No Place for Blame
Biological Clock Strikes for Men, Too - At Age 35
The capacity to blunder slightly is the real marvel of DNA.
- Lewis Thomas
by Mark Henderson and Patrick Barkham
Men who put their career before having a family should beware: the ticking of the biological clock is as important for fertility in men as it is in women. American scientists have discovered that genetic damage to sperm routinely starts to cause infertility in men as young as 35. The strongest biological evidence yet for a significant drop in male fertility in the late 30s is a warning to the increasing number of grey-haired fathers who are leaving it later to have children.
The popular worry that career women risk losing the chance to have children has long been supported by infertility research focusing on how the quality of women’s eggs deteriorates with age. Researchers from the University of Washington in Seattle have now provided the first firm molecular explanation for why childless career men should worry too. The chances of having a baby are reduced if the man is in his late 30s or 40s.
The study, led by Narendra Singh and unveiled at the American Society for Reproductive Medicine conference in Seattle 15 October 2002, examined the sperm of 60 volunteers aged between 22 and 60. All the men had healthy sperm counts. Dr Singh’s team found that, whatever the sperm count, its genetic quality was closely related to age, with a cut-off point for serious damage of about 35.
Men in the older group had higher concentrations of sperm with broken strands of DNA, more acute levels of such genetic damage and their immune systems were much less efficient at weeding out faulty sperm by programmed cell suicide, or apoptosis. The sperm of the older men were also less vigorous swimmers.
Clare Brown, of the British infertility charity Child, said the findings cast new light on the often overlooked problem of male infertility. "About a third of all infertility is male factor," she said. "Male-factor infertility is more prevalent than people think. It’s not generally in the public’s mind that male sperm quality does indeed go down with age, from, as we now see, the age of 35."
William Keye, president of the American Society for Reproductive Medicine, said that men concerned about their fertility should avoid activities such as smoking that may damage the DNA of their sperm. He added: "While there’s nothing anyone can do about getting older, men who want to retain their own best capacity to father children should try to minimise contact with toxic agents and maintain a healthy lifestyle."
The proportion of British men aged over 40 becoming fathers increased by half in the 1990s. In 1999 one in ten children was born to a father aged over 40. The number of children born to fathers over 40 has risen by nearly a third to 42,000 a year in the past 20 years. Older fathers include David Jason, who had his first child at 61, Tony Blair, John Humphrys, David Bowie and Mick Jagger. James Doohan - Scotty from Star Trek - was an 80-year-old great-grandfather when his wife gave birth to his 7th child.
The findings do not suggest that most men who wait until after 35 to try for children will have problems, particularly if the man’s partner is in her 20s or early 30s. But the study does alert fertility doctors to another potential problem when older couples have difficulty in conceiving.
Source: timesonline.co.uk British News 15 October 2002
Hormone Swings Affect Men Too?
by Rachel Nowak
The newly recognised condition of irritable male syndrome plays havoc with male animals, temporarily turning confident, chest-beating Tarzans into withdrawn, grumpy wimps. And there's some evidence that irritable male syndrome, which is triggered by a sudden drop in testosterone, affects men as well as animals, says Gerald Lincoln of the Medical Research Council's Human Reproductive Sciences Unit in Edinburgh, Scotland. The symptoms may resemble those of the so-called male menopause, but Lincoln believes the condition can affect men of any age when stress causes testosterone levels to plummet. If he's right, it's not just women who have their hormonal ups and downs.
Lincoln first pinpointed the syndrome in Soay sheep. In the autumn, the rams' testosterone levels soar and they rut. In the winter, testosterone levels plummet and they lose interest in sex. High testosterone is supposed to mean more aggression. But the rams were more likely to injure themselves when testosterone was low. So Lincoln monitored the activity of eight rams, such as how often they struck out with their horns. As testosterone levels fell, the rams changed from competent males who addressed each other in a ritualistic fashion, to nervous, withdrawn animals that struck out irrationally, he says.
Reindeer and Elephants
Red deer, reindeer, mouflon and Indian elephants also show clear signs of irritable male syndrome when testosterone levels fall off at the end of their breeding seasons, says Lincoln. "The mahouts sometimes starve the elephants after the musth, or tie them up to keep them under control."
But what does this mean for people? Here the evidence is shaky, Lincoln admits. But it's clear that testosterone has a major impact on human behaviour. The brain is loaded with receptors for testosterone and its conversion products. What's more, Richard Anderson, also at Edinburgh, has found that when men who cannot produce testosterone come off hormone replacement therapy, they become irritable and depressed. Their mood improves when they resume treatment.
Lincoln thinks that stresses such as bereavement, divorce or life-threatening illnesses could send testosterone levels plummeting. There are few human studies on stress and testosterone, he says, but numerous studies on animals, including primates, show that testosterone levels fall when stress sends corticosteroid levels skywards.
Men Behaving Sadly
"It's right on the money," says reproductive endocrinologist David Abbott of the Wisconsin Regional Primate Research Center in Madison. "Testosterone effects have been missed. When a bloke gets grumpy and irritable, [researchers] try and explain it only in terms of cortisol levels and depression. They ignore the fact that testosterone levels are probably falling too."
But David Handelsman, an expert on male hormones at the University of Sydney, is more cautious. He says the changes in testosterone levels in normal adult men are far smaller than the dramatic swings seen in Soay rams, with one notable exception: levels fall by at least 90% in men who undergo castration for advanced prostate cancer. "The wives notice it first," says Keen-Hun Tai of the Peter MacCallum Cancer Institute in Melbourne. "The men become more withdrawn, but more emotional. They laugh and cry more easily."
Clearly, the jury's still out when it comes to people. But if irritable male syndrome does affect men, diagnosing it won't be easy. It's far from clear what normal testosterone levels are, while extra doses of the hormone may increase the risk of heart disease. But the syndrome could still be worth investigating. "Instead of putting stressed men on Prozac, a little testosterone may do the job," says Abbott.
Journal reference: Reproduction, Fertility and Development volume 13 page 567
Rachel Nowak lives in Melbourne
Source: newscientist.com 27 February 2002 New Scientist print edition
Older Men: Reset Your Biological Clock
by Tom Blake
Often, when men become single after a lengthy marriage, they try to reset their biological clocks by pursuing women who are 15 years younger - or more. What can a guy expect?
Source: thirdage.com Older single women really want to believe this is true, anyway. But not everyone shares this viewpoint. See also:
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