Older fathers put offspring at risk

WASHINGTON - Children fathered by older men may run a much higher risk of developing schizophrenia - evidence that men, like women, have a "biological clock" when it comes to having children.

The new research findings blow a gaping hole in the commonly held belief that while older women run a higher risk of having babies with birth defects, men face no such risk when fathering children, even at an advanced age.

A child's risk of developing the devastating mental illness rises dramatically and steadily as the age of the father increases, say the researchers, at Columbia University College of Physicians and Surgeons, New York University School of Medicine and Israel's Ministry of Health.

They reviewed the records of 87,907 people born in Jerusalem from 1964 and 1976. They found that men between the ages of 45 and 49 were twice as likely as those under 25 to have children who develop schizophrenia. Men 50 or older ran three times the risk of the fathers under 25.

The study said 26.6 per cent of the schizophrenia cases could be attributed to the father's age, while the age of the mother appeared to play no role. Paternal age was responsible for two-thirds of the cases when the father was over 50.

Columbia University's Dr Dolores Malaspina, who led the study, said the findings augmented a growing body of evidence of an increased likelihood of health problems for children of older men.

"This is the first psychiatric disease that's been linked to advancing paternal age."

Schizophrenia is a group of psychotic disorders marked by delusionary thinking, hallucinations and bizarre physical behaviour. It is thought to stem from a poorly understood combination of genetic and environmental factors. It afflicts 1 per cent of people worldwide.

The study, appearing in the journal Archives of General Psychiatry, backs the notion that as men age, sperm cells can accumulate mutations that are then passed on to offspring.

Physical illnesses previously linked to advancing paternal age include: prostate cancer, nervous system cancer, neurofibromatosis (fleshy growths of abnormal nerve tissue), the most common type of dwarfism, Apert syndrome (malformation of the skull, hands and feet), and Marfan syndrome, which involves defects of the eyes, bones, heart and blood vessels.

"We've always thought of women as having a biological clock, and we've been very aware that as women get older, their reproductive capacity falls off and eventually ceases altogether," said Dr Susan Harlap of New York University.

"We've always thought that men were able to father children basically indefinitely. I don't think anyone had given any thought to whether the children would be healthy. What this study is doing for us is just blowing that idea out of the water."

Dr Harlap, one of the authors, said the findings represented "the tip of the iceberg" in terms of what might be traced to paternal age, saying researchers should examine the influence of father's age in other ailments, such as cancer and heart disease.

Dr Malaspina said older men considering becoming fathers should put the findings in perspective.

"I think it's important to bear in mind that even though children of older fathers have a greater risk of disease, most children are fine." The findings may help explain long-standing mysteries about schizophrenia. The fact that it is remarkably persistent in human populations over time puzzles experts because those with the disease are less likely to mate and reproduce, presumably because of the social effects of the illness. In addition, its incidence is strikingly consistent across human populations.

The study suggests that in each generation fresh genetic mutations replenish the genes for schizophrenia and keep the incidence stable, the researchers say.

As men age, their sperm cells continue to reproduce through division. Each division introduces a slight risk of error in the genetic material of the new sperm, which is passed to the children.

- REUTERS