That getting old reduces your fertility has long been taken as a given by most people. But a study demonstrating the age-fertility link in men is getting an awful lot of coverage today.

A French study of over 12,000 couples receiving intrauterine inseminations, where sperm is directly injected into the uterus, found the long-acknowledged link between female age and lower fertility.

“But we also found that that the age of the father was important in pregnancy rates – men over 35 had a negative effect,” says Stéphanie Belloc, from the Eylau Centre for Assisted Reproduction, Paris (press release). “And, perhaps more surprisingly, miscarriage rates increased where the father was over 35.”

Belloc and colleagues looked carefully at the sperm of the men involved, cataloguing sperm counts, motility and morphology, their results are presented today at the European Society of Human Reproduction and Embryology meeting in Barcelona. She says this is the first time that such a strong paternal affect has been shown and suggests DNA damage in older men may be responsible.

“We already believed that couples where the man was older took longer to conceive, but a number of reasons had been put forward for this,” says Belloc. “Neither was there any definite evidence that miscarriage rates increased when the man was older.”

Most of the coverage acknowledges that a link has been known about in the past, but there is a general flavour of this being the strongest evidence yet.

A review of the literature from 2001 suggests decreases in pregnancy rates of between 23% and 38% between men under 30 and men over 50 but the new press release itself doesn’t put numbers on the drop in fertility so it’s hard to compare it.

In terms of size this is a big study but I can’t be the only one who thinks people attending a fertility clinic may not be the best sample to assess general population fertility in. Time for a massive longitudinal study in the general population perhaps?

More

The LA Times has an in-depth piece from doctor Valerie Ulene about causes of male infertility.

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