Older men may have less intelligent kids

Older men may have less intelligent kids
10:08 09 March 2009 by Emma Young
While men, unlike women, can continue having children into old age, there could be a price to pay in terms of their child's intelligence.
John McGrath at the University of Queensland, Australia, and colleagues analysed data on more than 33,000 US children at the age of eight months, four years and seven years.
They found that those born to older dads scored more poorly on a range of intelligence tests that looked at concentration, memory, reasoning and reading skills. In contrast, the kids of older mothers scored more highly than those of younger mothers.
IQ drop
"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."
However, the differences in scores for the children of older and younger dads were small, amounting to about two IQ points for the child of a 20-year-old father compared with the child of a 50-year-old man.
The team suspects that age-related accumulations of genetic errors in the cells that produce sperm might account for their results. This might explain other work finding increased risks of schizophrenia, autism and bipolar disorder in the children of older dads, adds McGrath.
"I don't think we have enough evidence to say that fathers should avoid parenthood after a certain age," he says, "but I think we do need to educate people that there are risks they didn't know about."
Journal reference: PLoS Medicine ()DOI: 10.1371/journal.pmed.1000040)