scores up to three points lower than younger fathers, Professor McGrath's group has begun investigating a group of 7000 babies born in Brisbane in the 1980s.
They are also studying the phenomenon in mice to identify the mechanism or mechanisms involved.
"Age is something to factor in when planning a family," Professor McGrath said.

Older Paternal Age and Schizophrenia James Watson co-discoverer of DNA structure is concerned because he was 42 when his son was born

His son suffers from schizophrenia.
From The Sunday Times
March 8, 2009
Not too bright? Now the blame is on your old man
Jonathan Leake, Science Editor

CHILDREN with older fathers seem to perform worse in intelligence tests, according to a study due out this week.
They tended to obtain significantly lower scores in a variety of cognitive tests than those born to younger fathers, researchers have found.
The results could be controversial. Until recent years it had been thought that it was a mother’s age that had most impact on the health and abilities of children. The father’s age, by contrast, was thought to be much less important.
The research, led by John McGrath, of the Queensland Brain Institute at the University of Queensland in Australia, suggests such ideas need rethinking.
“The offspring of older fathers show subtle impairments on tests of neurocognitive ability during infancy and childhood,” he said. “In light of the trends to delay fatherhood, the clinical implications and the mechanisms underlying these findings warrant closer scrutiny.”
Other research has shown linkage between advanced paternal age (men over 35) and an increased risk of neurodevelopmental disorders, such as autism and schizophrenia, as well as dyslexia. Such findings prompted James Watson, co-discoverer of the structure of DNA, to speak of his concern. His son Rufus suffers from schizophrenia and as more is uncovered about its causes Watson has publicly questioned if he is to blame. “I worry that I was 42 with Rufus,” he says. “I read that the frequency of schizophrenia goes up with the age of both parents.”
The tests, designed to measure the ability to think and reason, also generated a second startling finding — that children with older mothers gain higher intelligence scores.
McGrath analysed data on 33,437 Americans born between 1959 and 1965. All were tested at eight months, four years and seven. The data set, despite its age, remains one of the best resources. McGrath also used advanced statistical techniques to remove environmental influences.
For McGrath one of the key questions is the underlying biological mechanisms. One idea is that as men age the cells that produce sperm suffer increasing numbers of mutations, which are passed on to an offspring.
Why, though, would children born to older mothers tend to have higher intelligence? McGrath suggests this is because women’s eggs are formed when they are still in the womb and so their DNA is protected from mutation until they are used.