Men have a biological clock too

Older fathers produce children with a much higher risk of developing schizophrenia. Researchers point to 'strong evidence' that men, like women, have a 'biological clock' when it comes to having children, challenging commonly held beliefs that while older women risk having babies with birth defects, men can safely father children whatever their age.

The risk to a child of developing schizophrenia is thought to rise steadily as the age of the father increases, say researchers at Columbia and New York Universities and the Israeli Ministry of Health. They reviewed records of nearly 90,000 people born in Jerusalem between 1964 and 1976 and found that men between the ages of 45 and 49 were twice as likely as those under 25 to have children who develop schizophrenia. After the age of 50, the risk was increased threefold.

It is thought that the cause of the problem are sperm cells- passed on to children - which can accumulate mutations as men get older. The researchers believe that this may be the 'tip of the iceberg' in terms of conditions that may be linked to paternal age. Dr Susan Harlap of New York University said 'it would seem that the father's sperm is going to turn out to be just as important as the mother's egg'.

Dr Dolores Malaspina of Columbia University, who led the research, said that the findings add to a growing body of evidence that children fathered by older men may face some physical health problems. 'But', she added, 'this is the first psychiatric disease that's been linked to advancing paternal age'.