Study links older fathers to autism

Dustin Hoffman (right), played Tom Cruise's autistic brother in Rain Man.

Men over 40 are more than five times more likely to father a child with autism than their younger peers, a study has found.

Research involving more than 130,000 children has revealed that the risk of autism rises steadily with advancing paternal age.

But there was no link with increasing maternal age, say the researchers, who included a team from the Institute of Psychiatry at King's College, London.

The finding suggests men have their own biological clock, which affects their capacity to produce healthy offspring as they age, in a similar way to women.

The risk of birth abnormalities such as spina bifida increases sharply with advancing age in mothers but is popularly thought to be unaffected by the age of the father.

But experts say this may be because fathers have not been studied as closely.

"A lot of research has focused on mothers, and fathers have not had the same attention. It may be that the problem is the same [in both sexes] but the research has not been done," said a spokesperson for the Progress Educational Trust, a charity supporting research into fertility.

The new study, published in Archives of General Psychiatry, suggests ageing in men and women may increase the risk of different kinds of birth abnormality.

The research was carried out among 132,271 Jewish children born in Israel in the 1980s by Dr Abraham Reichenberg, from the Mount Sinai School of Medicine in New York, and colleagues from the Institute of Psychiatry in London.

The results showed that among fathers aged 15 to 29 when their child was born, the risk of autism was six in every 10,000 children.

Among fathers aged 30 to 39, nine in 10,000 children had autism (50 per cent higher), going up to 32 in 10,000 (more than five times higher) for fathers aged 40 to 49.

The risk was even higher among fathers aged 50 and over, although the sample size was small.

Dr Reichenberg said: "This research adds to our knowledge that men also have a biological clock when it comes to reproducing.

"The sample size for the over-50s was small so we added it to the results for fathers aged over 40, but our research suggests that very old fathers have around nine times the risk.

"The research shows a linear effect - with every 10 [extra] years, the risk doubles."

Experts believe autism is becoming more common, affecting 50 in every 10,000 children compared with five in 10,000 in the 1980s, a tenfold rise in 20 years.

Better diagnosis has contributed to the rise but there is also thought to be a real increase in incidence. The trend to later parenthood in recent decades could have contributed to the rise.

The authors said several genetic factors could be at play, including spontaneous mutations in sperm-producing cells, or discrepancies in how genes are expressed.

Although the fact all the children were Jewish was a limitation, Dr Reichenberg said he did not believe that affected the results.

- INDEPENDENT