HONG KONG, March 9 (Reuters) - Children of older fathers appear to perform less well in intelligence tests during infancy and childhood, a study by researchers in Australia shows.
In contrast, the study found that children with older mothers tended to gain higher scores in the same tests designed to measure the ability to think and reason, including concentration, learning, memory, speaking and reading skills.
Men and women are having children later particularly in developed countries. But while the effects of having children later for women are widely discussed, consequences of increased paternal age are not as well known.
Recent studies have drawn links between older fathers and specific health problems in their children, including birth deformities and cancer, as well as neuropsychiatric conditions such as autism and schizophrenia.
In the study, the researchers analysed data from intelligence tests taken by 33,437 children who were born between 1959 and 1965 in the United States.
The children were tested at 8 months, 4 years and 7 years and were assessed for their sensory discrimination, hand-eye coordination, reading, spelling and arithmetic ability.
They found that the older the father, the more likely the child would have lower scores on the various tests.
In contrast, the older the mother, the higher the scores of the child in the cognitive tests.
"Previous researchers have suggested that the children of older mothers may perform better because they experience a more nurturing home environment; if this is the case, this study suggests that children of older fathers do not necessarily experience the same benefit," the researchers wrote in a statement.
The researchers said the lower scores obtained by offspring of older men may have to do with mutation.
"Unlike a woman's eggs which are formed when she herself is in the womb, a man's sperm accumulates over his lifetime, which previous studies have suggested can mean increased incidence of mutations in the sperm at an older age," they wrote.
The study was published in the open-access journal PLoS Medicine and can be found here doi=10.1371/journal.pmed.1000040. (Reporting by Tan Ee Lyn)