Able semen: sperm has a shelf life, too (even if Mick Jagger is still going strong)

The rapid decline in womens fertility as they age is well known but what about men and their sperm? Read the fine print and the answer becomes less clear

Some weeks ago, a sperm cell (lets call this little guy Vince) fused with an egg and resulted in a pregnancy. What makes Vince a newsworthy sperm cell is that he came from a 72-year-old penis. And not just any old 72-year-old penis, but the one attached to Mick Jagger, frontman of the Rolling Stones.

I suspect that, like me, women the world over are frowning at their screens as they hear news of heroic lil Vince and the 29-year-old ballerina he impregnated. Because if this headline were about Cher getting ready for a fresh round of diapers, the reaction would range from disbelief to disgust and Cher is two years younger than Mick.

We think that once women are past 35 that their fertility plummets, and theyre less likely to conceive let alone deliver a healthy baby, while men can just keep pootering along until the well runs dry.

Science, on the other hand, isnt so sure.

We know that women typically have their first children at a younger age than men. According to the Centers for Disease Control and Prevention, the average age a woman in the US has her first child is 22.8 years; for men, its 25.4 years. Although both men and women are becoming parents later in life than they were a few decades ago, that gap (and those bonus career years that men get) still persists. And theres a pretty obvious explanation for it: the average heterosexual couple consists of a man thats 2.3 years older than his partner.

OK, but how long can you wait if you want to produce offspring that have your great hair but not that nose? The American Society for Reproductive Medicine (ASRM) has some pretty clear advice in its 2012 handbook for patients.

For the ladies:

A womans best reproductive years are in her 20s. Fertility gradually declines in the 30s, particularly after age 35. Each month that she tries, a healthy, fertile 30-year-old woman has a 20% chance of getting pregnant By age 40, a womans chance is less than 5% per cycle, so fewer than 5 out of every 100 women are expected to be successful each month.

And for men:

Unlike the early fertility decline seen in women, a mans decrease in sperm characteristics occurs much later. Sperm quality deteriorates somewhat as men get older, but it generally does not become a problem before a man is in his 60s.

If you carry on reading, however, you need to pay attention to the not-so-sexy small print. The handbook continues: There is no maximum age at which a man cannot father a child, as evidenced by men in their 60s and 70s conceiving with younger partners. (Emphasis emphatically added.)

Hold your spermy horses! So old men like Jagger do just fine in the fertility game so long as theyre pairing up with young ballerinas? How do we know if its down to outstanding semen or fresh young female eggs?

Well, actually, we dont. Very few studies that look at male fertility have controlled for the age of the female partner, which seems very important given the aforementioned age gap between heterosexual partners.

Theres more bad news: old men can become old dads, but their sperm has a slightly higher risk of gene defects. A study published in 2014 looked at information about individuals born in Sweden from 1973-2001 all 2,615,081 of them and found that children born to men over the age of 45 were three and a half times more likely to be diagnosed with autism and 13 times more likely to be diagnosed with ADHD than those born to men aged 20-24.

Im not going to go casting judgment on others (especially seeing as Im the product of some very old sperm myself), but given the current scientific evidence, Im going to steer clear of the Vinces of this world and focus any future procreation efforts on a younger male demographic.

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