What Happens to a Man’s Sperm as He Ages?

Posted on by Paul Turek, MD
Aging Men’s Sperm
The icy truth about paternal age. (Courtesy unsplash.com)

Make no mistake: Egg freezing to preserve women’s fertility has become a new American pastime. Unheard of five years ago, egg freezing has allowed thousands of women to worry less about their biological clocks and focus more on other dreams and goals. Should men be doing the same?

Just Keeps Ticking

Men, too, have biological clocks when it comes to fertility. Well, it’s really not a “clock” as much as a “sundial” or an “hourglass.” Fair or not, the fertility timeline of men is a much longer one than it is for women. In general, women’s fertility sees measurable declines between 35 years and 45 years of age. Men see similar declines from ages 35 years to 70 years. This difference is because women’s bodies harbor eggs made before they were born, and men make new sperm constantly throughout their lives.

Although men’s fertility potential outlasts that of women, it’s not necessarily a good thing. With all that turning and churning of the sperm-making machinery — putting out 1000 sperm per heartbeat at its peak — things gets taxed, stressed and fail. And what fails first is not so much production numbers but the quality control that goes with it that is so vital for the healthy packaging of the sperm genetic payload known as its DNA.

The Younger the Better

As men age from 30 years to 70 years, here’s how sperm change:

  • Sperm counts stay about the same. Sperm motility falls about 0.5 percent/year.
  • Sperm DNA fragmentation increases about 1 percent/year.
  • The rate of sperm gene mutations increases 8 to 10-fold.
  • The sperm epigenome changes dramatically.

What does all this translate into? More infertility (2 percent/year increase), more miscarriages (2-fold), more preterm births (2-fold), more fetal death (1.5-fold), more birth defects (1.5-fold), and more adult diseases in offspring like schizophrenia (3-fold), bipolar disorder (5-fold), ADHD (6-fold) and autism (5-fold). This then is the hidden risk of being an older dad — more trouble getting the kid and handing off diseases that are entirely new to the family.

Biological Retirement Fund

When should this concern you as a future father? Well, the average age of first-time fathers in America is now 30 years. Some use the term “advanced paternal age” to describe men 40 or older, but others say 50 years old is a better mark. The good news is that most of the paternal risks described here occur at rates far lower than the typical birth defect rate (3 percent) in the U.S. And the increased risk occurs relatively slowly at first, until age 60, at which time it increases at a much faster rate. The bad news is that there is currently no way to test either the man or his sperm for paternal age risk. You either give it a go or you don’t.

To reduce the paternal age risk, the solutions are to have kids early or bank sperm early, similar to women banking eggs. Get the good stuff stored away … kind of like a biological retirement fund. You can even do this in the comfort of your own home nowadays! There may also be solace in knowing that the whole concept of paternal age is brand new to us humans, as we have only been living long enough to talk about it for about three generations or so. So, these issues are not only new to you, they are new to all of us!