Do Men Have A Biological Clock?

For years, the thinking was that ovaries age but sperm don’t. That’s because women are born with a lifetime supply and their eggs have a limited shelf life. Men, on the other hand, keep churning out new sperm. And with millions to spare, it’s been thought that there must be a vibrant one around.

(You only need one good sperm and one good egg to make a baby)

Now a new study is turning the dogma on its head. Tomorrow at the European Society of Human Reproduction and Embryology in Geneva, Harvard’s Laura Dodge is presenting the results of her analysis of more than 7,000 couples who went through nearly 18,000 attempts of in vitro fertilization. As expected, pregnancy rates declined most among couples when the woman was older than 40. But here’s the shocker: Pregnancy rates were also lower when the man was older than 40 but his female partner was younger than 30.

The age of the woman is still the driving factor—but the new findings show that you can’t discount the wannabe-father’s age. For women between the ages of 30 and 35, having a partner who is older decreased the chances of having a baby by about 11 percent, Dodge found.

“For women less than 30, we saw the strongest decrease when the men were more than 10 years older,” Deacon told me.

She said they did not look for reasons but named a few possibilities: it could be something in the aging man’s DNA; or epigenetics—something in the environment that screws up the sperm-making machinery. The potential reason I found most fascinating was this:

The body has it’s own way of killing off damaged cells. It’s called apoptosis. Think of it as cell suicide. Men have an apoptosis system that weeds out the faulty sperm. If this mechanism isn’t working well with age, it could let some slacker sperm get to the egg, messing up the chances of pregnancy.

So yes, the science titillates me: We may be talking about the body’s equivalent of a defective TSA, a microscopic Transportation Safety Authority, that’s letting some bad guys slip through.

But there was more to it. I couldn’t help feel a gleeful pang of schadenfreude. We women have been worried for years about our aging reproductive tracts—that biological clock ticking away—but it takes two to make a baby—so it makes sense that men’s machinery would get old too.

I really hope that anyone who pays the money to venture into the assisted reproductive baby-making route comes out with a baby. So I see this study not so much as more depressing news when it comes to older parenting but really a sign of hope.

Right now for couples going through the test tube baby process, scientists try to pick what they think is the best egg but take any sperm. “It’s kind of crazy how we just choose one without knowing about the precise mechanism,” Dodge added.

Research like this should drive studies that help doctors select the egg and sperm most likely to make a healthy baby—and boost the success rates of all the pricey baby-making procedures.