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Age and its effect on male fertility remain a tough nut to crack

For years, the impressive case of Charlie Chaplin, who fathered a child in his late 70s, has been the lecture-room example of man's lifelong fertility.

But last Friday, Spanish crooner Julio Iglesias' father trumped Chaplin by announcing he was to be a father again at the age of 90.

While studies have nailed down a significant drop in female fertility from the age of 35, unravelling the effect of age on male fertility is a tougher nut to crack.

"It's been extremely difficult because the older men we need to study tend to be married to older women who have gone through the menopause," said Allan Pacey, a senior lecturer in andrology at Sheffield University, in the north of England.

Men produce sperm for the duration of their lives and indicators such as sperm count and swimming ability change very little with age, which could suggest that male fertility might not dip either.

But that is not the case. In 2000, researchers in Bristol, south-west England, looked at the rate of successful pregnancies among thousands of couples. They found men aged 40 and older were half as likely to get their partners pregnant as men under 25.

"What they couldn't tell was whether it was a biological effect, was it down to the fact that older men simply have less sex, which we know to be true, or that the longer people have been together, the less sex they have," Pacey said.

What is known is that as men age, the DNA in their sperm accumulates damage.

"If the DNA is damaged, they might get fertilization, but the embryo won't develop or it will miscarry" in most cases, Pacey said.

Last month, researchers in California reported a study of 70,000 couples which showed that men aged 50 and above were more than four times more likely to have a child with Down's syndrome.

Other studies have shown an increased prevalence of schizophrenia in children with older fathers.

"Much of the time, we don't see the effects of older paternal age ... The only time we can see what happens is when you get old, rich and powerful guys who somehow have much younger wives," Pacey said.
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