STUDY: Older men's sperm is more prone to genetic defects than that of younger men, according to a new study.

JOURNAL: American Society for Reproductive Medicine

AUTHORS: Dr. Narendra Singh

ABSTRACT: 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.

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COMMENTARY: 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 thirties 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 thirties or forties.

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.

Men concerned about their fertility should avoid activities such as smoking that may damage the DNA of their sperm. 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 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 twenties or early thirties. But the study does alert fertility doctors to another potential problem when older couples have difficulty in conceiving.