Older dads risk slower children

Men should not leave fatherhood too late because children of older fathers are more likely to suffer from a range of psychological and educational problems, scientists have warned.

The biggest study of its kind has found that the children of fathers over 45 were at greater risk of autism, bipolar disorder and schizophrenia, and of having a lower IQ and a poorer academic record.

Women have traditionally been warned that they should not delay motherhood, but, because there is no male menopause, men have tended to believe that they can father children at any age.

However, when researchers at Indiana University, in the US, and the Karolinska Institute, in Sweden, looked at the development of more than 2million children born between 1973 and 2001 they discovered worrying trends.

Children born to a 45-year-old man were 13 times more likely to have attention deficit hyperactivity disorder than those born to a 24-year-old man, 3.5 times more likely to have autism and 25 times more likely to have bipolar disorder.

They were also nearly twice as likely to have dropped out of school early and have a lower IQ.

"We were shocked by the findings," said Brian d'Onofrio, the report's lead author.

"The specific associations with paternal age were much, much larger than in previous studies. In fact, we found that advancing paternal age was associated with greater risk for several problems such as attention deficit hyperactivity disorder, suicide attempts and substance abuse."

Over the past 40 years the average age of childbearing has been increasing steadily for both men and women.

As men age, they are exposed to the cumulative effects of environmental toxins that have been shown to cause DNA mutations in sperm.