Research from The University of Queensland has revealed the older a dad is the more likely his children will have reduced cognitive abilities.
Professor John McGrath, from UQ's Queensland Brain Institute, said the study could have implications for a society that is having children later in life.
He said while recent research had shown a link between the age of a father and an increased chance of schizophrenia and autism in the children, there has been less focus on the age of father and cognition.
"The results were quite startling as it was thought that the age of the father was less of a concern compared to the age of the mother," Professor McGrath said.
"Now we are getting more evidence of the age of the father being just as important. The older a dad is, the worse his children tend to do in intelligence tests."
The research, published in medical journal PLoS Medicine today, re-analysed data from one of the largest studies of children in the United States, the Collaborative Perinatal Project.
More than 33,000 children were tested at eight months, four years and seven years on a variety of intelligence tests and when Professor McGrath and his colleagues looked at the results against the age of the fathers a pattern soon became clear.
"Frankly, we were surprised to come up with such a clear-cut finding," Professor McGrath said.
"We are concerned that older men accumulate more mutations in the developing sperm cells. These mistakes then pile up and increase the risks of problems in the children and it is possible that these mistakes will carry on into the next generation."
Professor McGrath said the difference in intelligence was the exact opposite for children of older women, which made the findings even more startling.
"Offspring of older women do better in similar tests, but this is usually put down to the socio-economic status of women. With the older dads, we wonder if the association is related to mutations in the developing sperm," he said.
Professor McGrath and colleagues at QBI and the Queensland Institute of Medical Research are currently using mouse models in order to find the underlying genetic factors that may explain the association between advance paternal age and child development.