This article is more than 11 years old

This article is more than 11 years old

Children born to older men perform worse in intelligence tests than those with younger fathers, researchers have found.

A review of medical records of more than 30,000 children showed that those born to 20-year-old men scored on average three points higher in IQ tests than children whose fathers were 50-years-old when they were born.

The finding is the first to link men's age to impaired cognitive ability in their children and builds on recent work that suggests older men are more likely to have children with congenital heart defects, autism, schizophrenia and childhood cancers.

The same study found that children's IQ was marginally higher if they were born to older mothers, a finding scientists have put down to those women spending more time caring for and nurturing their infants.

The poorer performance of children with older fathers may be due to several factors, including how they interact with their children, but many scientists believe that genetic mutations that build up in the sperm of older men are to blame.

John McGrath at the Queensland Centre for Mental Health Research in Australia analysed records for 33,437 children born in the US between 1959 and 1965. The data included the children's scores on a variety of intelligence tests at the age of eight months, four years and seven years.

After taking into account differences in the parents' education and financial security, McGrath found a range of subtle impairments among children whose fathers were older, according to a report in the journal Plos medicine.

The differences in IQ scores are of concern because the age of fathers is rising. 25% of 1993 births in England and Wales were to men aged 35 to 54-years-old, but by 2003, that figure had risen to 40%.