Shocker of a discovery for older dads
Sunday March 15, 2009
Shocker of a discovery for older dads
Insight Down Under
By JEFFREY FRANCIS
LIKE some famous movie stars and top musicians, many men in Australia and other Western nations are more inclined to marry late in life and become fathers when they are in their 40s, 50s and even 60s or 70s.
What they didn’t realise until now is that the children they fathered are at risk of being less intelligent and the performance of their brainpower leaves much to be desired in their early years.
This shocking discovery, the first ever, in a new study of researchers led by world-renowned Australian psychiatrist and brain expert Dr John McGrath, was published last week in a medical journal, PLoS Medicine.
But an interesting contrast is that children born of older women tend to score higher in the same tests designed to measure the ability to think and reason, including concentration, learning, memory, speaking and reading skills.
Whether this has anything to do with older mothers’ better socio-economic status, better health care and health literacy is not known, though Dr Grath’s research noted these conditions.
These factors do not appear to help children fathered by older men in the same way as children of older mothers, he says.
Instead, some kind of biology appears to be at work. As men age, the sperm they produce appears to acquire genetic mutations.
And while the men’s fertility declines with age, the number of damaged sperm which are still able to fertilise a woman’s egg increases.
“It was very clear: If your mother was older, you were doing better. But it went the other way for the dad,” declares Dr McGrath, who is director of Epidemiology and Developmental Neurobiology at Queensland University in Brisbane.
The bespectacled young-looking professor has carried out various research, one of which led to him and his group discovering the importance of pre-natal vitamin D on brain development.
A winner of several national and international awards, Dr McGrath has published 110 peer-reviewed papers, three books and 13 book chapters.
Hitherto, previous studies have linked advanced paternal age to reduced fertility rate and associated problems such as increased risks of birth deformities and neuropsychiatric conditions. For example, becoming fathers at 40 or older has been linked repeatedly in the past to their offspring being at a significantly higher risk of schizophrenia, autism and a rare syndrome that causes facial or skull abnormalities.
Now, it has been discovered for the first time that children fathered by older men have an average score on the Stanford Binet Intelligence Scale of six points lower than those fathered by men who were just 20.
Yet all the children have better access to health and educational services.
Although some scientists believe that the 20s and 30s are the ideal years for fatherhood, Dr McGrath stresses that researchers could not yet predict the ideal maternal and paternal age that might result in a healthy, intelligent child.
“Future generations will still be bearing the age-related mutations their fathers, grandfathers or great-grandfathers accumulated,” he says.
Dr McGrath points out that there is no single age threshold at which the risk increases, as is the case with women and Down syndrome after 35, and a continual decline for men.
“We, as a society, need to worry about the age of fatherhood a little bit more than in the past,” he says.
“While everyone is aware of a decline in fertility as we age, maybe the general public needs to be aware that there may be something else happening. We need to work out what underlies this association.”
His group of researchers, who have studied data collected from more than 33,400 American children and parents ranging in age from 14 to 66, has found a correlation between advanced paternal age and lower intelligence scores.
The children were tested at eight months, four years and seven years of age. They were also assessed for their sensory discrimination, hand-eye coordination, reading, spelling and arithmetic ability.
However, some researchers have suggested that children of older mothers might do better because they experience a more nurturing and attentive home environment.
If this is correct, how is it that Dr McGrath’s study did not show the same benefit among children of older fathers?
But his group found that genetics and social factors might play a role in their findings. They say that a woman’s eggs are formed before birth, so DNA may stay relatively stable.
Sperm, on the other hand, is produced over a man’s lifetime and may gain mutations as men grow older, they say.
Despite the impact Dr McGrath’s findings have caused on society, he says humbly that it is “small and preliminary”.
Jeffrey Francis is editorial consultant, Australasia-Pacific Media